LWF and Physical Camera

[dariofx]

Hi everyone. I'm currently using Vray for Maya 2.30.01 on Maya 2013 SP2.

I'm still fairly new to Vray for Maya, but getting the hang of it.

I also use a Linear Workflow setup and render to exr. The setup that I use is pretty much this one:

http://pixel-reality.com/linear-work...v-ray-for-maya

- Linear Multiply
- Gamma 2.2
- Don't Affect Colors (adaptation only)
- Affect Swatches
- Texture input gamma set to sRGB for non-linear textures
- VFB set to sRGB (LUT)

This is info that has been discussed and posted many times. Right.

So, my question is this. I just started working at a new studio using Vray for Maya, and the TD has just told me that they have linear workflow setup that is different. Basically the TD has indicated that as long as you are using a Vray physical camera, and leave the color mapping gamma set to 1.0, then you have a proper linear workflow. I asked him about non-linear textures and he indicated that its up to me weather I thought if they needed a gamma correction or not.

The main point that the TD was making to me, is that by using the Vray physical camera, it basically takes care of setting up a linear workflow in vray for maya, because it has built in gamma correction. Gamma correcting non-linear textures may still be needed.

Does this sounds correct to you guys? I'm a bit confused.

[ricorio]

Hey dariofx,

I don't think that the physical camera takes care of anything related to a linear workflow.
It just gives you physical properties for the camera like in the real world for instance fstop and iso to regulate the light intensity for your image.
You could test this in rendering a common maya camera and then a physical camera (play with the fstop and/or iso to get about the same exposure like with the non-physical camera).

So if you don't correct your 8bit color textures to linear in both rendered images the textures will look washed out (displaying the rendered image in gamma 2.2) which somehow proofs that
the physical camera doesn't change anything regarding the color values of your textures and doesn't have a build in gamma correction.

[dariofx]

Thanks for your help ricorio!

Any reply from Chaos Group? Vlado?

[Zdravko]

VRayPhysicalCamera doesn't affect the gamma settings. As Ricoroc said it just work in real-world parameters.
Also you can use "Linear workflow" option which will automatically apply the inverse gamma correction for all materials and textures in the scene for you. Without the one that are already linear like HDRI and OpenEXR.
Note that there are different approaches to do LWF, it is best to choose one and stick to it.

[MartinB]

On a slightly related note, when adjusting physical camera properties does the iso, f-stop etc work in linear steps. So going from ISO 100 to 200, the image/pixel values would be twice as bright across the image, or is it tone mapping it with a curve?

I'm generally not a fan of the physical camera, I think a combination of it having been buggy in the past and also different artists setting up shaders and lighting with different settings, then nothing matching between shots (Thats more of an issue with the studio and lack of pipeline/communication, it just seemed the physical camera introduced another potential stumbling block to deal with)

How do other people use it in production?

[Zdravko]

The options in V-Ray physical camera are linear as long as you use proper linear workflow.
VRayPhysicalCamera internally calculates colors linearly. If you apply gamma after the rendering the result will not be linear.