Hierarchical animations in DirectX and handling seperate animations on the same mesh?

Question

I have a hierarchical animated model in DirectX which loads and animates based on the following DirectX sample: http://msdn.microsoft.com/en-us/library/ee418677%28VS.85%29.aspx

As good as the sample is it does not really go into some of the details of animation that I'd like. For example, if I have a mesh which has a running animation and a throwing animation as seperate animation sets how can I get the throwing animation to occur for bones above the hip and the walking animation to occur for bones underneath the hip?

Also if I wanted to for example have the person lean left or right would I simply have to find the bone for the hip and multiplay a rotation matrix by its matrix? In this case I think the matrix is m_amxBoneOffsets?

Answer 1

Well the thing is the running animation SHOULD affect the throwing animation slightly. What you need to look into is animation blending.

I'm sure Valve wrote a good paper on how they implemented it in Counter-strike many years ago. Its not on the valve site though so I'm not sure where I got this memory from ...

Answer 2

Composing multiple animations to a single one is usually the job of an animation system, something that is way out of scope of the D3D sample.

Let's look at your 2 examples:

running and throwing

Well, in this case you could apply the animation for the lower part of the body from the running animation and the animation for the upper part of the body from the throwing animation. And you'd get a very crappy result.

The how is just a matter of knowing which bones are where in the bone palette (something that depends on how they are stored, and in which order, but nothing inherently hard. The definite reference should be the documentation of the tool generating the animation data)

In practice, you're better off with a blending of the 2 animation. This is, in general, is hard, and software packages exist out there that do this for you. Gamebryo, e.g.

Or, an animation of a running guy who throws is different enough from a standing guy who throws that you might be better off having 2 animations.

Leaning

If you apply a rotation matrix to the root bone, you'll simply rotate your whole character. Now if you rotate the next bone in the hierarchy (from the spine), you'll get all the bones that depend on it to rotate likewise. It will probably do what you want, but there's a sure way to find out. Try it!