Deforming meshes not fully supported?

[rachels]

If I have a fire/smoke sim, and try to use a deforming mesh as a smoke emitter, the smoke will emit from the properly deformed surface of the mesh, but the mesh itself will not contribute to the velocity of the grid. Like, at all. No matter what I try. So the smoke won't collide or move based on the motion of the deforming mesh.

If the mesh doesn't deform and is animated with its transform, velocities work fine.

I'm using Phoenix 3.03.00. Is there a plan to add this feature at some point? Seems like a glaring oversight to not have it already.....or maybe I'm doing something wrong? "Animated vertices" is turned on in my object settings, and the object is added to the sim, object velocity multiplier set to 1.0, etc. Still, it has no velocity influence on the grid.

[Svetlin.Nikolov]

Hey, is the mesh Non-Solid? If it's Solid, it would contribute velocity by default, otherwise you need to plug it into a source and have the Motion Vel. in the source enabled

[rachels]

Thank you Svetlin,

My object is indeed not set to solid. However, even adding it to a source and turning on "Motion Vel" (and setting it to 1) does not result in it contributing any velocities to the grid. This is true whether emit mode is set to surface force or brush. I am able to repeat this issue using a simple scene with a sphere that emits some smoke and a box (skinned to a single bone) that deforms through the smoke, so it doesn't seem to be an issue related to my more complex character setup, but instead all deforming objects in general.

If I set the deforming object to "solid", I can see its velocity influence on the grid again, however it doesn't seem to be colliding with the smoke in the grid. If I take the above setup (a sphere emitting smoke and a box moving through it) and convert the box to a static mesh and instead animate its transform, the smoke collides with it nicely and is pushed around by it. This effect does not occur if the object deforms instead of transforms. Is this a known limitation?

[Svetlin.Nikolov]

Not really a known limitation, no. We do have test scenes that check similar scenarios, so it must be something particular that's causing it to act unexpectedly. Would it be possible to attach a scene or scenes that have such issues?

Thanks!

[rachels]

Here's a quick video and 3dsmax 2017 scene file packed into a .zip showing the issue I'm experiencing. You can see the deforming box set to solid is affecting velocities, but not colliding with the smoke. You can also see the deforming box set to non-solid with a phoenix source that has motion vel turned on is barely affecting the grid at all. The translating non-deforming box works as expected.

[Svetlin.Nikolov]

Hey, thanks very much for the scene!

With 3.04 the 1st and 3rd simulator now behave the same way, so it's no longer an issue with deforming versus regular geometries - there was a fix for that issue a couple of weeks back which was originally found in Maya, and this was fixed in Max as well.

There is indeed an issue with non-solid deformable non-solid bodies not being able to contribute velocity to the simulation in Max! The fix for this will be in tomorrow's nightly.

Thanks again, cheers!

[rachels]

That's great news! Thank you!