Dust Effect

[lexlopez26]

Hello! I'm working on putting dust on the tires of a car as it speeds. This is probably the dumbest question but, what precisely do you control the direction of the smoke effect? I don't want it to go up, I want it to be static until a collision happens. 

 Please help,

-Alex

[Yon]

Anything that works on the velocity field, buoyancy lift/direction parameters are basic.

Try using the tires as a source to a particle network and set Emission Attribute to v.

In SOPS, use a trail sop to set to compute velocity, then wrangle this;

float emit = ch("Threshold");
if(@v < emit) {
@v = 0;
}

Particle will only spawn when greater then the Threshold parameter, and emit more the faster they spin. Then source your dust from these particles.

 

[catchyid]

Just out of curiosity James, how would you use these particles to create the look of dust? I think using these particles as a source of smoke + smoke solver would work? 

Thanks,

[Yon]

Yeah just using the pyro/smoke solver. If anyone hasn't sourced from particles you can run shelf tools off them in your import_particles node. I haven't tested that particle setup but it works in theory. Then it's just dialing parameters and using a low density shader.

[lexlopez26]

Thanks James!! It worked!!

One other question if you don't mind, have you ever emitted particles from an animated Alembic file?

[Yon]

No but it shouldn't be any different. If the abc archive node is throwing you off you can always write it out as bgeo.sc and bring it back in.

[rbowden]

Shouldn't even have to write it out as a bgeo.sc unless you are manipulating the geo itself and getting rid of groups and attributes. Since alembics come in as packed geo, you just need to put a convert sop or either an unpack sop after your alembic so you turn it into polys. After that you should be good to go.