I made a large box emitter and let some Marbles ran over it.
But how could I have some interaction with the smoke and marbles?
You know if marble is rolling over the smoke emitter, there should be an empty trail behind the marble for a few seconds - until the smoke start to rise again… This is what I am after now.
See the Collision section in the documentation Wendy linked. Collision support is limited today. It requires recycling of emitters with special configuration. For a bunch of instances of spheres like this, should be feasible though using sphere emitters. My recollection was this was done for the original Marbles demo.
On FlowSimulate, there is now a ‘Physics Collision Enabled’ option. This will bring PhysX convex hulls into Flow. This can save a lot of time over doing manual collision setup, but do note today performance overhead can become significant for scenes with many PhysX colliders.
Towards the end of the video, you scroll down to where it shows the collision approximation as Triangle Mesh. You have to switch this to convex hull or convex decomposition to work in this case.
Even then, plane like that might end up making very thin convexes. So if that doesn’t work, do try a thin box with convex collision.