Ragdoll constraint - relative influence of the objects

Ragdoll constraint - relative influence of the objects

Hi, I'm currently working on reproducing the physics based one-legged hopper made by Russel Smith (same guy who made the ODE physics engine), you can see some examples here http://q12.org/phd-movies.html , the top three videos.

This hopper consist of a big, wide cylinder (called "body") of mass 6.0 and a thin leg under it which consists of 3 cylinder parts, a total of 1.5 mass - and then a ragdoll-joint/constraint between the bottom of the body and the upper part of the leg. All bodyparts have the motion type MOTION_DYNAMIC, so they are not fixed to the world.
What I want it to do, is to use the ragdoll joint to rotate the leg while the hopper jumps and is in the air, but right now mostly the body is rotated when I want it to be the leg that is rotated. How can I change the relative influence of the ragdoll joint so that mostly the leg is rotated when changing the target relative orientation? Increasing the weight of the body does not seem to help at all.


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Hi Joel,

There are a few things you can try to get the behavior you want. One would be to increase the inertia tensor for the body, making it more difficult to rotate. Another would be to adjust the center of mass for the body to be closer to (or directly on) the ragdoll joint. This should reduce the torque you are applying to the body. Those are the first things I would try.


Josh S. Havok Developer Support Engineer www.havok.com

Followed your tip and calculated the inertia tensor using a volume that is several times larger than the actual volume, and got the behaviour I wanted. Thanks Josh :)

EDIT: wording

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