[ODE] matching oriention/position

[Manu Beau]

Hi everybody,

i have got a problem which seems to be easy to solve
but all my tries has failed. 
My problem is the following one : i have a character
animation (walk, jump, etc.) and i want to create a
rigid body (RB) which match head's position and
rotation (keep the rigid body in the air). On top of
that, i have some RB linked to this one like a hair
cut (woman's plait, etc.).
The goal of this simulation is to propagate head's
movements to the RB linked to it in order to obtain
realistic hairs moves. Thus, the RB which represents
the head must reproduced head's dynamics (i.e. its
translation and rotation).

Notice:
the head RB is the root of all hair cut RB.

My first naive solution was to set head's position and
orientation from animation data at the beginning of
each frame (I know, this is not a good physics
simulation :)). The results of this simulation are
very bad ... as expected :).

I intended to construct a physics model thanks to
various type of joints on the RB which represents the
head but they are some "collisions" between rotation
and translation constraints.

I tried to break down the problem in two different
simulations (one for each issue):
- match head's translation:
At the beginning of each frame, i create a slider
joint  between the head RB and the world. I set its
axis in the direction of the head's movement. On top
of that, i use some motor parameters (Fmax, velocity
and cfm) to reach the desired position. At the end of
the frame, i destroy this joint.

- match head's rotation:
This simulation is very similar. At the beginning of
each frame, i create a hinge joint between the head RB
and the world. Joint's axis is set to head's rotation
axis. Beside, i use some motor parameters (Fmax,
velocity and cfm) to reach the desired orientation. At
the end of the frame, i destroy this joint.

Notice:
Head's rotation and translation are deduced from the
last and current animation frame.

These two simulations work well separately but i don't
know how to put them together and build a unique
physics model.

I don't know if this is the good way ... please help
me :)

If someone has an idea to simulate head's dynamics or
knows a thread which treats a similar problem, do not
hesitate.

Manu Beau.



	

	
		
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