Hello everybody,

I am playing with the brand new MPM solver so I would like to ask the following questions:

a) if you create an object with different materials, let's say a buiscuit filled up with chocolate, how can you set up a set of constraints between the two materials?

b) I am testing collisions, a metal ball with a concrete slab and the as soon as the metal ball hits the slab, concrete particles stick up to the metal ball (which is not "normal" behaviour). Is there a way to control material stickiness?

Thank you.

MPM,like FLIP, works with a background grid that is not visible to the user by default. All materials are transferred to this background grid, so the contact between these two materials is going to behave like a blend between metal and concrete which is expected to be very sticky.

Reducing the particle separation on the mpmcontainer can help to reduce this effect. You can also reduce the gridscale from 2 to 1, to scale down the transfer stencil.

Another hack could be to do a first sim with both material simulated, then resim with one of the material as a deforming collider so you have full control over stickiness levels.

I talk about this issue/feature at 3:00:16 in the MPM Masterclass [www.sidefx.com].