magneto Posted October 1, 2015 Share Posted October 1, 2015 Hi, I am just trying to use the Gas Diffuse DOP to diffuse point colors in a FLIP sim as an exercise but Houdini complains not having pscale, mass and/or density on the particles. I added the first 2 but still the same result. I opened the original file from SESI where this was shown, but it complains about the same problems in H14. How can I make this microsolver work with a FLIP solver to mix colors? I normally use volumes for this but I want to learn about this microsolver, unless it's obsolete. Thanks 14.Diffuse.hip Quote Link to comment Share on other sites More sharing options...
Skybar Posted October 1, 2015 Share Posted October 1, 2015 Did you read the helpcard? If diffusing a point attribute it is important that the density attribute be already properly set by the Gas SPH Density node. This is done in the normal particlefluid solver, but if the diffuse occurs after some emitters, the newly emitted particles will not have a proper density value, introducing NANs into the system. FLIP doesn't have the density attribute so it won't work straight on the particles. However you can do something like this, faster to work on volumes anyway: flip_diffusecolor_dv.hipnc 1 Quote Link to comment Share on other sites More sharing options...
magneto Posted October 1, 2015 Author Share Posted October 1, 2015 Thanks Skybar. I did but when I tried Gas SPH I got the density warning on that too. Gas SPH Density only asks for Geometry so not sure what else I have to do? Your technique is nice, but is it possible to do this purely on particles without creating fields? Because that's what I wanted to try with the Gas Diffuse as it seems to support both. Quote Link to comment Share on other sites More sharing options...
anim Posted October 1, 2015 Share Posted October 1, 2015 it is, but you may not want to do that it's there from SPH workflow, which is very specific about attributes as well as them being correct, so density represent pointcloud density as opposed to fluid density as in FLIP, etc. you need as well to compute neighbor list for that and all in all, just to get SPH stuff to work, you will get so much slower sim that it's not worth over volume sampling but if you are curious, just have a look into Particle Fluid Solver and Particle Fluid Object for attribs and nodes needed for Gas SPH Density to work overall I can imagine that Gas Diffuse on points is using pointcloud filtering using some smoothing kernel, which you can easily do in VEX or Attrib Transfer, however it will be slower than volume method 1 Quote Link to comment Share on other sites More sharing options...
magneto Posted October 1, 2015 Author Share Posted October 1, 2015 Thanks anim, that makes a lot of sense. Are these nodes still useful nowadays or are they obsolete? If they are obsolete, it would be nice if SESI hid them. It creates a lot of confusion. Quote Link to comment Share on other sites More sharing options...
Skybar Posted October 1, 2015 Share Posted October 1, 2015 I wouldnt say Gas Diffuse is obsolete. Maybe the geometry part of it is, but its still useful for volumes imo. 1 Quote Link to comment Share on other sites More sharing options...
anim Posted October 1, 2015 Share Posted October 1, 2015 well, the Particle Fluid Object/Solver are still there and possibly can be used, so I wouldn't say obsolete, it's just specific 1 Quote Link to comment Share on other sites More sharing options...
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