Vray RT does`t reflect HDRI gamma value.

V-Ray V-Ray for 3ds Max Issues
1

Hi. I work with light dome + Vray HDRI and tuning the scene with RT GPU.
When HDRI gamma is set to 1 everything works well - image1.
When i want to increase contrast of HDRI by changing HDRI gamma value
RT output goes completely wrong - image2.
Is this a bug or is this not implemented to RT yet?
Best regards,

Jozef

gamma1.jpg
gamma1.jpg1540×1051 343 KB

gamma075.jpg
gamma075.jpg1534×1042 354 KB

2

I’ve had trouble with this as well. Actually, lately any RT renders don’t look at all like the regular ones. It worked fine in 1.5 but since then I haven’t had any luck with RT. People at work reporting the same thing… maybe a max/vray gamma problem? Not sure there.

3

Thanks Deflaminis, i though i was the only one having this problem.
Or i was the only one doing something wrong.

I have spent a lot of money for 3 x GTX680 to work with RT GPU.
Now i see it doesn`t work well with my usual scene lighting. Very sad…for me.

Hello Vlado. Bug hunt continues. Any reply?
Best regards,

Jozef

4

Currently the RT engine applies the gamma and the multiplier in reverse order to the production renderer, which leads to these differences, and this is a known issue. This will be fixed, but in any case applying gamma to a HDR image doesn’t make much sense in the first place (since it’s supposed to be already in linear space).

@Deflaminis - I think you are talking about a different problem, since what Jozef describes has been like that even in the 1.5 builds.

Best regards,
Vlado

5

Hello Vlado,

i mean this way of using gamma value of HDRI-s:

http://www.cgskies.com/resources\_tutorial\_rendering.php

Or is there any other way to achieve same result without changing gamma value?
Best regards,

Jozef

6

You could pipe the texture through a Color Correction node and change the gamma there, it should work fine.

Best regards,
Vlado