I'm messing around with the creep pop and I have particles moving across a deforming surface and those particles are emitting new particles that I wish to stick to the deforming surface where they are born.

I was thinking I might beable to through an expression in the Prim U/V section of the creep node for the trails but I can't figure out out to get UV coordinates of the parent emitting particle and pass it to the new particle..

any thoughts?

xyzdist() expression can help
http://www.sidefx.com/docs/houdini10.0/expressions/xyzdist [sidefx.com]

it can return you nearest primitive number to the specified point
as well as it's u and v parameters
pretty much everything you need for creep pop

tamte
xyzdist() expression can help
http://www.sidefx.com/docs/houdini10.0/expressions/xyzdist [sidefx.com]

it can return you nearest primitive number to the specified point
as well as it's u and v parameters
pretty much everything you need for creep pop

okay that looks good.. I'm not really sure how I'd use it..

so if I put this command into the Prim U/V parameters of the trailing creep it'll grab the birth position?

Swissarmychainsaw
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so if I put this command into the Prim U/V parameters of the trailing creep it'll grab the birth position?
…

no

it will find the closest surface of the geometry and it's info

so basically
you have deforming geometry
you have particle creeping along it
the particle is leaving other particles behind
so we can assume that the newly born trail particle is more or less somewhere on the deforming geometry
so if you take that particle (only for the monment it is born) and use xyzdist() to compare its position to the deforming geometry you will get primitive number, as well as u an v parameters of the closest location of the geometry to the particle position
so if you put this info to the particle through new creep pop or attribcreate the particle should stay sticked on the geometry

tamte
so if you take that particle (only for the monment it is born) and use xyzdist() to compare its position to the deforming geometry you will get primitive number, as well as u an v parameters of the closest location of the geometry to the particle position
so if you put this info to the particle through new creep pop or attribcreate the particle should stay sticked on the geometry

Okay I understand the concept but I'm struggling to understand how to actually implement this. I don't know how to execute a command when the particle is born.

I've attached the scene file I'm working with, part_trail creates the “trail”.

actually it is easier than i thought
just add creep POP to your source POP in part_trail network
and that's it

since the master particle is sliding along the surface, it has all the attributes needed (pospath, posprim, posuv)
and since the trail particles inherit them, they can use them, they just need pstate attribute set to stick which will be set up by the creep POP

tamte
actually it is easier than i thought
just add creep POP to your source POP in part_trail network
and that's it

sick.. I swear I thought that was the first thing I tried.. that's so much easier/faster than doing the same thing in Maya.

Although I am still interested in knowing how you'd execute a command at a particles birth

Swissarmychainsaw
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Although I am still interested in knowing how you'd execute a command at a particles birth
…

just specify the birth group in source(or split) pop
make sure Preserve Group is unchecked

this way the newly born particles will be in that group, but only for the moment they are born

so use this group as a Source Group for creep POP or whatever pop you want to modify only the newly born particles