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Skinned meshes

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Im about to implement a skinned mesh system in my engine. What do you consider to be the best way of doing this (using opengl), should I do it in vertex programs or in software? And any resources and documents regarding the subject would be greatly appreciated. I don''t fully understand how it works yet. Regards, Lantz

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Look up cal3d at http://cal3d.sourceforge.net/ as an example implementation.

I''m making a skinning animation system at the moment.

I''ve found quaternions to be very useful. Especially when blending different animations together( as they are faster to multiply with other quats than matricies). I''m converting to a matrix before transforming the verts though, as matrices are faster at this.

Quats use up little memory(3 floats for a rotation) with a trick.
sum(pow([w,x,y,z],2)) == 1.0
w == 1.0 - sum(pow([x,y,z],2))

Weights and transforming the verts can be done in hardware through extentions. Haven''t got around to that yet, but it doesn''t look too hard. There are even extentions which can do the weighting for you.

If you have a bunch of cash to blow I''d recommend the book ''Programming dynamic character animation'' by David B. Paull. It has a bunch of code in it, and a working implementation. Allthough the code could have done with a bit of clean up before it was put out. I like his style of admitting to problems he had with implementation very much. The explanations are very good.

''Computer animation'' by Rick Parent is ok. Not a practical book at all. It does have some more advanced topics covered in it. Good book for a bit of theory, but I''d recommend the other book first.

Crystal space, and the nebula engines also have implementations of character animation you might want to look at. The nebula engine is slightly more advanced, and has some more easily understood code, though both work fairly well.

Milkshape3d is an easy to use animation program which has an easy to parse file format, and a bunch of free models on the net to test with. Check out cal3d for a bunch of file format/plugins for the various 3d programs.

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