Can anyone show me how to get good resources on this subject ?

Ragdoll physics is basically a simulation of constrained, articulating rigid bodies (body + limbs) with only gravitational and collision forces applied (no muscle forces or other internal forces).

The standard placed to start looking for ways to simulated constrained, articulating rigid bodies is David Baraff''s work. You can find many of his publications here:

http://www-2.cs.cmu.edu/~baraff/papers/index.html

I will warn you that this is not stuff for the novice physics programmer, and I believe there are some errors in some of David''s key publications. (Not entirely sure about that, as I''ve not tried to verify them myself. I just remember reading a comment somewhere from someone about that.) Of particular interest is his "Linear-time dynamics using Lagrange multipliers" paper.

If you look at the "Pictures" section of David''s site,

http://www-2.cs.cmu.edu/~baraff/pictures/index.html

you will see a "Lagrange-multipler tree and snowflakes". Don''t know if David makes available sample code for that thing, but its darn close to what you''d need for basic rag-doll physics. He''s constrained one body to hold the thing in the air, but other than that its exactly like rag-doll physics. (though he might not be doing collision stuff.)

Andrew Witkin''s work is also a place to look.

Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.