Light select with SSS material does not match lighting pass

[sharktacos]

The light select pass (when set to "diffuse") should be the same as a lighting pass for the selected light(s). However it instead also includes SSS info in the pass. This means it is not possible to recreate the beauty when using light selects.

As a work around I tried this in comp:
LightSelect - SSS, clamp

+ SSS + specular = beauty
This get's close but does not quite match

I wanted to check into see if this was on your "to do" list for future updates?

thanks!

[Svetlozar Draganov]

Yes, we have that issue into our bug-tracking system but is is not fixed yet.
We'll keep you posted.

[sharktacos]

Wondering if this will be fixed for SP1 (Vray 3.1)?

[ivaylo.ivanov]

No, it's not fixed yet.

[sharktacos]

No, it's not fixed yet.

Bummer. Once it is, what would be ideal is to have a new drop-down menu option for SSS. So the choices are normal, raw, diffuse, spec, and SSS.

[tashko.zashev]

Bummer. Once it is, what would be ideal is to have a new drop-down menu option for SSS. So the choices are normal, raw, diffuse, spec, and SSS.

Yes, that would be a good upgrade when the main issue is fixed. We will keep you posted.

[joconnell]

I got this on the max side, the fix was to render the light select in diffuse mode and use the diffuse filter to divide it to make a new raw - you'll get the sss bits in there. Admittedly it's not perfect since the result is sss + whatever diffuse was also in the material but it might be good enough for you in this case.

[jasonhuang1115]

I got this on the max side, the fix was to render the light select in diffuse mode and use the diffuse filter to divide it to make a new raw - you'll get the sss bits in there. Admittedly it's not perfect since the result is sss + whatever diffuse was also in the material but it might be good enough for you in this case.

Good tip, John. Hope this trick works on Maya side as well. Will need to test it out. Does this trick work when there are multiple Light Select AOVs? Were you able to put together a matching comp result to the beauty?

[joconnell]

Yep - what happened was the raw didn't contain the sss data but the diffuse did so making my own raw via the diffuse filter made something that recombined directly. It helped quite a bit with the 2 sided material too, that had some weird tints on edge pixels on a load of trees so making your own raw light was nicer.

Likewise I think the raw lighting and GI didn't perfectly match on the sss so sss / diffuse filter gave us a useful raw light here too.

[jasonhuang1115]

Cool. Thanks again John. I need to play with this in Nuke to learn.

[jasonhuang1115]

By the way John, are we able to pull a similar trick to isolate the GI from each light select? If yes, we pretty much can achieve what Maxwell can do with its MultiLight feature to re-build the beauty completely, though in more complex fashion in post...

[joconnell]

Light select is the direct light only unfortunately, currently GI can't give you the gi for a particular light either, it's a shared pass so there's no way to do exactly what you say.

[jasonhuang1115]

I see. Thanks for the clarifications. Talked to Vlado before about this and believed we will get there (isolate GI contribution on per-light basis) one day.

[joconnell]

Yeah - I think it's handier to do the more we use brute force / per pixel methods rather than irmap.

[sharktacos]

I got this on the max side, the fix was to render the light select in diffuse mode and use the diffuse filter to divide it to make a new raw - you'll get the sss bits in there. Admittedly it's not perfect since the result is sss + whatever diffuse was also in the material but it might be good enough for you in this case.

When you say "diffuse filter" do you mean the diffuse RE?
Lighting / diffuse = raw light