Custom Brightness

[Rachael]

This is the prototype that I used to create this feature: https://github.com/coelckers/gzdoom/com ... 00ac3f6889

This shader essentially allows much greater flexibility over the brightness/gamma presentation than GZDoom/Raze allows internally. Including allowing values that turn the image negative.

Its main purpose is to demonstrate how to define linked uniform CVars in gldefs.txt - which is preferred over using a tick function since now it does not need to run every frame, not to mention makes it actually usable in Raze.

[Redneckerz]

Looks trippy but also clean. I like the look a lot.

[grahf78]

Love the new feature. Is there any chance this could also get implemented for material shaders? It would also be nice to be able to subscribe some sort of cvar event listener in ZScript too, for cases where we need to check them every tick.