Multi-Res Performance Optimisation for Atmosphere + Clouds
Volumetric Raymarching can be Very Costly Volumetric Raymarching can be very costly as many 100s of ray-marching operations are performed on the GPU each pixel for each frame. A standard HD screen of 1920x1080 contains over 2 million pixels. In the case of my atmosphere + cloud shader, this high fill-rate cost brings the game's frame-rate to its knees. In order to play Pegwars with cool new clouds in smooth realtime and iterate on the shader, I had to shade the planet and everything within the planet's atmosphere to a half-width, half-height render target. This approach costs 1/4 of the fill-rate and renders around 4x faster, but the results as you can see are blocky and blurry. Especially the building edges and the horizon lines are badly aliased : Multi-Resolution Shading As the atmosphere / cloud shader is very much fill-rate limited, either optimise the number of shader instructions per-pixel, or reduce the number of pixels shaded. The goal...