Sand Simulation

[TimLG]

Hi!

I'm a student at NAD in Montreal and I'm trying to learn Houdini.

I have a project in which I need to simulate sand on top of a falling rocks RBD simulation, which is on top of a FEM sim. (The FEM is the deforming ground)

So I cached every collision objects with the CollisionSource node (with 4 substeps to match de grain solver).

Now, if I simulate the sand, it explode on random frames. (see flipbook here: password: sandsim

This is my second attempt and it still explode (at fist I used 10 substeps)

 

Does somebody have any ideas on what could be the issue?

 

Thanks 

MountainGrowth_47.hipnc

[TimLG]

After some tests, the problem comes from the animated rocks. Even without animation on the rocks, the sand explode.

In my DOP, I load only 1 cached VDB of all the rocks as a collision object.

I tried to switch from a POP Solver to a FLIP Solver just to see the CollisionGuide of the rocks (how the solver see the rocks) . And it seems fine.

 

Any ideas?

[Atom]

Try dropping down a velocity damping node after gravity. You might be able to tame it down to a reasonable look.

[TimLG]

I can't find the velocity damping node, but I'm going to try with a POP Drag node.

 

Result:

It's better, but I can still feel the pop!

Edited November 22, 2017 by TimLG

[TimLG]

View from an other angle.

There's no interpenetration on the first frame

 

Password: sandsim

 

Edited November 22, 2017 by TimLG

[TimLG]

Ok, so now I know that

-It's working with static and not cached rocks

-It's NOT working with animated and not cached rocks

-It's NOT working with cached rocks, animated or not

(all tests with no substep)

 

Now I think that I may need to send to the DOP Network my 800 rocks separately... but how?