Skybar

Definitely go for a wacom. I've exclusively used a wacom for houdini for a many years now and it's just wonderful, and it's a lot faster getting around and laying down nodes than with a mouse ontop of being ergonomic. If I only have a mouse I can barely get anything done and it's just tedious, I don't know how you people do it. Get a wacom.

Well what you get from a POP simulation is not a particle system. If you middle-click you can see that its just points basically. When you "Add Particle System" on those points you do get a primitive and an actual particle system, so the points will belong to this primitive. I think this particle system thing is a bit legacy from the old POP system before it was moved into DOPs, it's not really used for anything else that I know of.

Create a line, resample it and delete every second segment?

The geometry light doesnt need geometry per se, but it does need a primitive. So instead of copying geometry to the points, you can use Add SOP and turn on "Add Particle System" and geo light should work fine. The size and color can also be controlled per-particle with pscale and Cd which is useful too.

I dont know why, but if you pack the box before applying the material it works.

not sure what that refers to specifically but in vex it is i@group_foo = 1;

Cool good luck! Will you be running Houdini at all?

Put an Ends SOP before your polyframe and set 'close u' to "unroll", essentially converting your geo to a curve. Then put another Ends SOP after the polyframe and set 'close u' to "close" to close the polygon again.

Yeah, not sure about the technical terms but vex will only create geometry/modify attributes at the end of the code execution. vector thePos = point(0, "P", 0); // Input point's pos is {0,0,0} thePos += {1,2,3}; setpointattrib(0, "P", 0, thePos); thePos = point(0, "P", 0); printf("%d ", thePos); // Prints {0,0,0} instead of {1,2,3} Here you first set 'thePos' to the incoming P. You then add some values to it, and set P to be this new value. You then overwrite 'thePos' with the incoming P again, mind you the code execution isn't done yet so this will still be the original position.

In H16 it is CTRL+I or go to Tools -> Edit Background Images.

Not sure what you mean, Particle Fluid Surface uses VDBs internally. You can choose to output VDBs from the Particle Fluid Surface and combine them afterwards if you'd like.

The stacking up thing? I suppose the easiest would just be merging the maximum of the volumes post-sim per frame.

Could always send an RFE to sidefx if its something you want.

It looks like your collision velocities are the problem. New particles in the front immediately collides and gets pushed forward with that velocity. You can test this by setting Volume Motion -> Velocity Scale to zero and it should only collide and flow along, ignoring the collision velocity.

Yeah why not, try it. edit: I mean if you want different materials like that you probably have to do it another way.. But just different textures with different uvs it should be fine. Maybe need some way to mask between them though if they're overlapping. Sorry maybe I was too fast to answer