Hi, I have a little question about Houdini rigid bodies.

When i simulate (with RBD object) two objects that have the exact same geometry and scale but a different density in their physical tab, the two objects just fall down at the same speed. The one with a greater density should fall faster and it doesn't.

First i thought that my weight wasn't calculated at all. I changed the mass or the density, but nothing different happend.
Then i tryed to put thoose two same objects with a different density on the two sides of a simulated plank wich is on top of a tube. Like two weights on a balance and here, my density seems to work, the object with more density make the plank tip on his side.

My question is how do i add weight to a rbd object so that it falls faster.

I have linked an attachement, a hip where i have objects trapped in a container and the container has a MDD animation, my objects are simulated and their weight don't seems to be enought to make them stay inside that container.

Thanks in advance.

The acceleration due to gravity is independent of mass, so Houdini's behaviour is correct (from Newton's second law, F = m * a = m * g, so the mass cancels out). You could, for example, use a Drag Force DOP with Ignore Mass turned off, and that will slow down lighter objects more than heavier objects. I've attached an example of that.

Thanks, so the drag force, with ignore mass, will work as a kind of “air friction” ?