Help Smaller emitter scale and particles

[krolu]

Hello, I've got a problem with Obi Fluid, especially with emitting a tiny track of fluid.

Main problem is that I can't set emitter radius as small as I'd like to. When I reset all scripts or add new emitter, solver etc., it works perfectly fine.

But ... when I start decreasing radius of Emitter Shape Disk, it starts to throw particles around or particles become invisible. I also tried to change params as resolution in ObiEmitterMaterial or Radius Scale in Obi Particle Renderer. Even rescaling emmiter by transform didn't work well. 

I noticed that by changing value in params I mentioned before, spourt of fluid becomes drops which are emitted separately.

Any idea how to create tiny track of fluid ? Thank you, in advance, for answer.

[josemendez]

Hello, I've got a problem with Obi Fluid, especially with emitting a tiny track of fluid.

Main problem is that I can't set emitter radius as small as I'd like to. When I reset all scripts or add new emitter, solver etc., it works perfectly fine.

But ... when I start decreasing radius of Emitter Shape Disk, it starts to throw particles around or particles become invisible. I also tried to change params as resolution in ObiEmitterMaterial or Radius Scale in Obi Particle Renderer. Even rescaling emmiter by transform didn't work well. 

I noticed that by changing value in params I mentioned before, spourt of fluid becomes drops which are emitted separately.

Any idea how to create tiny track of fluid ? Thank you, in advance, for answer.

Hi there,

Decreasing the radius of the emitter disk won't affect the size of your particles, only the size of the emitter. Neither will changing the radius scale in the particle renderer, quote from the manual:

Changing the radius scale does not affect the actual physical size of your actor's particles. It just draws them bigger or smaller than they really are. They will still use their real radii when involved in collisions, fluid interaction, etc.

To change the size of the fluid particles, either increase the fluid material's resolution, or use local-space simulation and scale the solver down. See:
http://obi.virtualmethodstudio.com/tutor...rials.html
http://obi.virtualmethodstudio.com/tutor...space.html

[krolu]

Thank you for reply ! Reducing the particles resolution still does not solve my problem ... Particles do not behave like liquid but like drops that drop eg. from a tap (there is offset between spawned particles). Also, when you reduce the resolution of the particles, all or most of them are made in the same time (depending on their defined amount), which create small lags on scene. I tried to reduce the emitter and particles, but they began to become less visible or disappeared or all begin to fly in different directions. Is there a limit of reduction of particles that defines the correctness of their functioning?

[josemendez]

Thank you for reply ! Reducing the particles resolution still does not solve my problem ... Particles do not behave like liquid but like drops that drop eg. from a tap (there is offset between spawned particles). Also, when you reduce the resolution of the particles, all or most of them are made in the same time (depending on their defined amount), which create small lags on scene. I tried to reduce the emitter and particles, but they began to become less visible or disappeared or all begin to fly in different directions. Is there a limit of reduction of particles that defines the correctness of their functioning?

Hi there,

There's no upper or lower limit to the size of particles, however, remember that in computer simulations time is a discrete quantity, not a continuous one. This means that if you're emitting very small particles at high enough speed, a whole timestep has to pass between each opportunity to emit particles. For particles large/slow enough this is not an issue, because the particles emitted don't get a change to move far enough from the emitter's surface before the next batch is emitted. However, if they are small and/or fast, they will get too far away in a single timestep, so a gap appears between emissions.

The only fix for this is to decrease Unity's fixed timestep. This however increases the cost of the simulation, as more timesteps must be taken per frame.

kind regards,