Is it possible to set velocity of the POP particles different per particle?
With expression like rand($ID) or to get the velocity value from the attribute?
Seems to be impossible but maybe I do something wrong?
Of course I can assign velocities individually with Velocity POP, but what about Location POP or Source POP?

Not quite sure I understand your question.

If you want to override/change the Velocity of each particle the Velocity POP is the POP to use, (or VEX). The Location and Source POPs are mainly generators, although they can set initial velocities based on the source geometry or some expression. If you have a Velocity POP after the Source POP the velocity should be override.

I'm talking about initial velocities of the Source POP and Location POP.

You can't use $ID and similar variables on the Generator POPs because those variables don't exist until after the POP is cooked.

If you want to set velocities on particles that were just created then you can make a group for all the particles birthed during the current timestep then limit the Velocity POP to just that Group.

Okay. It's impossible. The other one question is how to pickup the primitive attribute from sops in pops?
For example, I have a grid as the source for pop particles. That particles emit from primitive centers. So I can't pick the point attributes (???) and need the primitive attributes. Okay, I have the prim attributes. But how can I use them as parameter of Velocity POP? I don't see something like AttribPromote POP.

If you are emitting from Primitive Centers then you can use the origin attribute to determine which primitive the particle was birthed from. Then you can use the prim expression to query the attributes you need.

Hummm… I see nothing in your file :?
But anyway thanks for idea, it works

hoknamahn
Hummm… I see nothing in your file :?
But anyway thanks for idea, it works

The popnet is in /obj/model/popnet1

Glad it works.

The help card for the Attribute POP is really handy, it gives a list of all the common attributes/variables and which POP adds them.

hdox/houdini/content/helpcards/pop/attribute.xml