Smaller fog texture? (less color channels)

[illwieckz]

When working on the linear pipeline support for the fog¹, I noticed that, unless I'm wrong, the fog texture is an RGBA image but we only use the alpha channel, setting RGB to {1, 1, 1}.

We may instead store an image with less color components. Also by storing this alpha channel in something like a red channel, we may use sRGB variants and let the hardware do the sRGB conversions.

• ¹ tr_shader: linearize fog colors and fog image #1730

[VReaperV]

Yes, single channel would be enough here.