Strange colors by energy preservation

[Micha]

Hi,

I discussed it on the Rhino side, but got not the expected solution. I understand that V-Ray tries to be physical correct, but if the final result looks wrong than we need an other solution.

So far I understand we have two ways of energy preservation with two different results. The RGB method looks wrong and cause trouble, but for GPU mode this method is the only one. Please help and allow to use the HSV method in GPU mode too.

Best regards,
Micha


https://discourse.mcneel.com/t/one-o...erial/154043/8

[Muhammed_Hamed]

Hey Micha

Breaking PBR could lead to unsolvable noise or slower render times, it is not just about physical accuracy. It works out for the best that V-Ray clamps the diffuse/reflection values for energy preservation
Have you tried working with Metalness to change the color of your metals? (Matalness value could only be 0 or 1)
In this case Reflection Color is always white, Diffuse color is what you use to change the color of your metal. This is very easy to control and gives great results, if you have time please check this blog post about metalness in V-Ray

If you have some reference metals to match please share here, I can share my workflow and setup with you. I'm open minded on this one , if you convince me on the HSV mode I will add to the GPU roadmap

Best,
Muhammed

[Micha]

Hi Muhammed_Hamed,

The first thing I think is that a rendering engine should not simply produce a wrong, never intended, unreal look. Especially the function of phsical correctness should not produce a physically incorrect result. That sounds like a joke.

I often add a small amount of diffuse to metals to make them look older or to add some mattness in areas of dark reflections, such as aluminum. Especially with aluminum, the surface can change to a matt material - just think of an old milk jug. Or colored anodized aluminum.

I also often create paints with a small metallic component, a kind of pearl effect, to give them more depth. You can find this on cars, but I also use it for renderings of trains. That's where it's most annoying when other colours suddenly appear. That's where I see the main problem, because you can mix metal and plastic really finely from 0 to 1.

You write about using only metallness of 0 or 1, but especially when you use dirt maps and have a smooth transition of wear, that doesn't work. Just think of a piece of plastic with a metal coating that is already more or less worn in parts.

The RGB method is simply the wrong way to go if it leads to undesirable results. What's wrong with using the HSV method? Why not prevent undesirable results, especially if the HSV method already allows for CPU mode?


Here a desaturated red paint with clear finish and metal effect. The blue-greenish hue shift shouldn't be there.