LPE for Specular Reflection including the Reflection of the Shadow

[sschierwater]

As the title says, we are trying to write an LPE which renders a Specular Reflection that includes the Matte Shadow from a shadow catcher, on top of the LightDome texture.. We can acheive this with the default Render Elements, but that unfortunately includes the flakes of our car paint shader, and we would like to isolate just the Specular Reflection.

this is what we are currently using, but the reflection of the shadow catcher is all black.

C<RS>.*L

Cheers!

[hermit.crab]

Sorry to say, matte reflections and gi, currently, cannot be extracted via LPE. We do have an issue logged (internal bug-tracker id: VMAX-13218 ), however. I'll add your request to it as well. As a workaround, you can render the flakes only through LPE by using the 'mflakes' label like so:

C.'mflakes'.*

Afterward, extract the flakes from the VRaySpecular.

[sschierwater]

Thanks for the response Aleksandar, we are using a custom flakes shader, so unfortunately we will have to find a different work-around. Thanks again!

[sschierwater]

Hi Alex,

coming back to this issue, i just realized that i can't get a correct reflection of my shadow catcher plane even with the build in passes.. second image is showing the specular render element
i believe this was possible in previous versions or am i doing something wrong here?

matte for secondary rays is set to: with projection mapping and the hrdi texture is plugged into the enviroment overwrite slots in the rendersettings.

[hermit.crab]

The missing info should be in the Reflection pass. Back before Consistent Render Elements (check yellow paragraphs at the top) were introduced, it was in one pass.

[sschierwater]

Hi Alex,

the reflection pass is completly black. I've attached my testfile.
The correct reflection of the shadow only happens in the Beauty, but in none of the passes from the back to beauty preset.

[hermit.crab]

I am getting identical results between the RGB and BackToBeauty composition. The reflection pass is not empty. Tested with the latest official version. Attaching the reflection pass. Which V-Ray and Maya version are you using?

[sschierwater]

Hey Alex, thanks for testing.
Thats very weird. We're using V-Ray 6 for Maya, update 2 (v6.20.00 from Feb 12 2024) with Maya2022


I will try updating to the latest version and see if that fixes it.

[sschierwater]

Hi Alex,

i just tested with the latest version and that works. Seems like there was a bug in v6.20.00.
Thanks again for testing.

We still hope one day LPE's will work with matte reflections, because this would make our workflow with photgraphed backplates much easier.

[sschierwater]

Hey Alex,

i did notice the coat reflection pass doesn't seem to support matte objects either.
It shows the shadow catcher plane as a flat grey plane like the lPE's do. Is that a known limitation or a bug?

[hermit.crab]

Hey Alex,

i did notice the coat reflection pass doesn't seem to support matte objects either.
It shows the shadow catcher plane as a flat grey plane like the lPE's do. Is that a known limitation or a bug?

It's a bug. I've logged it (internal bug-tracker id: VMAYA-12997) for dev investigation.