RBD simulation: I need to stop objects bouncing!

[Masoud]

Hi guys,

In my RBD packed objects simulation, some of the falling objects never stop bouncing and jittering.

How can stop them?

 

Thanks for helping.

Diamonds_01.hip

[Atom]

I just cross fade them with a final frame near the end of the animation. Drop down a TimeShift node and pick your frame, then shape blend into that frame.

[kushaldas]

In my experience, bullet has a really hard time handling small concave geometry. With your diamond geo, you can get a pretty close shape to your input geo with a Convex Hull representation and a reduced Collision Padding. To really have it settle in sim, you can combine that with a simple wrangle to slow down the pieces and mult down their angular velocity once they are below a certain speed. Atom's trick is great as a post sim solve, if you don't want to change the dynamics of your sim too much. 

Diamonds_02.hip

[paranoidx]

Your small diamonds have a complex shape. But in this case, instead of using a concave shape, it's better to use a diamond convex hull - still posible. This can be done by decreasing the collision padding of the convex hull. We have power performance better.

Image

 When working with physics in Houdini, it's a good idea to review the physics of your objects first. Ensuring that collisions are accurately simulated can make your work less stressful. Before making any changes, take a look at real video footage of how diamonds bounce and spin. Considering that 70 frames is a short time for such material, it's interesting to think about what kind of material could stop spinning in just 2 seconds from almost a meter away – just a little joke on my end.

For the RBD Packed Object physical settings:

• Lower rotation stiffness to prevent excessive rolling and spinning around an axis (the main issue causing the spinning).
• Decrease bounce to a very low value, although this may not be realistic for a real diamond.
• Increase friction to help slow down the object's movement.

For the Ground Plane Collision physical settings:

• Further reduce bounce to 0.0015 to minimize bouncing off the ground when interacting with objects.
• Set Bounce Forward to 0 to prevent any forward motion from bouncing.
• Increase friction, but be cautious not to overdo it as too much friction can make the diamonds feel like organic rice falling.

In some cases, I may add a pre-roll, but in this instance of falling in 70 frames. That's why my solution involves adjusting it for the 70-frame duration, but for me, this type of material without any bounce more and jiggle after 70 frames, so weird.

Edited May 31 by paranoidx

[Masoud]

Thank you guys