radianceCubeSize property

Base-mip face size of the prefiltered radiance cubemap new environments build (the convolved reflection/ambient cube). Higher is sharper reflections at more memory (a cube is 6 * size^2 texels plus mips); 256-512 is a good default, up to ~2048. Equivalent to Godot's Sky.radiance_size. Applies only on backends that build the cube (see effectiveMipRadianceLayout); affects environments built afterward.

It also bounds how sharp the visible sky reads overhead: the background samples the full-resolution source across the horizon, but hands off to this cube's band 0 toward the poles, where the source's equirect mapping star-bursts. Raise it for a high-resolution HDR whose zenith looks soft.