Thank you, @SebHillaire, I’ve got better evenings with only exponential height fog.
Okay, instructions don’t do anything (though some 1-2% FPS drop I’ve experienced) but I can’t keep calm if a simple operation of retrieving a sky color in a pixel or rendering a simple sun disk adds dozens of instructions to the shader. If a pixel is occupied by several translucent shaders, calcuations are duplicated, am I right? Okay, similar AtmosphericFog material expression is even more heavy, so I feel I’m missing something. Many years ago I tried to make my own dynamic sky system, it was in pure GLSL, it also used LUTs, but it wrote the result into vertex colors, so I needed a good topology of the skydome, taking into account sun trajectory, but it was extremely cheap on hardware supporting OpenGL 2.1 and nothing newer (+ free fake lens rays out of interpolation artefacts:p). It would be good if Sky Atmosphere allowed something like that (tried VertexInterpolator, did not compile).
Anyway, I have another question. Is it possible to render the sky without super-bright sun disks/glows? I mean default rendering without sky materials. I tried using Scene Capture Cube with Atmosphere flag, and it’s almost okay, but sun/moon disks are imprinted into the cubemap as freaky distorted clumps of HDR pixels, making the map good for distant reflections but ruined as ambient. Rendering as sky mesh is hardly possible as it captures many unwanted objects. The workaround is (temporary) setting the light source angle 0, but maybe there is (or will be) something like Disable sun disk flag in AtmosphericFog?