What gamma ! Tweet

[BorisGoreta]

I have a diffuse material with a diffuse color specified. I then create an image in PS with the exact same RGB values and load it in Texture Image node and connect it to Diffuse input and I don't get the same result. I need to set the Texture Image gamma to 1.0 for the same result.

What are the correct gamma values and settings on Preferences->CS for Octane to function proprly ?

Do I need to set gamma value of Texture images to 1 or leave it at 2.2 ?

[juanjgon]

I am not sure Boris, I always have problems to understand this kind of color space issues. AFAIK if you are working with the textures in a linear color space you should not correct them in the texture node, so gamma should be 1.0. For example the floating and HDRI images (in .exr or .hdr format) usually are lineal, so you don't need to correct them for rendering.

-Juanjo

[BorisGoreta]

I know, it was a mistery to me too but I was able to grasp it somewhat when linear workflow was introduced to LW.

I think that in Preferences->CS tab we should keep all settings on sRGB preset not Linear.

If I test a simple interior scene this way it works much better and textures look more like original images. Plus I get nicer results with much less bounces. This was the exact effect i got with LW renderer when going sRGB. What settings do you use ?

[juanjgon]

I know, it was a mistery to me too but I was able to grasp it somewhat when linear workflow was introduced to LW.

I think that in Preferences->CS tab we should keep all settings on sRGB preset not Linear.

If I test a simple interior scene this way it works much better and textures look more like original images. Plus I get nicer results with much less bounces. This was the exact effect i got with LW renderer when going sRGB. What settings do you use ?

Boris, this is not a good idea at all. Lightwave color space functions should be set to linear and use the Octane gamma and film response settings. The final images are not corrected using the LW color space functions, so if you use the LW gamma settings, the IPR and the final rendered image could not be the same. Also the Lightwave textures color space doesn't work at all with Octane, that read the files itself.

If you set in Octane a film response to linear, and a gamma of 2.2 you should get somthing similar like woking with Lightwave sRGB color space. You only need to correct the textures in the Octane texture node with a gamma 2.2 if you are working with not linear textures (for example usually the JPGs files), and leave the gamma correction in 1.0 for HDRI images.

-Juanjo

[geo_n]

Linear workflow is making all things that enter lightwave into linear space and all color and gradient tools to be based on linear space. So by setting lightwave cs into srgb we are subtracting gamma from all images and making colortools linear. That's what people don't get usually. Its more subtracting operation since jpeg,etc are all gamma 2.2 so we need to remove that before we feed it to the renderer.
This is the same with kray. If you put kray linear workflow master plugin it degamma all textures that kray will use.
Same for vray in 3dmax.
And then the renderer and display is added back gamma 2.2 so that everything is displaying a correct.

Does octane do this by default? That is the question. If it simply reads jpegs, etc then this is not linear workflow. We probably can subtract by using nodes every texture we use in a node flow but that could be tedious.

[juanjgon]

All render engines compute the rendering in linear color space. They need linear data for input (textures and colors), and they output a raw linear image.

Textures that are not linear (for example JPGSs) should be corrected, in Octane with the gamma parameter that you have in the texture image node, and the output should be corrected for display using the tonemappig/gamma settings available in the imager node.

-Juanjo

[geo_n]

Is it possible to add a global corrector for octane to use with 8 bit images?
Before vray, kray, lw had linear workflow it was necessary to add a color corrector to degamma jpegs, etc individually. But that was a long time ago. They have implemented global corrector since. Would be great to have this in octane v2.