ive got a deforming alembic object that i wish to collide with a grain sim.

ive tried both the “ray-intersect” based “static object” (with deforming mesh enabled) and vdb based “deforming object” methods.

the vdb based option is much,much faster, even with the voxel size turned down so the collision is (seemingly) very precise.

so obviously id like to use this method.


however, the results are terrible compared to the ray-intersect based setup.

im colliding with a grain sim, and i get very strange grain behaviour around the collision object when using the vdb method.

it looks ok initially, although my collider (growing from below the sand) doesnt seem to lift as much sand up when using vdb,

but later on in the sim, once the object has grown through the sand layer, and the “stem” passing through the sand is more or less static ( its still moving vertically a bit and twisting slightly, but is a smooth cylinder at this point)

with vdb i get a huge gap around the collider with the particles swirling around it.

note this is with a very precise vdb representation.

with ray-intersect based collisions i do not get this effect.

any way to get sensible grain collisions with VDB of a deforming alembic?