I know that in 2012, the most of you want simulations :), but still this is my old R&D on bones, muscle, skin animation which was created in Houdini 9.5/10 few years ago!
All work is mine. I dont use Houdini muscle and skin system.
Basic idea is based on settings bone poses and then define how muscles and skin(sliding) look in particular pose. This is much better than linking bones(muscles) with skin vertexes using weights. It has much more control, but GUI is not so user friendly :( currently. Also everything was done in houdini sop(obj) so I didnt use HDK(I havent known it, yet), so its very SLOW If you have more complex model. Muscles use a little bit jiggle effect(done i CHOP). Skin is projecting on muscles and original(non-raytrace) skin can change details(LOD). Also is really good to apply Smoth(Relax) SOP node if skin is too-muscular.
Blending among poses is based on Natural neighbor interpolation(en.wikipedia.org/wiki/Natural_neighbor), which uses voronoi tessellation.
This all is just R&D, so I will not release this tool, but MAYBE I will implement to Substitute. Anyway this was my first bigger project in Houdini and first larger practical use of my CG knowledge.
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