Hey all,

I’m mucking around building an in-scene mantra lookdev hda. Basically it will frame up any geo in scene it's connected to and pull it into a lookdev setup. I’m stuck on one bit that someone might be able to guide me in the right direction.

I specifically would like to render multiple lightrigs, each to unique aovs from a singular mantra rop (which was easy enough) - but the trick is I want the light geo (ibl) to show in the aov as well. Normal per light aovs dont show the light.

I tried just rendering a Cf aov with a Light Mask filtering down to each lightrig but it didn’t work (and makes for a terrible Beauty pass). I’ve thought of adding sphere geo instead, mapping the ibl texture to match, however then would need to switch ibl textures per aov light render, or need to just be able to selectively render geo per lighting aov and not sure if that’s possible. This seems solvable if I had LPEs

Would be great to achieve a result without resorting to multiple rops or additional aov's to complete the pass. Would make for the best UX for the tool.

Thanks in advance!
Ollie

What role does the light geo play? Is it a camera ray stand-in for a geometry light/environment light, or is it actually contributing to indirect samples (Ce/emission)?

Using geometry lights/environment light is probably the only way to get separate contribution aovs for ibl at the moment.

If all you want is the camera ray geo to be correlated with the light rig aov, it should be possible to apply a shader to the ibl geo that exports the ibl as an aov. Then you can precomp it with the light rig aov.

Doing it all in one go probably would require LPE, or at least significant modification to the pathtracer shader.

Is there a reason to run each light rig in the same pass? The overbright nature of the beauty when running multiple light rigs will probably lead to over sampling if you are using importance sampling. However, I can see wanting to combine them if your asset is really heavy/has lots of displacement.

Hey jsmack,

Thanks for your response!

What role does the light geo play? Is it a camera ray stand-in for a geometry?

Basically yes. Using highres ibl's to have a background. I am using environment light with ibl + render light geometry ticked. Object does a spin then the ibl goes for a spin.

The experience I want the user to have is ability to switch aov and see each lightrig (with background render).

That said the hda has a per lightrig switch for the beauty while working (best for speed too) currently - and I guess I can make tab for then rendering outputs. I'm thinking I can use a separate aov and a COP net to create the final output all from the hda.

I think all I'd need is a single UV aov and remap each ibl map back on in comp - but I've never done that in sort of stuff in COP's - only Nuke. That would let me also provide blur bg option actually!

Does this sound feasible to do in COPs? Is there an equivalent to an STMap in Houdini?

Cheers,
Ollie

revilodesigns
Does this sound feasible to do in COPs? Is there an equivalent to an STMap in Houdini?

it's called Deform COP

Thank guys - Will get me going for a bit.

I've opted for a few more ROP's in the end, and will also make use of the Deform COP.

Cheers,
Ollie