With the recent discussions related to gamma handling I thought I'd post 
an image comparing how transmit behaves with respect to assumed_gamma in 
a texture overlaid upon an image base texture. The behavior of transmit 
at an assumed_gamma (ag) of 1.0 is something I like less well than its 
behavior at an ag of 2.2.

In the attached image I am comparing ag of 1.0 to an ag of 2.2 in each row.

There is a base image_map texture on a plane. Over the top of that 
texture is another with 5 columns of 4 colors (0,0.5,1.0,2.0) where the 
5 columns have transmit values of: 0,0.5,1.0,1.5,2.0. One parallel light 
source, camera orthographic, ambient 0, diffuse 1.0.

The non-linear behavior of transmit in the ag 2.2 case is often helpful 
to the final appearance of layered textures - the gray out region is 
tighter. When trying to map a 2.2 texture say from Norbert's collection 
into my ag 1.0 working space, I start by converting any rgb colors to 
srgb (bottom row), but that is usually not enough if the transmit value 
in any part of the texture is not 0.0 or 1.0.

I usually end up thrashing around with colors and transmit values to get 
closer, but truth is I'm often not able to match exactly the ag 2.2 
look. Might be different if I started from scratch I guess.

Am I missing some technique? Are there proposals in the works - or 
better available - which might help?

Aside: I have been wondering for a while about a more probabilistic 
pixel based transmit mode for blending overlapping textures. Might such 
an approach help with the dulling/graying of overlapping partly 
transparent textures...

Bill P.

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