I have 2 streams of particles in a dopnet, now i'm adding a popwrangle to control just one of them, so in the Inputs tab -> Input 1 - I select DOP Data.

But what do I type there ?

Docs say: “Data in the current simulation to reference. Specified as an object/data, for example, pyro1/vel to refer to the velocity field of the pyro1 object (which will show up as three volume primitives).”

So I try:

popobject1/stream_popsource_02

or

popobject1/Geometry/stream_popsource_02


and no-go. stream_popsource_02 is the stream I need to sample from.


Also, please, someone state where in the docs I'd find the info needed to solve this.

To me it seems frustrating to rely on the good will of fellow users in the forum for something I should be able to find out by myself.

streams are just groups and groups are subset of geometry
so if you want to access just other stream of current geo you still need to point to “myself”
or if it's stream of another object's geometry then you would use DOP Data nad something like: popobject2/Geometry

then depends on what functions you use to sample them, many sampling functions have group argument where you put the stream name

to the docs question:
the info is there, but it's kind of scattered and then all the knowledge comes together and it will all be clear, however you will not find every possible workflow step by step in there

- so for your case you need to know that streams are just groups of the same pop objec geometry: http://www.sidefx.com/docs/houdini14.0/dopparticles/streams [sidefx.com]
- that same functions can take group as an argument therefore you can use them directly on current geo, example function: http://www.sidefx.com/docs/houdini14.0/vex/functions/pcfind [sidefx.com]
- or that you can use SOP Solver DOP to execute SOP network on your particles
https://www.sidefx.com/docs/houdini14.0/nodes/dop/sopsolver [sidefx.com]
therefore you can just split off one stream (Split SOP, Blast SOP, …) therefore get temporary geo containing only particles of that stream and sample that directly within the same Solver SOP to modify particles and return, etc.

but there is nothing wrong with asking on the forums, you can actually learn faster that way, once when things start to make more sense you will feel more comfortable exploring on your own just intuitively using correct data in correct way

Thanks ! It works. Well, I kinda figured every possible workflow is not listed in the docs, but I've spent/wasted countless hours reading and studying the help files and the knowledge I get is very little relative to the time I invest, specially when I compare it to the knowledge and well spent time I invested 10-15 years ago learning maya. Its help is( was? I haven't looked at it in a long while ) well structured and very very easy to follow, I could read it from top to bottom and everything fell into place.

I've been trying to learn Houdini since version 8, and only 2 years ago I had enough time and dedication to break through, thanks to a couple cmivfx tutorials.

Anyway I feel I'm almost there to finally get a good grasp of the app, but thanks to you and other sources, not the documentation where it should be.

I still hope sesi would fix it on behalf of others struggling, I know how it feels.

Thanks Tomas.