Making sense of textures in Gamma 2.2 workflow
http://viscorbel.com/making-sense-of-textures-in-gamma-2-2-workflow/
I’m pretty sure that at least 90% of you guys are using Gamma 2.2 workflow, just as you should be :)
It offers many advantages and works very well with pc monitors and human eyes.
There are a couple of problems that can arise, and quite often they are not very well explained or even mentioned.
Most of these concern the use of bitmaps and colors in materials.
The way it goes down is like this – once you set up to Gamma correct the Input, all the textures you load into max are corrected with the gamma curve.
3Ds max 2014 doesn’t even give you a choice, it does this automatically.
With most of the images this is absolutely fine, since photo-sourced textures should have the gamma correction applied…
however, there are a few special types of bitmaps that need a setting of 1.0
These are :
– B&W Maps where you want correct pixel values
– Displacement Maps
– Normal Maps
– Linear 32bit images like EXR or HDR (max 2014 takes care of these automatically)
How do you change the gamma? Simple, when loading in the bitmap, just set the Gamma to Override and input 1.0
Why should you care?
Here’s an example. In a Bump map, the middle grey value stays in it’s place, while lighter values move up and darker values move down.
So here is an example image, created in photoshop. Bump should be equally strong in both directions, right?
With the default gamma of 2.2, the result looks unbalanced, making the light tones stronger and the darks weaker. The image and the render do not match in a predictable way.
With the override set to 1.0, the result looks ‘exactly’ as you would expect.
Similar results can be achieved with normal maps, displacement maps, gloss maps, etc as well as any modifiers that use b&w maps to drive their values.
Using Gamma 1.0 for these maps is a MUST to get predictable results, where the pixel color values match with values they input in 3ds max.
The second problem is COLOR.
If you want to accurately reproduce the color from external application in 3Ds max (match a color from a photo, pantone palette, photoshop swatch, etc) this can be difficult, since the Gamma correction will wash out the color and produce a modified result.
For example, here’s a comparison of a Violet color [60;0;150] in photoshop, 3ds max material editor and render.
As you can see, these do not match at all!
To fix this, we must un-correct the color.
There are currently 2 ways to do this:
VrayColor map – set the Gamma to Specify and input 2.2
ColorCorrection map – in advanced settings use inverse Gamma to remove the correction 1/2.2=0.454
Both of these methods work, just use whichever you find easier to set up.
The result in Photoshop and render now matches perfectly!
I know this tut is a bit more technical than the others, but I believe that knowing how to fix little annoying things like these can help avoiding a lot of wasted time.