bunker

yeah I've seen this tutorial, not bad I'm hoping to record part2 soon, I've been a bit busy with work and the whole "end of the world" thing going on right now...

@doc you don't need substeps if your source is already motionblurred trail_pyro_source_bunker_001.hipnc

not sure what you're doing with the modify data DOP, it's just a like setting a value on an attribute, it really depends what you do with it.

sorry I though you wanted the impacts points but you want the actual records, a bit different. you'll see the impacts in DOPs under DopObject/Impacts but only on the frames where you get impacts:

put down a Sopsolver inside DOPs, everything is ready on the "impacts" node.

you could use VOPs if you don't like code https://www.sidefx.com/docs/houdini/nodes/vop/unifiednoise.html for a box-like pattern, have a look inside the gasDisturb DOP node

here is a simple solution without any solver tweaks: - create a random int attribute per point and convert it to float: f@r=int(rand(@ptnum)*1000); eg: r = 153.0 - on the FLIP solver/reseeding/interpolate attributes, add the attribute r - as a post sim process, you can compare the original attributes and interpolated ones, they will have a decimal value >0 eg: r = 154.462 if(f@r-int(f@r)>0)@Cd={1,0,0}; in practice, this isn't 100% perfect so you can use a vector attribute instead, have a look at the attached HIP separate_reseeded_bunker_001.hipnc

have a search on Odforce and the SideFX forum, there are tons of posts...

Nothing weird there. Your sphere doesn't have normals, @N is creating them on the fly. Have a look at your Geometry spreadsheet.

I had a look at your hip file now actually, you should put that wrangle after your "volumesource2", just plug it there in the latst input of "/obj/pyro_upres/upres/merge2"

Upres doesn't compute any velocity (and collisions affects vel obviously) so you won't get exact collisions. the lowres vel field is upscaled and curl noise is added so some density might (will) enter the collision field. You can add a gasFieldWrangle as the last stage of the solver, or anywhere you want, it's removing density inside the collision on every frame. hope that makes sense.

have a look at the hip file on page 2:

Here is my tutorial, done super fast so don't be too harsh I hope this is helpful Sparse Pyro Upres, the easy way - part1

https://pybullet.org/Bullet/phpBB3/viewtopic.php?t=10783