Cloth in AM ~ Introduction
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CLOTH IN AM
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INTRODUCTION
Part 2: Defining terms. -
HOW AM CLOTH WORKS
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COLLISION DETECTION
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CLOTH CONSTRAINTS
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SUSPENSION CPS
In the context of Animation:Master, when you want to add clothes to a character, you mean one of two different things:
- adding a model that looks like a particular piece of clothing, like a dress, a sweater, a shirt, a coat, etc; or
- applying cloth technology to a particular model or a region of a model to apply automated secondary animation to that model or region.
Of course, these are by no means mutually exclusive, but they do involve a variety of different rigging and animating techniques and result in rather different final animations.
For the purposes of this tutorial, I will refer to #1 simply as cloth, clothing, clothes, etc while #2 I’ll refer to as AM Cloth, to distinguish between the everyday concept of clothing and the particular technology that AM uses to create a dynamic system of Masses and Springs that control the mesh’s deformation.
Most of the time, a user will not need or even want to actually implement AM Cloth for clothing. Bone movement and its attendant technologies like Smartskinning and Poses will be the preferred method of animating the clothing a character may be wearing more often than not. Gloves and jeans are excellent examples of clothing that, as long as a character is wearing them, don’t require AM Cloth. They are stiff and tight enough that bone animation is going to produce the best results. For items that are just a little looser, Pose animation goes a long way to giving just a hint of secondary motion.
As much as possible, this method of animation should be preferred. AM bone control is the surest way of controlling the behavior of mesh deformation during animation. Using AM Cloth on any part of your model is, in fact, giving up control of your mesh deformation. AM Cloth gets the final word in what your mesh does and you can only influence its movement with parameters and the surrounding objects in your scene. In other words, in using AM Cloth you sacrifice primary bone control for uncontrolled secondary motion.
So why on earth would anyone ever want to use AM Cloth for anything? Well, for one, there are other items of clothing, such as a flowy skirt or a billowing shirt, where trying to control all the motion through bone movement would be tremendously difficult. Secondary motion adds a lot of really great animation, and is one of the chief reasons to use a computer to animate to begin with. Also, control structures can be added in to exert higher and more direct influence on the motion of the cloth giving more controlled, predictable results, and without sacrificing the fun and often very visually gratifying effect of a chaotic system. Finally, and most importantly, using AM Cloth, you gain the advantage of animating through a system, where the motion of one part affects every other part.
This tutorial is then ultimately about adding in control structures to a given model or parts of a model to enable us to use the control of bones with the system of AM Cloth. The use of these control structures will not only allow for controlled Cloth movement in items of clothing, but can also be applied to musculature on a character to create convincing muscle flexing in complex areas of the body, such as the chest, shoulder and thumb.
It also asks a fundamental philosophical shift in thinking from other animation techniques. Muscle animation is simply direct, overt control over the mesh deformation during animation. Bone animation is the first level of abstraction. You tell the mesh to follow certain bones and then tell the bones to move and rotate in space. If you include rigs, Smartskin and Poses, the bones then affect each other according to rules that you establish. But in the end, all they can do is affect each other. The mesh simply follows along obediently with whatever the bones are doing. With Cloth, the mesh reacts to itself by virtue of being bound to Masses. Thus the control techniques are equally different; it amounts to direct control of things to exert indirect control over the mesh. It is then the second level of abstraction.