Ray SOP against geometry from an instance node?

[Kardonn]

Working on some layouts here and was hoping there's some not-too-messy way of getting at the instanced geo being generated by a geometry node that's doing fast point instancing of some other objects. In this specific case I want to sprinkle snow on a bunch of things I've scattered, but I've run out of ideas on nice ways to get access to that geometry other than reproducing my instance setup somewhere else as a Copy SOP setup.

Just wanted to double check that's pretty much my only course of action here before I get started on doing it.

Edit: Potentially have a funny idea of a workaround using the GI Light to generate photons that I'd just use as my points.

Edited November 1, 2016 by Kardonn

[galagast]

The workaround sounds neat! It reminded me of something I did back then, where instead I used the point world position + normals of a rendered static image, and loaded it back to the scene as point clouds. The normals where then used to just detect points facing upwards for meshing (snow cover).

Maybe you could store a bunch of pre-scattered-point sets that corresponds to each of your geometry instance. Then have an id attribute to match those back. Just make sure you also have normals on those pre-scattered points for isolating normals facing up. But yeah, I guess that could also get a bit messy depending on the scene >_<

I would also love to hear about any other workaround for this

[petz]

On 1.11.2016 at 6:07 AM, Kardonn said:

Working on some layouts here and was hoping there's some not-too-messy way of getting at the instanced geo being generated by a geometry node that's doing fast point instancing of some other objects. In this specific case I want to sprinkle snow on a bunch of things I've scattered, but I've run out of ideas on nice ways to get access to that geometry other than reproducing my instance setup somewhere else as a Copy SOP setup.

Just wanted to double check that's pretty much my only course of action here before I get started on doing it.

Edit: Potentially have a funny idea of a workaround using the GI Light to generate photons that I'd just use as my points.

take a look at the linked thread below. it´s a bit old but somewhat similar to your problem and the uploaded file might be still useful ...

forums.odforce.net/topic/10418-how-to-emit-particles-from-a-displaced-surface

 

hth.

petz