Light Select Limitation - Number of Light x Light Groups 15x4 -> 60 - Indirect Pass gets black

[Tyros]

Hi,

We got a big issue in production.
We are breaking our lights in 4 passes per light group, so we have more control in comp.

- Direct Diffuse
- Indirect Diffuse
- Direct Specular
- Indirect Specular

We tested all the latest Vray versions with simple scene spheres and planes for Maya 2020-2024 and all got the same problem.

The limit is 15 lights using the setup above. 15 lights x 4 = 60 light Select groups


Above 15 lights x4 = 60.
After this number, we can see direct diffuse and direct specular.
BUT Indirect Diffuse and Indirect Specular comes as BLACK for light select 16 or above. bellow still working.


We know we can group lights to minimize this issue.
But is this limitation correct or there is a bug?

Best

[hermit.crab]

I can't seem to reproduce it. It works fine on my end with more than 60 light select groups. Mind if you attach that simple setup so we can troubleshoot? Also, which V-Ray version build are you testing with?

[Tyros]

Hi Aleksandar,

I just attached previews which show the problem.
Also inside the ZIP file you can see the maya file simple test and a video showing the problem.
Light 16 Up, will get its indirect diffuse and specular as black

[hermit.crab]

Okay, I can confirm there's a limit of 64 individual light selects. There's a note about it in the LightMix docs, which should probably be on the VRayLightSelect page too. I suggest you group the lights in a certain way to avoid the limitation.
Maybe LPEs could come in handy too (i.e. combining indirect/direct specular into one pass). The LPE for Direct Specular + Indirect Specular should look like this:

C<R[GS]>(L|.+L)

[Tyros]

Hi Aleksandar,

My heart has now just been broken by this limitation
We are rendering a supermarket with several lights, pity not to be able to freely add lights and control in post. There is no way to remove this limitation by a scripting variable or somehow? or maybe a future update?

we will try grouping more lights

Thanks for the quick reply.

[Tyros]

Hi Aleksandar,

Sorry for asking again,
The limitation of 15 lights/groups for the split in 4 passes(Direct Diffuse, Indirect Diffuse, Direct Specular, and Indirect Specular) is so low.
Is there any variable that we could increase this value?
Or maybe a future fix?

Would you know why such a limitation?

[hermit.crab]

No such variable exists, I'm afraid. As I mentioned earlier, you could use LPEs to combine Direct Specular + Indirect Specular. If you render a Specular pass separately, you could extract it from the whole to get the Indirect Specular. To get the Direct Specular only extract the newly created Indirect Specular from the whole. Note that clamping is needed to get rid of the minus values from other lights' specular passes. This way you'll save at least 15 separate light select passes.

[Tyros]

ok
thanks Aleksandar