I have some serious problems in my attached scene file. I have a shaft_emission which just creats particles in the initial state instead of generating fluid particles constantly, which is the normal behaviour.

As I extended the scene, there where no problems at all. For some reason something went wrong with the shaft_emission as I described.

Then I started trial and error for 2 days but did'nt get fixed it.

So I recreated the whole scene and it worked. The shaft_emission generates constantly fluid particles. After saving yersterday and opening it up today I have the same problem as in the beginning.

I have really no idea, if it is a bug or something else. Hope, someone of you can help me out

scene file (12.5.392).

Thanks

roughsporty
So I recreated the whole scene and it worked. The shaft_emission generates constantly fluid particles. After saving yersterday and opening it up today I have the same problem as in the beginning.

There is a problem with the Emitter_River that I believe is causing your problem, although I don't know offhand why it would suddenly work and then not work. To confirm this you can just disable that emitter temporarily and see if it fixes the problem.

A little background on FLIP emitters: A FLIP emitter generates both particles and a surface SDF, the latter being used to union with the existing surface SDF in FLIP. The SourceVolume DOP uses the surface SDF to cull any newly-emitted particles so that excess particles aren't added where the surface already exists (assuming Kill Inside is still on, which it is here.) In setups like yours with multiple, custom emitters, it's very important that each emitter create the proper SDF, since it's used to cull particles for any later emitters. An incorrect SDF can lead to particles from later emitters getting incorrectly culled, which I believe is happening here.

Your setup Emitter_River tries to ensure that the emitter tightly fits the carved-out part of the riverbank, using an SDF of the extruded riverbank for culling. This is correct for the particles, but not the surface SDF. You've got volumemix1 just copying over the riverbank SDF to use as the emitter's surface SDF, which isn't correct. This should be doing an SDF subtraction, so in this case you need to invert the riverbank SDF and Maximum it with the emitter, i.e. change the Source Pre-Mult to -1, and set the Mix Method to Maximum. The incorrect SDF was killing particles that came out of the Shaft_emitter, since it came later in the DOP Network.

Hi johner,

thank you for your help and the explanation of the flip background.

Disabling the Emittier_River fixes the problem so I made the the little changes and voila both emitters doing it's job :-)

At the end I didn't fully unterstand what you suggested but for now I'm quit happy that it works and I have to some deeper exercices about the flip thing.

Concerning the incorrect SDF … is the workflow right to mix them in the Emittier_River or should I prepar the SDF somewhere else or doing it without the volume_mix?

Thanks

Im having some issues with particles in Houdini Apprentice as well.

I Have created a FLIP Tank and a simple box emitter thati have then chosen to Emit particles from in the particle fluids tab. I have chosen the AutoDop Fliptank as my fluid and its created the particle network.

However when i play it back the particles are no emitted at a stream downwards but instead move and also get deleted when they try and emit from outside of the box emitter.

Anyone know how to fix this?

Hi there

It's a bit hard to understand what you're doing without seeing a hip file but if you are trying to emit particles into a tank of flip fluid via an emitter already covered by flip fluid that won't work. An emitter needs free space to emit into - a non technical description, sure there's a better way to explain that..

cheers
Nigel.