Phoenix particles not emitting from all geo of the source

[cam.crichton]

HI,

I have a simple smoke emission from a geo source (see image). The particles only emit from one spot of the geo (two sources are contained in the image, creating yellow and red particles in the preview).

Is there a way to control this, or force it to emit from the same area as the smoke - where the pink crosses are in the image?

Max 2019. Phoenix 4

[Svetlin.Nikolov]

Sure, you could map the outgoing velocity, smoke, particle, temperature, etc with a texture mask, you could also emit based on vertex color, or you could emit only from certain polygon id on the geometry - it's all in the Source option.

In case you mean that you want to emit from the entire geometry, but for some reason only parts of it do emit, I would suspect that some of the geometries interacting with the simulation are not watertight and this breaks the solver. The geometries must be clean, with no overlapping faces, no inverted normals, no missing faces. Open geometries such as planes are not okay since they don't have volume.

Hope this helps!

[cam.crichton]

Yes I meant the latter. I did not know that open planes were not OK. That's what I use 90% of the time. It doesn't seem to have any issue emitting smoke or temp from these planes - or do you mean the collision objects can't be planes? To make these dozens of objects watertight would take a long time and would be redundant if there were any model changes.

[cam.crichton]

I added a shell modifier to the collision objects - no change
I added a shell to the emitter - et voila, success!

[Svetlin.Nikolov]

Yay! This does apply to both emitters or obstacles, as long as they are solid, which requires them to have a volume, or if they emit in volume brush or volume inject mode. If the geometries are not okay, usually you can get away with it as the solver tries to work with what it has, but for fire smoke simulations you could start getting some parts of the simulation freezing, or if you also have moving geometries you could get explosions.

In short, it's a matter of luck to not have any visible issues, and shelling is the best and quickest solution if you run into weird behavior sooner or later

[cam.crichton]

thank you - I wondered after the fact though about surface force emissions - aren't they designed to work with a surface rather than a volume?

[Svetlin.Nikolov]

Yup, surface force just uses the normals, but usually Surface Force emitters are Solid as well and this makes the volume matter.

[cam.crichton]

I have a couple more issues with the particles...

Is there any way to control/limit the velocity of particles - or cull extreme velocities?

The preview menu for particles is not very functional, since you can't see the name of the particles but also it seems to be populated with an instance every time I simulate. You can see in the scene explorer there is only one particle object.

I am finding that the particles stop and start working each session. Yesterday they stopped working, I changed the mesh op in tyFlow from Vray to Triangle and they started working again. Then I switched it back to Vray and they kept working. Today they won't work on any setting (see inset of image 0 particles). I can't pinpoint whether this is a tyFlow or Phoenix issue.

[georgi.zhekov]

You could use the Particle Tuner and set it so that if a particle is moving too fast it will kill it or it would reduce it's speed.

The behavior you're getting seems strange though. Can you send over the scene so we can take a look?

Thanks!