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Masoud

March 18, 2022 05:18:01

Hello guys,

In an RBD simulation, I would like to control the transform/rotation of the elements, to stop them from moving forever. The fractures travel too far away..!

I tried to use the "Drag" node, but it's hard to achieve the right value in its parameters!

So what's the best solution to fix it?

Actually, I want to achieve a falling behavior like what they made in this TVC:
https://www.youtube.com/watch?v=QbmW76Cp4s8 [www.youtube.com]

Thanks for helping.

mrCatfish

March 18, 2022 10:27:36

I would first try the bullet world scale parm... scale your sim up 100x. Bullet is notorious for rolling-forever small pieces. This causes the HDA to scale up your sim and all forces, then rescale it back down for you. This sometimes works.

If this doesn't work, then change your collision padding smaller. Often just making it 0 works fine. (Tiny pieces can be turned "inside out" by the collision padding.)

Still no joy? Then add a POP wrangle to first second input of solver to quickly ramp down angular velocity (w): (apologies if I stole this from someone on this forum):

// If speed and torque are less than a value reduce the torque
float spin = length(v@w);
float speed = length(v@v);

if(spin < ch("threshold") || speed < ch("speedthresh") ) {
    v@w *= 0.1;
}


// If the speed is less than .1
// stop the objects by making them inactive
if (@speed < .1 && @Frame > 1050) {
    @active = 0;
}

timjan

March 22, 2024 17:15:22

Just loved that answer, thanks!!