-Cloud shadows are rendered using the depth buffer instead of re-rendering most of the scene's geometry with a projector

-Celestial shadows are also rendered using the depth buffer instead of re-rendering most of the scene's geometry with a projector

-All the particles in a volumetric cloud layer are rendered at once in a single draw-call, instead of one draw-call per particle, saving CPU time

-One MeshRenderer and one GameObject per volumetric layer instead of one per particle

-Volumetric particles are rendered at 1/4 the screen resolution then upsampled with a depth-aware filter and composited into the scene, saving GPU power

Fixes:

-Volumetrics fade near the camera, more natural transition

-Fix 2D clouds fading into the planet when zooming out

-Fix issue where clouds are stuck when loading savegame from KSC

-Improve eclipse shading by making it softer and more natural