View Full Version : Linking rigid bodies to a skeleton

04-14-2005, 10:08 PM
I have a skeleton that is already animated with motion capture. I need to run a dynamics simulation of the skeleton crashing into a table full of objects. My plan was to create stand in geometry and parent it to the appropriate joints, then create rigid bodies out of them.

This doesn't seem to be working out. Does anyone have any ideas? The technique should either be something fairly painless to set up, since it will have to be setup many many times, or the technique should be scriptable, so I don't have to set it up each time.

Looking for any and all ideas here.

04-15-2005, 05:47 AM
hi mhovland,

well, if u already have all the animation on the bones, will they listen to any other motion inputs :shrug:? i mean, what u can try is, use the mocap data untill the charac flies on the table and just when it is about to crash in to the objects, the bones have to have thier rotations / translations free to be driven by the rigid body proxy objects..

i hope u have already seen this page >> Rag doll tut (http://www.goldenxp.com/tutorials/ragdoll/page1.htm)but just in case. Thought might be useful to u... according to this tut, the bones are completly in control of the rigid body proxy elements .. and that is how the rigid bodies react among themselves and drive the bones...giving the ragdoll effect...

maybe u can do a switch (similar to FK / IK switch) on ur bones by use of 2 rigs where one has the mocap data and then u have a switch attribute , when on, can make the core skeleton (to which the mesh is skinned ) listen to a "free" rig (which is controled by the rigid bodies) ... hope it is clear ...:)

cheers, :thumbsup:

04-15-2005, 03:49 PM
I think you misunderstood what I need. I don't want the skeleton controled by rigid bodies, I want the rigid bodies to follow the motion of the skeleton, and interact with other dynamic objects.

I want the simulation to look like the objects on the table and the table itself to react as the skelton (rigid bodies) come into contact with them.

I'm going to try to create a rigid body out of the actual geometry that is bound to the skeleton, but I'm not sure this will give me the results I'm looking for.

04-16-2005, 09:27 AM
hi mohvland,

oops ! soory.. but again.. yes, u can try making the proxy objects to be attached to ur bones , as passive bodies and make ur table and other items as active bodies.

this should work.. but i guess u have to playaround with the individual settings on the active bodies like the standin > u can use cube for boxy things or else set it to none (more slower) and try increasing the step size to .001 in ur solver.. it should give u pretty good results..

any idea of what the "Set Rigid body Interpenetration" option in the Solvers menu do ??


04-19-2005, 12:52 AM
I'm also trying to attach rigid bodies to my character. He is pinned beneath some heavy junk and is struggling to get free. My plan was to use proxy objects parented to the joints as passive rigid bodies and make the junk active. However, when I parent the passive bodies and animate the joint, the passive body assumes the position of the last keyframe at the start, so its geometry is actually offset from the joints. I tried using a parent constraint instead with "maintain offset" checked. It solved that problem, but the active bodies now react to the empty space where the passive body was before animating... I found a recommendation on here to use a nail contraint on the passive body and parent THAT to the joint... it works, except it the rotation doesn't translate, just the position... Any ideas???

04-19-2005, 02:59 PM
What I found to work is to make the proxy objects passive bodies, and make sure the transforms are frozen before creating the passive body.

This works in my situation, where I am using motion capture, it might not give you the results your after.

I would try doing the animation first, and then creating all the active/passive bodies and run a simulation.

04-19-2005, 09:25 PM
yup, I actually just figured out that was my problem... gotta do the animation before turning on the rigid bodies!

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