Limited Light material on multisub

[ChuckRT]

Hi i wanted to know if theres an update on this, i know that the solution is to use mesh light but sometimes its very time consuming to separate those elements, i have noticed that lightmaterials can be mutiplied in light mix, thats a very useful aproach but its limited by the material multiplier (being 30 the highest value)

[Vizioen]

Hi i wanted to know if theres an update on this, i know that the solution is to use mesh light but sometimes its very time consuming to separate those elements, i have noticed that lightmaterials can be mutiplied in light mix, thats a very useful aproach but its limited by the material multiplier (being 30 the highest value)

What do you mean being 30 the highest value? Afaik there's no limit of the multiplier in lightmtl. In lightmix the limit is 999.

[matanov]

Hi Carlos,

Can you give me a step by step what you are trying to achieve and what's not working?

[ChuckRT]

Hi matanov
Several assets has Lightmaterial in a multi/sub-object material, the vraylight material multipler can be setted to 1,000,000,000 but having it on multisub it limits the light for a value like 30 (or less)
When using Lightmix you can multiply this value for 999 likeVizioen said, but sometimes this produces noise or artifacts or some other issues because its forcing the original value for the multisub (which like I said, its something from 30 or less value)
To solve it you need to detach the element or polygon that has the lightmaterial and use it individually or detach and convert it as light mesh (doing this could be time consuming specially in heavy scenes)
This is known limitation that has been in Vray for along time, I was wondering if you could take a look of this again and try to solve it.
The attached image is a simple scene where the object of the Right has a lightmaterial on multisub and the left one is detached and assigned individually, they have the same material, but the detached produces more light like its suppose

[Vizioen]

Just tested this on CPU and GPU, I don't have that problem, and never noticed this either. Which Vray and CPU or GPU + Max and can you provide a scene?

[ChuckRT]

Im using Vray 6.2 latest nightly with 3ds max 2025 in Vray CPU
Like I said this problem has existed since forever
I attach the simple scene in max 2022 hope this helps

[Vizioen]

Aah you meant with direct illumination enabled. Indeed that doesn't seem to work. And that explains the problem I had a while back. 9 years, not enough people asking for it in the meantime I guess. +1 for me.

[vladimir_krastev]

The issue is reported as a bug in our system (VMAX-14299). I will link this thread to it.

[matanov]

The problem is that direct illumination turns the geometry into actual V-Ray lights which in the context of multi-sub objects can very problematic. The instability and slowdowns that such change might introduce are just not worth it as this thing has a workaround.

[ChuckRT]

I was hoping that you could integer the Corona solution, where the light material is not affected by this, I know that both are different engines and codes, but I dont know, maybe study a different aproach

[Vizioen]

My problem was that I had a railclone creating an office ceiling with everything in one sub material. I have circumvented the problem by also adding vraylights in the railclone, it works fine, but I can imagine other scenarios where a multisub with a light material for direct illumination might be the best solution.