View Full Version : Making part of animated character a rigid body

04-01-2005, 06:53 PM
Ok... I'm having a rough time figuring this out.

I've got an animated character and the script I'm working on calls for him to begin to fall to pieces. I know how to do the dynamics part and I've got the character animated.

I cannot for the life of me figure out how to make a piece of the character get taken over by the dynamics solver while the remainder of the character continues to move.

Scenario - Arm falls to the ground dynamically. Character turns to watch his arm fall and bounce around, while responding to other things in the scene.

So, basically, i need to figure out how to have the dynamics take over at a specific frame (which could very well change, along with the actual animation), and disconnect the dynamic piece from its parent (the character) so that it is no longer controlled by the character movement.

Does that make sense? Can't figure it out. Argh!

thanks for any help everyone.

04-01-2005, 06:59 PM
I think I figured it out (that was fast).

Set Passive key - while character is being animated.

Set Active Key - when dynamics take over.

But, here's the tricky part... the object itself is never animated (say a piece of the character) - the piece that becomes dynamic never has any keys on it.

Will that cause a problem, or is maya smart enough to pull the transformation through the parent chain so that when dynamics take over, it will be transformed to where it should be?


04-01-2005, 07:46 PM
You could run the dynamics simulation on a piece of proxy geometry, and then animate a constraint to the proxy for the arm.

04-01-2005, 08:03 PM
Thx for the reply! That was my first thought actually, but since some things might end up changing, I didn't want to add any more levels of complexity than were already there.

I found that just using the active/passive keying of dynamic bodies, it works very well - including retention of any force before and after the dynamics are enabled (Soft and Rigid Bodies, Complex Motion and forces - Maya docs).

Only thing I need to figure out now is how to bake the simulation, disable the dynamic evaluation, and if things change, delete the baked keys and re-enabled the dynamic simulation (which I still can't figure out). Baking the keys speeds up playback immensely, but I don't know how to 'undo' that baking of keys.

Any ideas there?

04-02-2005, 01:06 PM
well, here's another possible approach that might help simplify things a lot -- use a couple of good camera cuts to produce your segment as a sequence of distinct scenes, each of which can be written as a separate scene file, dynamics in some, no dynamics in others. for example, scene1: character moving with normal keyframed hierarchical animation, no dynamics; scene 2: cut, arm falls off and bounces, dynamics; scene 3: character looks down at arm (or whatever), normal keyframed hierarchical animation, no dynamics; etc.

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04-02-2005, 01:06 PM
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