Physical correct materials- maximum reflectance of textures?

[Micha_cg]

Hi,

the theory says: the brightest white of the real world reflect approx. max. 80% of the light. So I set every white surface at (200,200,200). But my textures use the color space from 0 ... 255. In the past I have set the texture color black and the texture multiplier at 0.8. I

I ask me, if I don't like to set every texture at 0.8, can I use the secondary GI engine multiplier instead? Could I work physical correct with pure white (255,255,255) surfaces, if I set the secondary GI engine at 80%?

Ciao Micha

[flipside]

Physical correct materials- maximum reflectance of textures?

Not sure... Personally I also tend to do that, I never use secondary GI=1.0, as it can cause problems with infinite light bounces from perfectly white surfaces (especially with light cache as secondary GI).

Not sure if your 0.8*texture is correct either. If you use a texture for would for example which you made yourself from an existing picture, why would you darker it, after all you captured the real thing no?

Basically I don't care about physical correctness, if it looks right, it is right imo. I do use your point about pure white not existing. I don't go as low as 80% though. Same is for black, nothing is rgb 0,0,0 in real life.

The most physical correct approach is if you use the LWF method, which gijs is describing in the wiki. If you do that, you don't need any special color mappings, or GI saturation control, or invisible vraylights to brighten up interiors, or any other post process trick to make your render look real. Unfortunately, the LWF is hard to use in vfr because there is no gamma correction control for color swatches and choosers. Since I use the LWF method (which is basically gamma correction of your render), I don't wanna go back, and the lack of gamma correction in color swatches is seriously holding me back from using vfr as I can't live without LWF anymore. Especially with interior lighting and translucency, LWF is the key to success.

[Micha_cg]

Physical correct materials- maximum reflectance of textures?

Hallo Wouter,

thanks for your responce. I know you have much experience in VRay usage.

Not sure... Personally I also tend to do that, I never use secondary GI=1.0, as it can cause problems with infinite light bounces from perfectly white surfaces (especially with light cache as secondary GI).

What secondary GI multiplier do you prefer?

Not sure if your 0.8*texture is correct either. If you use a texture for would for example which you made yourself from an existing picture, why would you darker it, after all you captured the real thing no?

I see the problem, that a camera or the human eye see a relativ brightness. If I shot an image of a ground tile, than my camera dosn't set the brightest white at 80% (200,200,200). It's a question of the exposure. Here an example of a tile texture. I have disabled the preview of the histogram correction and set the mark at 200. You can see, much image information are above (200,200,200). Without GI I could take the texture like it is - classical no GI CG. But since we have got physical correct GI engines with unlimited bounces, we must be careful.

The most physical correct approach is if you use the LWF method ...

I see I must read it careful.

Two questions:

- Should we get a global color gamma correction for the material colors? Could it be enough? Or is a material based gamma correction necessary? I know very well the problem of the shifted, wrong colors.

- I like the "reinhard" mapping, because it seems to be the same like I know form the Maxwell control, that was very useful for me. It allow me to choose between full expontial color mapping like the human eye works, a medium color mapping like an analog film material catch the light or the limited color mapping of a digital camera CCD sensor. What did you think about the "reinhard" color mapping?

[flipside]

Physical correct materials- maximum reflectance of textures?

You should have gamma control in your color chooser, otherwise you can't choose a color you want. If it is gamma corrected, you immediately see the color how it will look like in your gamma corrected rendering.

Never used reinard mapping