MODELING BASICS

In this section, your goals are to learn what a model is and how to construct one. It covers the basics of splines and patches and how to manipulate them. Some of the information from section 1 is also reviewed. Some intermediate concepts such as spline connectivity and continuity will be covered, along with important tips on what not to do when modeling. Rotoscopes and their use in the modeling process are also introduced.

The plan of attack is to understand splines and the A:M modeling tools in the context of simple modeling projects before moving on to more complex things.

By the end of this section, you should have a model of a floursack (the sack of flour is a long-standing tradition for animators) that can be used to work through sections 3 and 4 (bones and actions). Hopefully, you will gain an understanding of what splines are capable of, and how to lay control points and manipulate bias settings to achieve surface topology.

Sections covered:

Activities for your porfolio (when finished with each exercise, save it into your porfolio in the AM_ch2 folder*):

Skills Emphasized:

Concepts Discussed: Tools:

SPLINE PATCH BASICS

What is a spline? Because A:M uses them exclusively in modeling this is a very good question. The nontechnical answer: A spline is a curved line used by A:M to define a surface. This line is defined by a set of points in a connect-the-dots fashion. These points are defined by you and are called control points (CPs). The math behind what a spline is and how it functions is complex and not something taught here. Luckily, splines can be used without knowing the equations behind them. Most importantly for us, splines are the most basic building blocks of the patch.

What is a patch? A patch is how A:M defines its rendering surfaces. A patch is defined in the software by a simple rule: three or four CPs on two or more splines. Every valid surface on a model must conform to this rule. Areas defined by more than four CPs or by points that lie on the same spline are considered holes in a surface and will not render.

Many 3D programs use the polygon as the basis for creating surfaces; this has some inherent problems that splines and patches avoid. Spline patches have an unlimited resolution, meaning that no matter how close you get to an edge, it will always be a perfectly smooth curve. Polygons, on the other hand, have a fixed resolution, and getting too close to an edge will reveal resolution-based faceting. Spline patches also animate deformations very well, in part due to their infinite resolution. The ease and power of the A:M animation tools are a direct result of this. Polygons are rigid by nature and can shear and twist at joints unless additional resolution has been added.

Are spline patches perfect? No. Surfaces that crease or get lumpy are some of the more common issues that spline patches have. Most of these problems can be dealt with by learning how patches work and how to adjust them properly. For those hard-to-fix areas, there are mesh-smoothing materials and methods that are discussed later. Due to the nature of patches, some of tools that you might 1;>e used to if you have a background in polygons, aren't there. This is a matter of acquiring the mindset required by patches. There are also certain modeling tasks that can be faster or more easily accomplished with polygon-based tools. This is one of the important lessons of 3D graphics: there is always some form of tradeoff. For the ease of animation that A:M provides, you have to sacrifice some of the benefits of polygon modeling.
So put your modeling cap on and do this: Open A:M and create a new model (if you need to, go ahead and refer back to section 1 on how to create new objects in A:M). Before you attempt something ambitious, learn how to make patches and get a feel for navigating the workspace. The following exercise is designed to do just that.

CREATING PATCHES

Remember: three or four points on two or more splines. This means that before you can have a patch of any kind, you need at least two splines. Draw two splines. Using either the Add button or the A key on your keyboard, activate the Add/Stitch tool.

Make the first spline V-shaped with six points, as shown in Figure 2.1. Simply click in the modeling window six times, once for each control point you-wish to lay down. A:M will automatically draw a spline through the points you create. Once all six points are drawn, press the Esc key or right-click to stop drawing points.


FIGURE2.1 A U-shaped spline with six control points.

These six control points all lay on one spline, which is indicated by the curve that the spline takes as it moves through the points. It just also happens to be the default way A:M connects CPs when using the Add/Stitch tool. In order to make this spline into a patch it must have some of its control points connected to a second spline to form a "closed" area surrounded by at least three, but no more than four, CPs.

There are a number of ways to connect points along splines, but for now you are looking at the easiest and most direct way. Click the Add button again, and this time draw a four-point spline, as shown in Figure 2.2. Click once to the left of the shape, once on the control point circled and marked 2, once on the control point circled and marked 3, and once to the right of the shape. With the Stitch tool, clicking on a point automatically connects the point you are drawing to the existing point. You will look at how this works and some other aspects of the Add/Stitch tool in a moment.


FIGURE 2.2 The second spline will be used to close the patch.

Verify that this is indeed a rendering patch before you go any further. Again, there are a number of ways to do this. The most direct method is changing the draw mode of the modeling window to shaded or shaded with wireframe. Do this by using the number keys along the top of the keyboard (not the number pad) from 7 to O. Press 7 to set the mode to the default draw mode of the active window (this can be any other draw mode or a combination of them for windows with multiple objects in them). Press 8 to force wire frame drawing (typically the default for modeling; so you won't see much of a change from 7 to 8 most of the time) on all objects in a window, regardless of their default. Press 9 to change the draw mode to Shaded, which uses the real-time 3D of your computer's graphics card to display surfaces as if rendered. It is imperfect, but useful for getting a general idea. Press 0 to get' the same shaded view with the wire frame of the model drawn on top. You will use this last mode frequently, while modeling, to see the surface more clearly as you manipulate the points that comprise it.

You can also change the draw mode of a window by control-clicking (rightclicking on the PC) inside the window and choosing the desired setting from the contextual menu under View> Render Mode. The keyboard shortcuts tend to be much faster; so it is recommended that you use them instead of the contextual menu in this case.

Choose either Shaded or Shaded Wire frame now. The space between the four control points that make up your patch should turn white indicating that there is a rendering surface (see Figure 2.3).


FIGURE 2.3 A rendering patch.

Before you go on to look at other ways to create patches, here is a little information about the nature of splines and the curve of patches. The curvature of the patch surface is determined by the points that define its edges and the points further along those splines. In your example, if there were no dangling end points there would be no easy way to introduce a curve into this patch: the surface would remain flat at all times. You could only change the orientation of the surface or shear it. (This is actually a very broad generalization and not technically correct, as there are other attributes of a spline that can contribute to its curvature; but those are a little more advanced than you need to worry about right now. We will get to them once you start modeling some actual objects rather than single patches.)

Change the view to Bird's Eye (using the 7 key on your number pad or the contextual menu), and select and move the points that were left dangling when the patch was formed. Once you get into things, understanding how one point can relate to another will be crucial to building surfaces that look good and animate well.

Before moving on, it might be a good time to take a peek at some of the other methods that you could use to make this same patch. When you model objects that are more complex, you will find you use each of these methods at some point or another.

Create a new model. In the new window, use the Add/Stitch tool to draw a four-point spline in the same rough U shape you had before. It will look slightly different due to the lower density. Now, if you simply wanted to close this into a surface, you might think that you could just draw a spline across the mouth of the patch; this would give you four points, but would they be on separate splines? Try this: Use the Add/Stitch tool and make a new spline by clicking on either of the two end points of your U. What happens? If you clicked on the points themselves and not off in space or on the spline further along, you would, see that they have indeed connected to the end points and there is a spline between those points, as in Figure 2.4. If you switch to shaded mode, however, there is no patch here


FIGURE 2.4 Four points on a single spline do not make a patch.

What happened? Instead of creating a new spline between the two end points A:M continued the spline: What you actually have here are four control points that lie along a single spline. While they enclose an area, they do not follow the Patch creation rule because there is only one spline. If you want to add a new spline attached to an end point you have to inform A:M that you don't want the default behavior. (Once you start talking about spline continuity, in modeling you will see how continuing a spline is a very helpful default.) You do this by modifying the default behavior of the Add/Stitch tool with a modifier key.

Select all the points (press Ctrl+A PC, Command+A Mac) in the model window and delete (press the Delete key) them. Draw the four-point V-shape again, and this time when you want to add the closing spline across the top of the shape, you will modify the tool. Click the Add/Stitch tool button or use the A keyboard shortcut. Before you click on anything, press and hold down the Shift key on your keyboard. Keep the Shift key down, and click on the end points of the V shape. When you have clicked on the second point, release the Shift key and press the Esc key to stop drawing points. Do you notice anything different about the shape? Compare the two shapes in Figure 2.5: One was created without the Shift key and the other was created with the Shift key.


FIGURE 2.5 The difference of the curves shows that one spline is a
continuous loop while the other is not.

Note: the spline continues in a smooth continuous curve through the unshifted version, whereas the shifted version has a sharp corner on each of the end, points. This sharp corner indicates, among other things, that the spline does not continue through the point; rather, there are two splines that abut here. If you are still in Shaded mode, or switch to it now, you will see that a patch was indeed created.

By holding down the Shift key, you have told A:M to override the default behavior of the Add/Stitch tool and to abut these splines, rather than continuing the original one. Now there are two separate splines and four points, which conforms to the rules of creating a patch.

Look at yet another way you can create this patch. Go ahead and create a new model. This time, create two separate splines and join them together manually, without the benefit of the Stitch tool. Start with the same six-point U-shaped spline that you created for your first patch. Then above or to the side of that spline, create a four-point spline that goes from left to right, as in Figure 2.6. It is important that you don't click the U-shaped spline or its end points. You have two distinctly separate splines, and in order to build a patch, you need to tell A:M that some of the points on these splines should be connected in order to form a patch. You do this by using the Weld function.


FIGURE 2.6 Start with two separate splines.

Click the point circled in Figure 2.7 in order to select it. Be careful that you just click it rather than dragging a selection box around it. In order to connect this point to the U shape, you must position it over the control point that you want to attach it to. Click and drag the point down until it sits over the point you want to attach it to (indicated with the arrow in Figure 2.7). Without releasing the mouse button press the tilde key (-) for Mac users, or right-click. This is the Weld command. The points are now connected. Go ahead and drag them around to make sure.

To connect the other side of the U and close up the patch, repeat the process with the CP circled in Figure 2.8. If your window is still in Shaded mode, you will see the patch form as soon as you close it. If it is not, change draw modes now to verify that your patch is valid.

Believe it or not, there is at least one more way to make this single patch, and for the sake of completeness we will look at it now. This is basically the same technique as the first patch you made in this tutorial, but instead of having the six-point U shape to start, you will use the Stitch tool to create new points as you add the second, closing spline.


FIGURE 2.7 Start by dragging this point in
and welding it to the U-shaped spline.


FIGURE 2.8 Close the patch by dragging
and welding this point to the U-shaped spline.

Either select all and delete or create a new model. In the window, draw a four-point U-shaped spline (see Figure 2.9) with the Add/Stitch tool.


FIGURE 2.9 Start a new patch with a fourpoint spline.

So far, so good. You have seen how you can use the Shift key to close off this shape with a second spline and get a rendering patch. But what if you want to add a couple points to the U shape, so that the dangling ends remain? There are a number of ways to do this (which we won't get into for the moment), but the easiest is to use the Stitch functionality of the Add tool. Simply click the Add/Stitch button or use the keyboard shortcut (A); click once to the left of the U shape, then click on the original spline where you want to add a point (see Figure 2.10). This creates a new point on the U spline and welds the spline you are drawing to it, all in one easy step. Click the spline on the opposite side of the U (see Figure 2.11), then once to the right, and press the Esc key or right-click to stop drawing the new spline. If you are not already in Shaded Wireframe mode, change the window now and look at the patch you created. It should look like Figure 2.12, which looks exactly like Figure 2.3.


FIGURE 2.10 Clicking the spline between control points adds a new point.

 


FIGURE 2.11 Clicking again on the opposite leg closes off your patch.

 


FIGURE 2.12 The final patch with dangling spline legs.

You should have the idea that there are a wide number of ways in which you can create new patches, and as easy as it is, there are preferred methods and spline layouts. While any three or four points can define a surface, there are optimal layouts of splines that give the most control over a surface. The most stable is a regular grid of four-point patches, as shown in Figure 2.13.


FIGURE 2.13 The basis for a "perfect" patch.

The basis for what makes this grid stable and ideal for creating surfaces in A:M lies in the construction of the individual patches in the grid.

The perfect patch is not just a component of the four points that mark its edges. Since A:M uses the points along the length of the spline to determine curvature, the points outside the patch are equally important. In fact, the perfect patch resembles a tic-tac-toe board (see Figure 2.14). The four points in the center define the bounds of the patch, and along with the eight points surrounding them, define the curve of the surface of the patch. A grid network then creates a set of interdependent surfaces that, when laid out properly, will create a smooth rendering surface. Of course, there are inherent difficulties with this, but for now it is just important that you understand the concept.

The regular grid of patches is so perfect, it is be the layout you will want to use whenever possible. We look at how this is done as you progress and explain the places where you can get away with less-than-perfect splinage. For the moment, however, the focus is on making models with as many perfect patches as possible. It all starts with being able to construct the perfect patch itself.

*(Save your work in your AM_ch2 folder)

The Perfect Patch

Adding in the splines that create this patch happens the same way that you drew the patch in your first tutorial. However, what you want to create is a little different. Start by making a single spline in a rough line from top to bottom with four CPs (see Figure 2.15).


FIGURE 2.14 A game of tic-tac-toe,
or the foundation to good splinesmanship?

This is one side of the perfect patch; there will be three more of these to build. The second one is simply a duplicate of the first, but spaced to the right or left (your choice). Start by selecting all the points in the first spline you drew, either with the bounding box drag, or the Select All keyboard command (Ctrl+A PC, Command+A Mac). While the points are selected, copy (Command+C Mac, Ctrl+C PC) and then paste (Command+V Mac, Ctrl+V PC). An identical version of the original selection should paste, slightly offset, from the original. While the new spline is still selected, position your cursor over the bounding box. It will change to indicate that you are about to move the selected CPs. Click and drag the copy to the side. Now all that remains is to fence in your patch. Again using the Stitch tool, create a spline exactly like the one you made in the first patch tutorial by clicking to the side and then on the two CPs at the top of the spline (see Figure 2.16), and finally one point to the other side, creating a sort of H shape. Once the fourth point is created, press the Esc key or right-click to stop drawing points. Repeat the process on the bottom of the shape, enclosing the four center points to form a perfect patch, as in Figure 2.17.


FIGURE2.15 The single spline is often the start of a model..


FIGURE 2.16 Lay in a new spline with the Stitch tool

Play with this patch and its dangling splines to get a better idea of what patches are made of and what defines their curves. This understanding will be crucial to becoming proficient with patches. Notice that the closer the CPs that make up this patch are to an even plane, the flatter the surface of the patch. If you move one or more of the dangling CPs back or forward, the patch takes on a greater curve along that spline's edge. If you could build every surface entirely out of four-point patches exactly like this one, even in all aspects, then there would be few to no difficulties in modeling. The four-point patch, however, is not always a practical solution, and shapes often require uneven patch sizing and distribution. As you progress, we will explore techniques to minimize the problems that arise when straying from this ideal.

Single patches are, in and of themselves, thrilling (and no doubt you could make them all day and never tire of it), but most people have more ambitious creations in mind when they buy A:M, so let's take your knowledge of the patch and examine how to build basic primitive shapes. In the following tutorials, you are going to build a cube, a sphere, and a torus (doughnut).


FIGURE 2.17 The 16 points in this patch make the perfect spline surface.

These shapes are all 3D solid primitives that will teach you a few lessons about how the tools work and will reintroduce you to the two fundamental modeling tools: Extrude and Lathe. You won't typically create these shapes often, but the knowledge behind them will help you understand how to build masses from splines.

*(Save your work in your AM_ch1 folder)

The Cube

The simplest cube can be created from the perfect patch from the previous tutorial. This cube won't include beveled edges or other aspects of advanced modeling, but it will be a fast and easy way to introduce dimension to your patch.
If you have closed or deleted the model with the perfect patch in it, reopen it or create a new one in a new model. (Creating a new one just for practice wouldn't hurt anything mind you.)

In order for this to be a perfect cube, the points need to have some precision, meaning that the initial shape needs to be as close to a perfect square as you can make it. We will use the A:M grid to put the points into alignment. Start by selecting the four points that make up the corners of the patch, as in Figure 2.18. Notice that the eight dangling points are not selected. It really doesn't matter if you have them selected for this step, but later you will want to be certain that they are not included in any selections. Inside the bounding box of the selection, bring up the contextual menu by control-clicking on a Mac or right-clicking on a pc. Choose the function Snap to Grid from the menu. (You could also use the apostrophe (') keyboard shortcut and not bother with the contextual menu at all.)


FIGURE 2.18 Select just the inside four points.

Snap to Grid will move any selected CPs in to the nearest intersection of the grid, which is displayed in the modeling window (presuming you haven't turned it off in the preferences). If they are spaced fairly evenly, they might be in a perfect square. If they aren't, simply deselect the group, turn on Snap Manipulator to Grid, and move the offending control points to the appropriate grid intersection. You have to use the Snap Points to Grid function first, because, as you may remember from Chapter 1, Snap Manipulator will only move points by grid units from where they happen to be positioned. Once the points have all been positioned, turn off the Snap Manipulator mode.

Now that you have established a square, proceed to a cube. Make a selection of the four center points again (if you had to deselect them in the previous step; but note that the eight dangling control points cannot be a part of this selection, or you will run into some problems). While the group is still selected, click the Extrude tool button or use the keyboard shortcut (E). This will extrude the points once, which, if the preferences for this are still at the default, will position the points -10 pixels in the y-axis (see Figure 2.19).


FIGURE 2.19 Default settings offset the extrusion -10 pixels in the y-axis.

When you extrude, A:M helpfully makes the newly extruded points the selection. In order to make your shape a cube you only have to move this selection into position. Move the extruded points up to match the original box by pressing the Shift key and the up-arrow key. This will move the selection up 10 pixels.

The arrow keys will "nudge" a selection 1 pixel at a time along the same plane as the viewport. Holding down the Shift key will nudge the selection 10 pixels.

Change to a right or left view by pressing the 4 or 6 key on your keyboard's number pad, and move the selection back (or forward if you prefer) in the z-axis until it is roughly as far back as it is tall (see Figure 2.20). If you want it perfect, of course, you can use the Snap Manipulator to Grid function, but it is preferable to just nudge the shape back with the arrow keys until the grid shows that it is roughly correct.


FIGURE 2.20 Moving the extruded group back in the side view
gives you cube dimension.

If you had to move the front points much out of line with the dangling control points, the front edges might show some curve (see Figure 2.21).

To iron this curve out, you can either peak all the points on the cube or simply delete the dangling points. Peaking the points is done by selecting the entire object and clicking the Peak tool button (keyboard shortcut P). Either way you go about it, the result should look like Figure 2.22. If it isn't already, put the window in Shaded mode to get a look at your handiwork.

The simple six-patch cube teaches a lot about how patches are formed. Notice that the sides and rear of the cube were built as legal patches when you used the Extrude tool. This is because your extruded selection was in itself a patch. The Extrude tool creates a new group of splines and points with the same continuity as the original. If the extruded group had been a hole (four points along a single spline, for instance), the resulting model would have been a box-shaped tube with no end caps. Try extruding closed splines that are not patches, and notice how this behavior is different. When modeling, it is important to know exactly what the tools are creating; and when you look at internal patches, you will see a good example of why that is. Put your cube aside and examine some other primitive shapes.


FIGURE 2.21 If the points are not on a plane, the splines may curve through them.

*(Save your work in your AM_ch2 folder)

The Sphere

Creating a' perfect sphere requires a perfect circle. Hand-drawing splines to achieve this is more likely to create heartburn than a sphere. Luckily, there are ways to create perfect circles without resorting to antacid.

Start with a new model window. Instead of the Add/Stitch tool, use the Add Lock tool to draw a two-point spline to one side of the y-axis at a slight angle (see Figure 2.23). By default, there is no button for the Add Lock tool, so use the Shift+A keyboard shortcut to invoke it. The Add Lock tool will only draw twopoint splines, and it is used by clicking and dragging. The point you click becomes a point, and a spline is drawn out from that point in the direction you drag. When you release the mouse button, the second point will be positioned. If you simply click in the window you will see what looks like a single CP with no spline, but in reality, there are two points on a single spline exactly on top of each other.

A control point cannot exist without a spline. At bare minimum, you can have two control points with a spline between them. If you delete the CP at either end of the spline, then A:M would remove both points and the spline as well.


FIGURE 2.22 The finished cube.


FIGURE 2.23 Draw a simple two-point spline.

Once the two-point spline is in place, you are going to Lathe it to make a rough conical shape: two circles, one above the other, with straight splines drawn between each CP to make the walls. The Lathe tool always creates circular spline rings, with, by default, eight cross sections. In order to use the Lathe tool, you need to give it something to work with. The Extrude tool, for instance, needs a group of points in order to work (try extruding a single CP; it just won't work). What the Lathe tool needs was discussed ih Chapter 1, but now is a good time for a quick refresher.

A real-world lathe is a machine into whith a piece of raw material is placed and spun along an axis, then cutting tools r9move portions to create a profile. A wood lathe, for instance, might be used to _reate balusters for a handrail on a staircase; by using a pattern, a number of it_ms can be cut to exactly the same profile. The Lathe tool in A:M uses the sanie basic idea to create shapes from spline profiles. You create the pattern (profil_), and then use the Lathe to make the shape solid. The axis around which the material rotates is the y-axis of the modeling window by default. As your spline is set up to work from the default, there is no need to change that. (You will eventually want to lathe something not on the axis line; then the axis of the Lathe tool is explored further.) The only other thing that the Lathe tool needs to know is which spline you want it to work with. The key word here is spline. You tell A:M what the focus of any tool is by making it selected. This is true of all the modeling tools, as well as the data tools for the PWS, and so on. Therefore, with the Lathe tool, you need to indicate which spline is going to be used as your pattern. The easiest way to do this is to simply click a single point on the given spline. If you drag a bounding box around a CP (even if that CP exists on only a single spline) then A:M is not focused on the CP/spline, but rather the group that you indicated. This is not acceptable because a group selected this way can contain multiple splines on differing planes. A:M needs to know where the lathe "pattern" is in relation to the axis. (This can seem odd, but it is important to understand. As was quickly shown in Chapter 1, there are ways to select groups and still have the Lathe tool available. This is covered in more detail when you start working on complex models.) If the wrong type of data is selected, then the Lathe Tool button will be grayed out, indicating that lathing is not currently possible.

With this information in mind, simply click one of the two points on your spline, and then click the Lathe button (or use the L keyboard shortcut). A:M will use this pattern to create the conical shape we discussed (see Figure 2.24).

What you have are two perfect circles, but for your sphere, you only need one. Select and delete the top ring of CPs by dragging a bounding box around the whole ring, and press Delete on your keyboard to leave just one circular spline without any rendering patches. This will be the basis for your sphere. Effective lathe patterns describe only half of a profile. You need to get rid of half of this circle so that the Lathe tool can do its job properly. Change to a top view (press 5 on the number pad) so you can see the full circle. Select all the CPs on one side of the x-axis line (by clicking and dragging a bounding box around them), and delete them, what remains should be a semicircular, almost gumdrop-like shape (see Figure 2.25).


FIGURE 2.24 The Lathe tool creates a rough cone that
will give you a perfect circle.

This is not exactly what you want, but it is close. What you need to do is to open the flat edge of the semicircle. For this, use the Break Spline tool. Select the point circled in Figure 2.25, and note on which side of the CP the spline is highlighted.

If the spline is highlighted on the flattened leg of the spline, then you are ready to break, If not, you need to change the selection. Do this by pressing the Tab key (if more than one spline passed through this point, you could select each of them by pressing Tab in succession). Press the Tab key once, and the green highlight changes from one side of the CP to the other. Once the correct side is highlighted, click the Break tool button or use the keyboard shortcut (K) to break the spline and open the flattened edge. What you have is an open semicircle, which will be the pattern you give the Lathe tool for the final sphere (see Figure 2.26).

Drag a selection around the whole spline, and bring up the Rotate Manipulator (by clicking the Manipulator button or pressing the R keyboard shortcut). Rotate the selection 90 degrees in the x-axis, using the red handle of the manipulator or typing the value in the group's properties (either on the Properties panel [see Figure 2.27] or in the Manipulator Properties Widget [see Figure 2.28]).


FIGURE 2.25 Select the circled point to prepare to break this spline.


FIGURE 2.26 The semicircle that remains will lathe into a perfect sphere.


FIGURE 2.27 The Group properties in
the Properties panel.


FIGURE 2.28 The Group properties in the Manipulator Properties Widget.

Switch back to the front view to get a better look at things and return to the standard manipulator by pressing the R key again (or clicking the Standard Manipulator button). Without deselecting anything, nudge the whole shape off the y-axis with the left cursor arrow (or use the right cursor arrow if you have deleted the left half of the original circle). This is done so that the points on the ends of the lathe don't overlap, which would cause a pinched or creased look at the poles of the sphere. After nudging the spline over, deselect it using either the Esc key, the Return key, or simply by clicking outside the bounding box in the modeling window. Select any single CP on the spline. Be careful to only select the CP by clicking on it. Dragging a selection around it or group-selecting it will leave the Lathe tool unavailable (as previously discussed). Simply clicking a CP selects a particular spline, and this is the information that the Lathe tool uses to do its job. Once you have a CP selected, click the Lathe tool. Insert the Lathe tool icon here or use the L keyboard shortcut to make the final sphere. The result should resemble Figure 2.29.


FIGURE 2.29 A perfect sphere.

As perfect as it looks, this sphere has one minor flaw. If you zoom in to the poles of the sphere you can see that there is a small hole at each end of the sphere. In most cases this is not a problem (and can even be helpful for some modeling tasks). If the hole is too large and can be seen clearly without zooming in, you can make it smaller. On the other hand, if you want or need to close those holes you can stitch in a couple a splines to close them. The problem here is that adding the points needed to close the top of this sphere will change the way the splines run through the existing points. This will cause a noticeable surface artifact at the pole of the sphere (see Figure 2.30). Masking this artifact is a two-step process that starts back at the half circle that you lathed to create the sphere in the first place.


FIGURE 2.30 Closing the top of the sphere
can lead to noticeable artifacts.

Surface artifacts are not indicative of a flaw either in you or in A:M. Rather, they are a fact of life when working with patch surfaces that you must learn to deal with. At least half the challenge of modeling with patches is coming to terms with, and conquering, bumps, lumps, creases, and other anomalies.

Start by repeating all the steps up to the point where you are ready to click the Lathe button so that you have a semicircle like the one in Figure 2.26. Before you lathe this shape, think a little about what you want to do in order to close it and how that will affect the shape of the finished sphere. Look at Figure 2.30 again, which shows a sphere that was simply closed with the Stitch tool and indicates the problems you are trying to avoid. Notice how the splines that continue across the center point have a different curvature than those that dead-end. This is because the additional point in the middle is now influencing the shape of those splines that connect to it (as discussed in the section about the perfect patch). But you may ask: "What if we continue the points that dead-end through the center as well? Wouldn't that change their curvature to match and alleviate the surface anomalies?" The answer is: It might, but it will cause other problems that are even more difficult to repair. The problem with this approach is that you now have four splines crossing at one point, creating an area of three-point patches. For the math behind a patch, this creates some areas of uncertainty on how the patches should be smoothly rendered. The result is creasing, and in addition to the original four splines that had changed their shape, the remaining four have now joined them in their oddness (see Figure 2.31).

What this situation calls for is an increase in the density of the control points at the poles of the sphere. This is something you will need to add in manually before you lathe the shape. In order to buffer the transition from side to poles you will need two extra points at each end of the semicircle. You can add these points by simply clicking on the existing spline with the Add/Stitch tool (keyboard shortcut A). But you want to modify the behavior of how A:M deals with adding points to a spline.


FIGURE 2.31 Continuing the remaining splines across the
pole causes more problems than it solves.

Without getting to far into the complexities at this point (you get to them soon enough), look at how adding a point to the spline changes the spline itself. In a new window, a three-point spline has been drawn (see Figure 2.32), which can be thought of as an arc from your sphere. Some adjustments have been made to the bias to make it mimic the sphere more closely (we discuss bias in great depth shortly, but for now you need to be aware that something has been changed).


FIGURE 2.32 A three-point mock-up of your arc.

When you click the spline with the Add Lock tool and stitch in a new point, what happens is that the bias does not remain consistent. indeed, the shape of the spline is altered (see Figure 2.33). You want to tell A:M not to alter the shape of existing splines when you add in a new point. This is a modification of the default behavior, which you may guess requires the use of a keyboard modifier. When you want a spline to maintain its curvature, use the Shift key to modify the Stitch tool's behavior (in the same way it modified the way the tool handles connectivity).


FIGURE 2.33 Adding a new point with the Stitch tool
will change the curvature of the spline.

With this knowledge, go back to the semicircle and add in the points you need. Click the Add button or use the A keyboard shortcut (before clicking the spline, hold down the Shift key). Now click the spline near the pole of the semicircle template. This will add a new point and maintain the curvature of the current spline. Press the Esc key (or right-click) to stop drawing points, and use the modified Stitch tool one more time to add a second point to the top pole. Now repeat this process for the bottom of the semicircle. When complete, you should have a spline similar to Figure 2.34. Now when you lathe this template you have more spline density at the poles of the sphere, which helps maintain the shape when you continue the splines across them.

Dead-end splines can be a major source of creasing and other artifacts. It is best to avoid them whenever possible.


FIGURE 2.34 Modifying the Stitch tool allows you to
add a point to the spline and maintain its curvature.

Go ahead and lathe the semicircle to make the basic sphere, and close the top. Once lathed, zoom in close to the top of the sphere so you can see the hole in the pole. At this point, closing that hole is a simple application of the Stitch/Add tool (which you should be familiar with by now). Your resulting splinage should look something like Figure 2.35. Note that the splines do not cross across the top of the pole.


FIGURE 2.35 Changing the spline layout across the top of the
sphere solves most of your problems.

The reason for this is that you want to avoid as many patches with dead-end splines as possible. This layout of splines creates only two patches with dead-end splines, whereas crossing the pole would create four.

Now, if you zoom out and put the window into Shaded mode, you will notice some artifacts on the surface near the pole, as in Figure 2.36. This is a direct result of the splines that dead-end rather than continuing through the pole, but you don't want to continue them because that would cause other problems. So what should you deal with these artifacts? A:M has a special material called Porcelain that is used to tell the renderer to smooth out surfaces. It is an extremely useful material, and you will use it more than once as you progress through the modeling tutorials in this book.


FIGURE 2.36 Even with new spline layouts,
dead-end splines cause artifacts.

First, add the material to your project. This is done by right-clicking on the PC or control-clicking (for Mac users with single-button mice) the materials folder. Choose Import Material from the contextual menu. The File Open dialog will appear. Navigate to Data/Materials/Geometry/Porcelain.mat, and click OK. Once the material is loaded into the project, all you have to do is drag and drop it from the Materials folder onto the Model name in the PWS. If you are in Shaded mode, you should see immediate results, as in Figure 2.37. With the application of the Porcelain material, the closed sphere is complete.

The porcdain mateterial is used so often you might want to consider addIng it to your library for quick access. Just drag and drop it from the project workspace into the library window. Then in the future all you need to do is drag and drop the material from the library directly into the model window.

The sphere is one of the more useful primitives, as it lends itself to organicshaped characters well. The techniques you just practiced will be used extensively in the creation of characters. In addition, you have already covered the basic use of just about all the major modeling tools that A:M has to offer, but there are some twists, turns, and slightly more advanced topics that need to be discussed before you can have a complete understanding of splines.


FIGURE 2.37 The Porcelain material will smooth out the
remainder of our surface irregularities.

Continue your exploration through the creation of primitive shapes.

*(Save your work in your AM_ch2 folder)

THE TORUS

Torus is the technical name for a doughnut shape. You will be building one in A:M as a way to demonstrate the use of the group pivot. Start exactly as you did with the sphere: Lathe a cone and delete the top. You should have something resembling Figure 2.38.

From here, use the Lathe tool to fill out the remainder of the torus. In order for the Lathe tool to create a torus, you need to override its default behavior. If you were to simply select a point of this circle and lathe it, it would look like nothing had happened, but selecting a spline and translating it reveals Figure 2.39. The Lathe tool took your circle and lathed it around its own center point creating a many overlapping CPs, splines, and patches. Not at all what you want.

There are two ways you can handle this situation. First, move the splines into a position that allows the default lathe function to create the shape you want. Second, change the defaults the Lathe tool uses in order to create the shape you want without altering the splinage. For the this shape, either would be fine; however, since the learning focus here is on the pivot, opt for the second method.

Adjusting the pivot is an essential modeling technique, giving control not only of the lathe but also the way manipulators behave when using them to affect the mesh. Pivot is a property of a group (visible in the Properties panel or by showing the Manipulator Properties Widget), and requires a group selection in order to be set. This presents a problem as the Lathe tool, by default, is a function performed on a single spline as indicated by one CP, meaning that it is unavailable to groups.


FIGURE 2.38 The torus begins from a lathed circle.


FIGURE 2.39 Letting the Lathe tool decide how to
handle this situation created more of a mess than anything.

However, you can select a group in such a way to preserve the spline information that the Lathe tool needs in order to do its job. Make your initial selection by simply clicking a control point. This selects a spline (indicated by the green highlight along the spline), which provides the lathe its information for the template. You can maintain this information (and expand your selection) by using the Spline Selection tools-complement, spline, and select all connected, represented by the comma and backslash keys, respectively. This creates a group selection that allows the Lathe tool to function, while at the same time allowing you to adjust the pivot and alter the way the lathe functions.

Select any control point on the circle you made earlier, and use either the comma or backslash keys to create a group. Once the bounding box indicates that a group has been selected, the next step is to gain access to the pivot point of the group and move it to a more desirable location. The pivot can be seen in any group selection indicated by the Y-shaped RGB axis indicator, initially located in the center of the selection. The axis indicates the local axes of the current group and can be changed; when the mode is set to one of the manipulators other than standard, such as rotate, the pivot can be manipulated without altering the position of the control points. You can use Translate or Scale as well, but rotate is more intuitive. When a group has been selected, the Lathe tool will use this pivot to determine the axis of rotation rather than the default axis of the Modeling window.

Bring up the Rotate Manipulation tool and switch to a Bird's Eye view to get a good look at the pivot. Look at the axis indicator at the center of the manipulator. Note that the ends of each axis and the center of the indicator have square "handles" (see Figure 2.40) called pivot manipulation handles. If you place your cursor over any of the handles it will change from the standard arrow to one of the pivot manipulation icons, either rotate or translate.


FIGURE 2.40 The pivot handles give
control over many modeling operations.

Remember what these icons look like so you can know from any view when and how you will be adjusting the pivot. The handle on the end of each axis will rotate the pivot in the axis corresponding to the color of the handle. The yellow handle in the middle of the pivot will translate the pivot. The pivot can be translated two ways-by hand or by numerical precision. Numerical precision can be given to the pivot by using the manipulator's properties box or the Properties panel. For your purposes here, simply clicking the yellow pivot translation handle and dragging it to the left of the circle spline will suffice. You will want to move it far enough that the pivot completely clears the circle (see Figure 2.41). Notice that the Rotate Manipulator expands as the pivot is moved, indicating the new range that it will turn. Lathing this ring now still won't give you the nice doughnut shape you are after. Since the Lathe tool uses the y-axis to perform its rotations, we would instead get a very confused flat disk shape.


FIGURE 2.41 Move the pivot to the side of the circle.

The pivot must also be rotated so that the axis of the lathe will sweep the circle around as the hull of the shape. The easiest way to picture how the lathe will work is to imagine the green-handled y-axis ring of the Rotate Manipulator as indicating the future hull of the object, meaning that the lathe will function concentric to that ring. You need to rotate the pivot around so that this ring is in the right position. Mouseover the Blue Pivot Rotation handle and rotate the pivot 90 degrees in z. Then do the same for the x-axis. Looking down on the manipulator from the top view, the green-handled y-axis ring should run straight across the screen from left to right, bisecting the circle you want to lathe.

Once the pivot is in the proper position, click the Lathe button or press the L keyboard shortcut. You should have a perfect torus, as shown in Figure 2.42. If not, undo and try again.


FIGURE 2.42 The finished torus.

The pivot has more uses than adjusting the Lathe tool, although that is one of its most important. Depending on the active manipulator, it changes the way the current group behaves. For the Rotate Manipulator, the connection is easy to make: The pivot changes the arc that defines how the current group will move. The Scale Manipulator moves all selected points toward or away from the pivot; so moving the pivot changes the vector that the points will follow during a scale operation. Also, points closer to the pivot will move less than those farther away, which maintains a basic approximation off the curve of splines as they scale. This allows scale to maintain a basic shape but "flattens" it as points approach the pivot.

The Rotate Manipulator can also be used as a Skew tool when used in conjunction with some more modifier keys: the axis limit keyboard modifiers. When manipulating a group or object, the 1, 2, and 3 keys across the top of the keyboard (not to be confused with the numeric keypad, which is used to switch views) limit movement to the X-, y-, and z-axes, respectively. If you hold down more than one key you will be able to move the selection in all the axes you have activated (Le., pressing 1, 2 will allow X and y; pressing 1, 3 will allow X and z). When using the standard manipulator this generally means that the selection will translate in only the selected direction (or directions, if more than one modifier key is held down). This is used frequently in Choreography mode to constrain the movement of an object to one or more axis. When used in Modeling or Muscle mode, along with the Rotate Manipulator, these keys will cause the selected control points to be skewed as they slide along the constrained axis. This skewing is, as might be expected, centered on the pivot point.

Creating simple shapes, such as these geometric primitives, can be thought of as breaking down the surface to its basic shapes (a circle, a square, and so on) and determining the optimal shape for that surface in splines, then following through with the tools.

*(Save your work in your AM_ch2 folder)

SPLINE BIAS

Unfortunately, not all shapes are this simple. When striving for realism, even cubes require more than an extruded box. Bevels and other surface irregularities require an understanding of how splines behave, going through control points and across surfaces before they can be convincingly executed.

The way a spline moves through a control point is determined by several factors. You have already discussed how adding points affect splines and examined how peaked or smooth control points can change a surface. Here, how peaked and smooth control points relate to spline bias is explored, which no doubt raises the question: "What is spline bias?"

Simply put, the bias of a spline defines the mathematical parameters that A:M uses to define the curvature of a spline in and out of a control point. That sounds complex, and in reality it is, but you don't need to understand the math behind bias in order to be able to use it to affect a spline. Bias consists of three numbers that you can edit: magnitude, gamma, and alpha. Each of these numbers controls a different aspect of a spline's curvature as it passes through a point. All three types of bias can be adjusted by typing numerical values into the properties of a control point (more on how you can show and select those properties later) or adjusted by the use of interactive handles in the Model (or action in Muscle mode) window. Here are some simple definitions you need to learn before you progress to a simple example of their use.

Magnitude is the most commonly used bias adjustment for models. It defines how strong a curve may go through a point: At a magnitude of 5, it may appear almost peaked, while a magnitude of 300 produces a stronger, rounder curve (see Figure 2.43).


FIGURE 2.43 The magnitude of a CP affects
the "strength" of a spline's curve.

To adjust the bias of a CP, use the bias handles. Turn them on with the Show Bias button. Pulling the handles to make them longer or shorter will adjust the magnitude of the CPo To get numeric precision, type a value into the Properties panel or PWS for the selected CP under the bias disclosure triangle. Often, it is more convenient to use the Manipulator Properties box, which presents data on the selected items in a Model window, changing its context based on the current manipulator. The Standard Manipulator gives the xyz coordinates for the selected CP, and if the Show Bias Handles button is depressed, the current bias settings.

The Lathe tool automatically adjusts the magnitude for points that make the circumference of the rings to make each ring a smooth circle. Magnitude can smooth corners or it can create a bulge in a surface.
Gamma can be difficult to understand, yet it is crucial to have an understanding of why it behaves the way it does before it can be used effectively in modeling. Once mastered, however, gamma can be a potent tool in your arsenal.

The why of gamma isn't very complex, but unless someone tells you how it works, it can be an impenetrable mystery. Recall that a spline going through a CP has its curve determined not only by the control point that it passes through (by the bias settings of that point), but also by the control points on either side of it, along the spline. Look at Figure 2.44. Here is a simple three-point spline with bias handles showing on the middle, selected CP.


FIGURE 2.44 The bias handle has a logical point of reference.

Note the angle of the bias handle in reference to the spline. At first, this seems to be arbitrary, but it has a logical point of reference. If you draw a line between the two CPs on either side of the selected point you would see that the bias handIe at a gamma of 0 runs parallel to that line. Call this the gamma reference line (see Figure 2.45). Any adjustment to gamma is an expression of how far off parallel the bias handle is moved in degrees. Gamma can be changed simply by dragging the bias handle, or you can specify numerical precision by the methods discussed while talking about the magnitude (Properties panel or Manipulator Properties box).

If you want to adjust just the magnitude and avoid accidentally tweaking the gamma (or alpha) of a spline, hold down the Command key (Mac) or Ctrl key (PC). This locks out the gamma and alpha. Likewise, holding down the Shift key will lock the magnitude to one side of the CP.


FIGURE 2.45 The gamma of the bias handle is related to
the parallel line between the adjacent CPs.

Alpha indicates how far off the centerline a bias handle is when compared to the gamma reference line (see Figure 2.46). Its use is more difficult to grasp than gamma or magnitude, though, and it is used less frequently.

Bias Handle


FIGURE2.46 The alpha/gamma reference line relationship.

Alpha is used to turn the direction of a spline, to control the shape of a leg muscle, for example. Sometimes a large gamma adjustment can make splines running though them play out to one side or the other; alpha can be used to counter this side effect and bring the splines back in line. (This is used primarily on mechanical models and to maintain lower patch counts on curves.) Note that alpha's rotation is tied to the gamma, and the greater the gamma, the less movement the alpha seems to have. To understand this phenomenon, look at how alpha works in relation to gamma.

Imagine that perpendicular to the gamma reference line, running straight up through the control point being adjusted, is an axis. This axis is immoveable and always remains perpendicular to the gamma reference. The tip of the bias handle describes the radius of a circle around the axis, which represents the rotational path of the alpha (360 degrees given as -180 to 180). This circle also remains parallel to the gamma reference line. As the gamma raises or lowers the bias handle, this circle is narrowed.

Therefore, when manipulating alpha on a CP with a high gamma setting, the effect seems limited but is actually just moving in a smaller circle. Indeed, a gamma of 90 would make the alpha appear to not move at all.

Let's put some of this to work. You have already modeled a simple cube (emphasis on simple). Take that example to the next level, and at the same time introduce an important concept in mechanical modeling: the beveled edge. Bevels are important in that they help define a shape by giving light a surface to interact with along the edges of an object. Without bevels, your models will look less realistic (which is fine if that is what you are going for) because they will lack crucial specular highlights.

The Beveled Cube

The simple six-patch cube is easy enough, but modeling for realism requires the use of beveled edges; A:M has no automated beveling tools (well, that's not 100% true; when discussing modeling wizards, ways to introduce automatic bevels will be shown). Plan and lay down your splines with the bevel in mind.

Start by laying down a rough, rounded, square-shaped loop (see Figure 2.47), using the grid points as a guide. Don't worry about making it perfect yet. That will be taken care of later with judicious use of the Scale tool. Simply draw nine points with the Add Lock tool, connecting the last point to the first.

Select the loop and extrude it. Move the extrusion back up in y to line up with the original shape. Without deselecting, switch to the side view and move it back in the z-axis to give it depth. So far, this is pretty much what you did for your fist cube, except that the ends of this cube are not capped off (because you did not start with a rendering patch). You still have to cap the ends of the shape manually (see Figure 2.48).


FIGURE 2.47 The outline of the cube already has
bevels planned into its spline layout.


FIGURE 2.48 After extruding, move the new ring
back to form the sides of the cube.

Now make a single four-point patch with eight loose CP ends as you did earlier. Make the spline ends roughly match the points of your original loop. Select the new patch and all its CPs, and move it forward in the z-axis. Copy it and paste it, and move the new patch to the back of the cube. These will be the end caps (see Figure 2.49).


FIGURE 2.49 Two four-point patches will cap the ends of your cube.

Take each of the points dangling from the four-point patches and attach them to the corresponding points on the tube you extruded earlier. This is your rough cube shape (see Figure 2.50).

It's a basic cube, but not perfect. You need to introduce precision to clean this shape up. Simply select all the points on the cube and snap them to grid (via the contextual menu or the' key).

Depending on why you need the beveled cube, you might want the bevels to be flat or rounded. To flatten out bevels, simply peak the entire shape and leave the bias handles alone. This simple shape is the basic building block for many objects: office buildings, tables, chairs, and so forth.

If a more rounded bevel is desired, the gamma and magnitude of each spline must be adjusted. Since the sides need to remain flat, it makes sense to peak the splines for this operation as well. A peaked spline gives control to the bias on either side of the control point independently of one another, allowing you to set different curves in and out of a point.

Start with the gamma. Make sure your bias handles are visible and select any point that comes off the face of the cube onto the bevel. You want the selection to be along the spline that runs across the bevel; if it is not, use the Tab key to move through the splines that pass through that control point until you have the correct spline selected.


FIGURE 2.50 The completed rough cube.

Right now the bias handle should be running right along the spline. You will want to pull it up so that the gamma runs parallel to the face of the cube instead (see Figure 2.51). For this cube, a gamma of about 45 will do the trick (or a -45 gamma depending on the spline). Once the gamma is in place for all of the splines, you can adjust the magnitude to round out the edges as much as you need.


FIGURE 2.51 The gamma should be
parallel to the face of the cube.

Throughout your gamma and magnitude adjustments, it is important to notice that the sides of the cube shape remain perfectly flat, thanks to the peaked control points. This technique of peaking points and adjusting gamma is used quite frequently in mechanical modeling. When you are finished, you should have cube similar to Figure 2.52.


FIGURE 2.52 The finished beveled cube.

*(Save your work in your AM_ch2 folder)

COMMON SURFACE PROBLEMS

While learning how to model, you will encounter problems with creasing, artifacts, and lumpy surfaces. These are often because the result of incorrect splinage or bad patch-making decisions. This section will cover some of the more common problems and offer some general solutions to overcoming them.

Three-point patches are best to avoid, if possible. They have their uses but if the area they are placed isn't ideal for them, they can cause creasing. If an area seems to need a three-point patch, reconsider the splines to see if it cannot be resolved with a four- or five-point patch (more on five-point patches later). There are times when you want a crease-in the corner of a mouth or an eye, for example-and three-point patches can do the job nicely.

Connecting more than two splines at any junction of a mesh will also crease (see Figure 2.53). Considering that a patch takes its curvature from the CPs that make up the ideal patch sheds a little light on why this is the case. When there are more than two splines crossing at a single control point, the math must estimate the surface, which lets creases slip in. If a set of splines must cross like this, either find a good place to hide them or rethink the mesh.


FIGURE2.53 More than two splines intersecting will cause creasing.

Some four-point patches can also cause creases (see Figure 2.54). A spline that doubles back on itself can create a legal four-point patch, for instance, but any splines that come off of it are going to cause creases. It is better to continue a spline until it terminates.

Four-point patches that are too close together can also cause creases and lumps on the surface of the model. Careful adjustment of the bias of splines that are bunched closely together can help eliminate this creasing. However, that is a long and tedious process. Radical changes in the proportions of patches will cause lumps and creases. Areas of small dense patches must transition into areas of larger patches gradually.

Splines that are not connected by the ending control points maintain their separate nature, allowing noncontiguous splines in modeling. Deleting the tails and continuing to model will guarantee creasing. Ideally, splines should terminate only at radial holes in the mesh. Care must be taken with the Extrude tool as it preserves continuity (or lack thereof), making for a lot of potential work to fix creasing models.

Avoid internal patches. An internal patch causes render time errors on the outside of a model, which can be particularly frustrating and difficult to understand. To avoid internal patches, it is necessary to know what causes them. Remember: any three or four points on two or more splines define a patch. This can include areas inside the model. For example, when a surface has been built with valid patches, extruding that surface will generate valid patches in the extrusion. This is to be expected and can be used to advantage in some instances.


FIGURE 2.54 Some legal four-point patches can cause creasing.

If, however, you extrude a surface more than once, the first extrusion forms a valid patch that is retained when the second extrusion is made. This creates a patch that exists entirely inside the surface of the model. It is impossible to see this unless the model is in Wireframe mode (8) and the surface normals are showing (show normals with the Shift+l keyboard command). Look at Figure 2.55. See those little lines? Those are surface normals. What a surface normal is and how it works is more than a little complex. For the purpose of this example, if you see a normal, that means there is a surface connected to its base. If you look closely, you can see one in the center of the object, indicating the surface of an internal patch (circled for clarity). To get rid of that internal patch, make the splines that form the middle ring a single spline. Or, if the density of splines there is not necessary, delete it.

These are some of the most common issues that cause creasing, or other render artifacts. Avoid them and your models will get smoother and smoother. There is, of course, the whole art of learning how to optimally place your points and splines to generate smooth surfaces, but that's what years of practice are for. Right?

Spline Continuity

Often, you will have portions of a model to join: arms to a torso, for example. How do you run the splines to achieve the best layout, maintain the animatability, and avoid surface creasing? Spline continuity is your guide in making these decisions: Splines should continue as smoothly and naturally as possible.

Joining separate splines is as easy as joining the two by the control points at their ends. In some cases, a CP can pick from two splines to continue. The logic behind which spline will continue is sometimes hard to predict. To determine which spline you are continuing, add a single two-point spline to the model and attach it at the questionable joint. If it extends the spline you had intended, great. Attach the new end to the continuing spline, and delete the extra point. If, on the other hand, it continues the spline you did not intend, attach the continuing spline to the junction. It will now continue the other spline as you had wanted. Delete the extra point and continue modeling.

SPLINE CONTINUITY

In this tutoriaL you are going to attach two perpendicular cylinders, forming a sideways T shape (this is a common joint and can represent a shoulder, for instance). You start with the tools we have discussed here and finish it in the next section.

Start by lathing two tubes, as shown in Figure 2.56. Note the number of sections the first tube has. The three in the middle are intended to allow enough density to join the second tube to it. The second tube was lathed where it sits by moving and rotating the pivot.

Your next step is to find splines that can continue as easily as possible. Look for splines that line up from one object to the other. Figure 2.57 indicates your ideal candidates. These splines can continue across the surface without changing direction drastically and will maintain a continuous spline layout.


FIGURE 2.56 These two tubes are ready to be joined.


FIGURE 2.57 Look for splines that can easily continue.

To attach the horizontal tube without creasing or causing internal patches, a hole must be made in the vertical tube. Select each of the control points surrounding the area where the tube will be attached in turn, and use the Break Spline tool to open a hole (see Figure 2.58). This allows you to tie the horizontal tube in, with continuous splines.


FIGURE 2.58 A hole is opened using the Break Spline tool.

To tie the two together, use the Add tool to draw single splines, and join each end of the spline to the two points you decided to continue (see Figure 2.59). They are now a single spline.

But you still have holes in the mesh, instead of a smooth transition. Make a decision as to what to do with the splines in the horizontal tube. You can tie them around, by drawing splines and adding control points around the horizontal tube. You could delete the remaining splines. You could run the splines down the tube, but all of these still leave holes in the mesh. What to do? For now, run the splines down the tube, as shown in Figure 2.60. Do this by inserting a CP along each ring where you want your new splines to run. Then draw a three-point spline with the Add Lock tool, and attach it to the two new control points and the appropriate spline end on your horizontal tube. Do this for each spline that is to be continued.

The 5-Point Patch is a specialized tool to close holes that would otherwise require lots of spline rerouting or potential crease-causing splinage. The tubes in your tutorial present just such a problem. Where the two tubes intersect, the splines will always create holes offive points at the junction.


FIGURE 2.59 A simple spline can tie the two shapes together.


FIGURE 2.60 Run splines down the length of the tube.

To finish your model, simply select the five points that make up the holes, and click the 5-Point Patch button. The hole is now specified to be a rendering patch. Do this for each hole.

Five-point patches and hooks

"Wait a minute. . . five-point patch? Where did you come up with that? Isn't the rule three or four points on two or more splines. . . what gives?" Okay, that was a little fib to get you started, but as with most things there are exceptions to the rules. In A:M, the exceptions come into play only when you explicitly tell the software to make them. In this case, you except the rule when you select five points that would normally indicate a hole, and click the5-Point Patch Button.

While they are extremely useful, and in some instances practically required, there can be disadvantages to using five-point patches. In order to use them effectively, it's important to understand how they are best implemented.

When a five-point patch is rendered, it is broken up into five areas that are individually tessellated to create the surface. This process is not as informed about the curvature of your surface as typical four-point patches. Five-point patches tend to flatten out or crease when given a highly curved surface to cover (see Figure 2.61).


FIGURE 2.61 Five-point patches tend to flatten out on a highly curved surface.

In addition, it is important that the patch is as close to a regular pentagon as possible. Flattening out any edge of the area can cause problems with creases when the patch is rendered. When a five-point area is encountered that is more square than pentagonal, as shown in Figure 2.62, a hook is a better choice. This doesn't always mean for certain that it will artifact at render time, but why take the chance?

You can also create a patch by dead-ending a point into a spline in what is called a haole Hooks are typically used to ease a mesh of higher density into a mesh of considerably lower density. You create a hook by attaching it to anyspline between two points, rather than connecting it to another point or stitching it onto the spline.


FIGURE 2.62 This five-point patch would be better served as a hook.

You can't just click on the spline and be done with it. That would stitch the point to the spine, creating a new point. What you need to do is click to the side of the spline just off in space, and then escape the Stitch/Add tool. Now that you have a point hanging in space doing nothing, drag it over the spline and weld it in place as you would to connect to points (press the - key on the Mac or right-click on the PC while dragging).

There are three points that can be hooked into: the 1/4 mark, the 1/2 mark, and the % mark between two CPs. After the hook is created, it will maintain its relationship between the two control points on either side of it. This mak\s hooks animate able to a certain extent. Up to three hooks can be attached to a spline.

Like five-point patches, hooks need to be used with some amount of caution. While they can average themselves between control points easily, they are problematic for rotations at joints. Hooks should not be placed on areas that will twist or bend excessively in one direction.

*(Save your work in your AM_ch2 folder)

MODELING A FLOUR SACK

In traditional animation, the flour sack is used to teach animation because it is a simple, unintimidating form that most people can draw without difficulty. This simplicity allows the student to focus on creating the illusion of weight and convincing movement. In the grand tradition of animators everywhere, you are also going to start with a flour sack for very similar reasons: its shape is easy to model and will give you an object to work with as you progress.

Rotoscopes

Animation:Master gives you a tool that you can use to trace over images to get models working quickly. This process is called rotoscoping, after the traditional animation term for tracing animation based on live footage. Rotoscopes, like most things in A:M, can be assigned to the model in a number of ways. You may add one with the contextual menu. Choosing New> Rotoscope will allow you to use any image already in the project or allow you to browse your hard drive for any image you like by choosing the Other... option. If there are no images in your project, the Rotoscope menu item will be followed by ellipses indicating that an open file dialog will let you browse for an image to use. If you already have a rotoscope image in the project, simply drag and drop it to the Model window from the PWS. You can do the same from the Library window's Images tab. A dialog will ask if you would want add the image as a decal or a rotoscope. Select rotoscope, and click OK. This adds the image to the model window as a rotoscope for the current view. If you dropped the image on the front view, it will be visible only in that view; switching to the right, left, top, bottom, or back views will not show the image. Once you have an image added, there will be an item added under the model object in the PWS. This is the rotoscope object (see Figure 2.63) It is named Rotoscope 1 by default, but you can change its name to something more recognizable if you want. More importantly, though, are the two icons that follow the name in the PWS: the hand and the eye indicate pickability and visibility, respectively. These are actually toggles in the PWS, and clicking them will change the state of the rotoscope. The status of the toggle is indicated by either being crossed out or not. A red X through the hand icon, for instance, means that the rotoscope is not pickable (cannot be selected with the default selection tool in the Modeling window). Similarly, a red X through the eye icon indicates that you will not see the image in the window at all.


FIGURE 2.63 The rotoscope item in the PWS is
followed by visibility and pickability toggles.

If you select the rotoscope item in the PWS and look at the Properties panel, you will see the properties that define the rotoscope (see Figure 2.64): where it is located, what size it is (translate, scale), what image it uses, as well as the properties of that image (most of the image properties are not used for rotoscopes; you will look at them more when surfacing is discussed). Some of the more important properties. are the ones that define what view the image will be shown in and how it will be shown. If, for example, you dropped the rotoscope for the front of your model into the left view, you can simply change the view property to place it into the correct viewport. Transparency allows the background to be seen through the rotoscope, or if you enable the On Top property (placing it above any objects in the workspace window), it will allow you to see the model through the rotoscope. The final property-Include in Alpha Buffer-is used for rendering and is not typically something you need to worry about with rotoscopes for modeling.


FIGURE 2.64 The properties for rotoscopes.

Start modeling your flour sack by adding a rotoscope to a new Model window. Import the sack_front.tga file in the images folder on the network into the model as a rotoscope. Once the image is in the window, select it, and open the Properties panel (press command+2 Mac, or Alt+3PC.) The front flour sack image should be visible in the front view; if for some reason it isn't already, set the view property to Front. You may notice that if you switch to any other view you will not be able to see the rotoscope. This is because it has been assigned to only be viewable from the front view. You want to look at the image as your reference, but you don't want to accidentally pick it or move it in the view, so you need to change its properties. Click the gloved hand and it will change to have a red X drawn over it, indicating that the rotoscope is not pickable. Add a second rotoscope this time for the left view using the sack_side.tga image, also on the network. In order for these two images to work together to provide an accurate reference, make certain that they are lined up and the same size in the model window.

To test this:

Once the side-view rotoscope is lined up, make it nonpickable and switch to the front view. It is time to start laying down our splines.


FIGURE 2.65 The guides should rest along the top and bottom
edges of the rotoscope drawing in the front view.

Splining the Flour Sack

Draw one spline in a loop using as many points as needed to trace the shape of the rotoscope image. This line will be your outside guide, and in a way, dictates the final density of your mesh. (But you can, of course, remove or add points later if the model needs them.) Keep the number of added points to a minimum. Overly dense meshes cause lumpy surfaces and are difficult to adjust later on. Make certain that one point at both the top and bottom of the spline is on the centerline of the model, and try to have points on both edges in the same number and in roughly the same places. This will make filling in the mesh easier as we add depth to the flour sack.

Once the outline in the front is complete, do the same for the side view. There are a couple things to think about and be aware of when you draw the side-view loop. First, you want to give the loop the same amount of detail as the side of the front loop. Remember how you were told to keep the density from top to bottom on the first loop the same and positioned in the same place? Same thing here, except front to back; and you need to consider the first loop's density. If you have five points down the side of the front loop, then you should have five points across the front and back of the side loop. Second, make sure that you don't inadvertently stitch the side spline onto the front. In this instance, you want to weld the connections between the front and side yourself. You should have two splines similar to Figure 2.66


FIGURE 2.66 The two loops that will define the shape of the sack.

The CP that you are connecting will jump to the same position as the one to which you are welding it. This is normal and something that can be used to your advantage. Drawing any arbitrary spline can be placed onto an existing set of splines by merely selecting the point that is not in line and connecting it. When working from a Bird's Eye view, splines are almost never drawn in place, but rather to the side, so you can see where you want them. The danger exists of connecting a point that was in the proper place to one that was not. This is something that must be considered as points are connected.

Once these two splines are drawn, go to a Bird's Eye view and connect them. Since the first spline was drawn in front view and the second in side view, the shapes should meet exactly at the middle of the object. The topmost and bottommost CP of each shape should come close to overlapping. Select one of them and weld it to the other.

Now all that you need to do is to route the splines that will fill out the patches for your shape. Thanks to the magic of computers, you only worry about filling in splines for half of your sack. Your number-crunching friend will take that half and make it a whole later.

Building any mesh breaks down to simply adding splines, attaching them, and inserting control points as needed. Rather than always drawing in every spline, sometimes you can reuse an existing spline in other parts of your model. Since the first vertical section is already in place, has the necessary basic shape, and the correct number of control points, using it to fill in the other sections makes a lot of sense. Select any CP along the vertical loop and use the comma key to select all points along that spline. Copy it to the Clipboard (Command+C on the Mac, Ctrl+C on the PC) and paste it back into the Model window. Presuming you haven't changed the default settings in the Options panel, the new ring will be -10 pixels down in the screen and will be an exact duplicate of the first ring, with the important distinction that it is not attached to the mesh. Move the new ring up and over to the next control point on the main body loop similar to Figure 2.67.


FIGURE 2.67 Move the second ring up and
over to the next point on the main body loop.

Repeat the process to add enough rings to go from the middle to the last control point before the ear of the flour sack. The result will look something like Figure 2.68.

From this point, it's very much like a connect-the-dots puzzle. With the Stitch tool, simply click the points along each vertical ring that lines up, going from the middle of the shape in the front to the middle in the back. This can be done entirely from the Bird's Eye view, and that is often the simplest way to goabout things, as it allows you to stay in one view to stitch in all the points.


FIGURE 2.68 Fill out the spline rings to cover the front of the sack.

Activate the Stitch tool either with the Add button on the Modeling toolbar or press A on your keyboard. Choose one cross section of the sack and, starting from the back center point, click each point that marks that cross section until you reach the front center point. Press the Esc key to exit the Stitch tool, and then repeat the process for the remaining cross sections.

When finished, you should have a rough half flour sack shape, as shown in Figure 2.69. Tweak this half a sack until pleased with its shape. You might want to make some broad changes to the shapes in the sack. If so, you might find the Distortion box helpful.

If you want to distort just an area, group-select the control points and enter Distortion mode. If you want to distort the entire model, then just enter Distortion mode without making any selection. The control points and splines in the model will now be drawn as if they were locked with a 3 x 3 x 3 (this is the default; you can change this on the Modeling tab of the Options panel) controllattice drawn around them. By pulling this grid around, the model underneath it can be sculpted to a better shape. The lattice pushes and pulls all the CPs in the mesh to follow along. Any operations that can be performed on a normal model can be performed on the lattice: bias adjustments, Scale, Rotate, and Translate manipulators all work the same.


FIGURE 2.69 The first half of the model can be tweaked until you like the shape.

Say. for instance. you want to plump out the belly of the sack. To do this. select the lattice points that surround the belly. including the ones inside the model, and bring up the Scale manipulator. Position the pivot inside the body in line with the lattice there and scale the lattice up in the z-axis. This pulls the points that are already furthest from the center of the body forward. first bulging out the belly just as you want. Shape the lattice until satisfied with the shape of the model. Exit Distortion mode by clicking the Modeling Mode button (or press the F5 hotkey).

Once you are done modeling the first half it needs to be prepared to copy/flip/attach to make the whole model. For this. you need to get the centerline of the model to run along the y-axis and to be as even in the x-axis as possible.

Before worrying about that though, get rid of the extraneous bit of spline that made the outline loop in the front of the model. Because you modeled just one half of the sack, you have half a loop that is not used. and would cause nothing but trouble if left in place for the copy/flip/attach (C/F/A) operation. You could delete the points on that side of the model but that would leave a spline to be broken before you could continue. Believe it or not, there is a faster and easier way to remove that bit of spline without deleting it. If you recall. when you started with the vertical loops of the sack when you copied and pasted the first loop, it came into the mode not attached to the mesh. You can use that same behavior to your advantage here. Simply group-select all the points that you want to keep (whichever half of the model you filled out but not including the empty front loop). Copy this section (press Command+C Mac, Ctrl+C PC). Before you paste it anywhere, group the remaining points with the '/' key (group-connected). Now all the points should be selected. This might sound a little crazy, but delete all the points. Don't worry; you still have a copy of the part you want in the computer's clipboard. Simply.paste the half you copied back into the Model window, and you will have the sack sans the empty front loop with no splines to break.

This might seem an odd way to get rid of a single spline loop, and for a model like the sack, you could probably remove the spline by hand without any problems. However, if you were working on a larger, more complex model and needed to remove one or more splines to prepare for a C/F/A, then this technique would save you a lot of time and frustration with stray splines. Now to finish up the sack:
Select any control point on the vertical centerline loop of the model. Be sure the spline leg that is selected runs along the centerline loop. If need be, use the Tab key to move through the splines, which pass through the control point. Once the spline is selected, use the comma (,) keyboard shortcut to select all CPs on this spline. This will have just the centerline of the model selected. If you find that one of the cross sections was selected instead, that means you had the wrong spline leg selected at that CP.

When this group has been selected, look in the Properties panel for the scale properties, and scale the group to 0 in the x-axis. This aligns all the points on that spline. Alternatively, you could show the Manipulator properties with the Show Manipulator Properties Widget, and press S to bring up the Scale Manipulator (or click the button on the Manipulator toolbar). The Manipulator Properties widget will change to reflect the numeric values of the current manipulator allowing you to type a scale value directly into the Manipulators Properties panel.

With the group (and spline leg) still selected, check the pivot for the group. Take note of the X value for the pivot and enter its opposite value into the X translate property. If the pivot is at negative .12, translate the selection to a positive .12 in the x-axis. This places the selected group exactly on the X0 mark. Again, if you are using the Manipulator Properties Widget, you can see and manipulate all this information directly in the widget.

Note that you can avoid the Translate step entirely. It is done here to show you how to ensure that the centerline is x-0 and how to adjust it if it isn't. To avoid this whole issue, set the Pivot to 0 in the x-axis before scaling the center loop down.

It is important to note that during this entire process the original spline leg that was used to select the first ring was never deselected, which is why the comma and backslash keys were used. This spline leg indicates to the program which axis and along which spline the copy/flip/attach operation should follow. One of the more common problems with copy/flip/attach operations is not having this spline leg selected or deselecting it somewhere during the process. Select the entire model with the backslash key. Bring up the contextual menu inside the bounding box for the new selection and choose copy/flip/attach. If the splines are set up correctly, the operation should result in one whole model of a flour sack, as shown in Figure 2.70. If copy/flip/attach didn't work, undo, set it up, and try it again.

Modeling half a model and then applying copy/flip/attach is a common method. It not only speeds up your modeling work, but also gives you mirrored control points that are used for pasting mirrored data when setting up muscle poses and Smartskin.


FIGURE 2.70 The finished flour sack.

Finally, prepare your model for bones and animation by moving it so that the bottom of the model rests along the x- and z-axes in the Model window. This will place the model on the same level as the ground in Action and Choreography windows. If this character were a human or animal you would want the feet to be on the ground. So select all the points in the model (Ctrl+A PC, Command+A Mac) and nudge them up with the up-arrow key until the base of the sack rests on the red axis line in the front view. Be careful not to move it in the Y axis as that will put the points out of mirrored alignment and can cause problems later. This is why you use the arrow key rather than just dragging the group in the model window (although there are ways to constrain a drag operation on points, but that is explained later.)

*(Save your work in your AM_ch2 folder)

USING THE MODELING WIZARDS IN A:M

Modeling in A:M can be simple, but there are also repetitive tasks and tasks that are complex and require numerical precision that only a computer can achieve. These types of tasks are encapsulated into wizards. Only the wizards that ship with A:M are discussed here. There are third-party plug-in wizards that you might look into on your own; or if you are a programmer and there is a task that you feel a wizard would be perfect for, the A:M software development kit (SDK) can give you all the information you need.

A:M has six wizards: Sweeper, Grid, Font, AI" Extruder, and Duplicator. The wizards are broken down into two basic categories: those that are used primarily to generate meshes from nothing, and those that are used to manipulate existing mesh.

The mesh generators are Grid, Font, and AI. These are accessed by controlclicking (right-clicking on the PC) the model in the PWS and choosing wizards from the Plug-ins heading. You will see Extruder in this list as well but it is actually a mesh manipulation wizard.

The Grid Wizard (see Figure 2.71) generates mesh grids. The wizard can be used to create flat mesh grids or (by adjusting the scale and magnitude settings) wavy, undulating, terrain-like grids.


FIGURE 2.71 The Grid Wizard interface.

The settings for the wizard are self-explanatory. A width and height in the unit of measurement that A:M is currently using (cm by default) is specified. The step width and height are set, indicating how far apart the grid will space the splines. The axial orientation of the grid is indicated-xy indicating a top view, xz a front view, and yz a side view orientation. The terrain group's magnitude settings will increase the undulation amount, and the scale will adjust the height of the peaks. Setting magnitude to 0 will keep a perfectly flat grid.

The Font Wizard (see Figure 2.72) creates 3D letters for use in logos or titles, or if you build custom fonts, it can be used to speed modeling of things like nuts or other precise mechanical items.

The use of the Font Wizard is straightforward. The letter or letters to be genera1ed are typed in the text box. Select the desired font, from the available true type fonts on your system and any desired formatting styles.

The pieces settings indicate which portions of the font are created. Fronts, sides, and backs can each be created independently of one another, or together to create a fully enclosed font. The bevels settings specify which portions of the font, if any, are to receive beveled edges and whether those bevels are to be round, flat, inward, or outward, and the degree to which they are beveled.


FIGURE 2.72 The Font Wizard interface.

The bevel settings take some trial and error, as the shape of each font can have different effects.
The subdivide edges settings can provide increased spline density for complex fonts ensuring that the shape generated is accurate. None creates no subdivision and uses the fewest control points to describe the shape; all forces all edges to be subdivided and increases density in curves; auto setting allows Font Wizard to decide how to subdivide any given edge.

The AI Wizard (see Figure 2.73) functions identically to Font Wizard, except you must browse in a previously created Adobe Illustrator file for the shape. This allows any shape that can be drawn in a vector graphics program to be converted into an extruded mesh. For complex mechanical shapes this can be invaluable.

The pieces, subdivide, and bevels settings all work exactly as they do for the Font Wizard. If you are not getting good results, you might want to look online at Jeff Cantin's Font and AI Wizard Tutorials. Jeff has been an active tutorial writer in the A:M community and has created a number of beginning-level tutorials that are recommended reading. You can find the URLs for his tutorials and many others at The ARM (http://www.lowrestv.com/arm).

The second group of wizards-Extruder and Duplicator-requires that there are splines in the model to manipulate. Extruder can be called from either the model's contextual menu or a group's contextual menu. Duplicator can only be called from a selected group's contextual menu.

The Extruder Wizard (Figure 2.74) takes a single spline and extrudes or copies it along the length of a second spline, following the second spline as a path. This requires that there are at least two named groups in the model. To name a group of CPs, select them and look in the PWS. Note the Groups folder under the model has opened and,an item called Untitled has been created. This is the default named group that will disappear once the group is deselected. To keep the group in the PWS, allowing it to be easily selected later by simply clicking its name, select it in the PWS and press F2 and type a new name for the group. This named group is saved with the model.


FIGURE 2.73 The AI Wizard interface.


FIGURE 2.74 The Extruder Wizard interface.

The two groups that must be named for the Extruder Wizard are one describing the shape to be extruded (e.g., a ring or star), and one indicating the path the extrusion is to follow.

These groups are indicated in the two pull-down menus on the Extruder's panel. Method indicates whether the cross section is to be extruded or copied. A copy would be used to get a series of spheres to array along a path. The copies/ extrusions settings indicate how many times the cross section is to be copied or extruded: either a set number of times or a number of times based on the length of the path.

The Duplicator Wizard (see Figure 2.75) can also extrude or copy a group, but instead of working on named groups and following a path, the duplication is performed on a selected group in the Model window.

The options for the Duplicator Wizard indicate how the duplicates are to be placed. Duplication method indicates whether a selection is to be copied or extruded. In general, single splines would be extruded and shapes (such as spheres) would be duplicated. Sweep, translates in a particular axis a particular distance, rotates on a particular axis a particular degree, scales a certain amount until a particular distance, or any combination of the three.


FIGURE 2.75 The Duplicator Wizard interface.

The tumble settings are controlled by the pivot, which is set with translation values in the pivot boxes. Rotate here behaves as in the Sweep section, but takes the pivot as the center of rotation rather than the center of the group. Scale, as its name implies, scales the item, again in regard to the pivot the specified amount. Each operation is carried out once per duplication as specified with the repeat setting.

The Duplicator Wizard can be used to create a set of spiral stairs or a pyramid out of blocks, or to space a set of rivets across the surface of a model evenly.

Sweeper (see Figure 2.76) is similar to both the Extruder and the Duplicator wizards. It moves geometry along a path extruding as it goes. The main difference is in the ability of Sweeper to take the points of the extrusion path into account.


FIGURE 2.76 The Sweeper Wizard interface.

Sweeper is similar to Extruder in that it takes two groups to work with. The first is the cross-section group, which can be any spline shape or a solid piece of geometry (although if you use solid, you will most likely want to duplicate rather than extrude). The cross section must be named in the PWS. The cross section is then duplicated or extruded along a spline path. The wizard is used by selecting the path you wish to extrude along and bringing up the contextual menu. From the menu, simply choose Plug-ins> Wizards> Sweeper. In the Sweeper interface, you select the type of sweeping you want the plug-in to do (either extrude or duplicate) and the method you want it to use (regular, irregular, or parallel). Each type of sweep has its own unique way of handling the spline that will be swept along. Regular adjusts the splines off the cross section to maintain volume and shape as it moves along the path. Irregular does not adjust the cross section and allows distortion to happen as the extruding spline changes. Parallel keeps all the cross sections parallel to one another. The Cross Section pull-down is where you choose the named group that will be swept along the path. Note that, unlike the Extrude Wizard, there is no selection of the extrusion path. Instead, sweeper will use whatever path was selected when you invoked the wizard. You have the option of setting the center of the extrusion on the Model window or the group. This is used to determine the pivot for sweep operations. If you draw your cross section off the origin of the Model window, you will want to use the group setting. Orientation is the view you drew the cross section in. You can choose either top or front, and you must draw your cross section in one of these two views. Keep Axis parallel forces the cross section to remain parallel to either the y- or zaxis (depending if it was drawn from the top or the front). This does not affect the other axes like the parallel type would. Scale and Roll allows you to change the orientation or size of the cross section as it is swept along the path. This can be very useful for organic shapes like vines. Use Regular steps allows you to override sweeper's default behavior, which is to place a cross section at each CP on the path it is swept along and to use a specific number of steps evenly spaced along the path instead.

SUMMARY

This section covered a lot of material and moved pretty quickly. These simple modeling tools can take you months of work to get the hang of completely, but you should have learned enough about splines and how they work to take on more complex modeling than our little flour sack.

We have gone over some of the more common mistakes and problems that you might encounter when modeling, which should arm you with the knowledge to avoid these problems or to find solutions to them. More design-specific modeling is covered in later chapters, focusing on mechanical objects and characters in their own sections. Those chapters will build upon the skills introduced here.

A:M has one of the simplest and most intuitive sets of modeling tools around. Now that you have an understanding of how they work, you are well on the road to creating your own models with them. All that you need now is lots and lots of practice!