Light colour (linear).
Procedural coverage.
Radiance of fully lit areas (0 = off).
Lights texture (equirectangular).
Planet radius, metres (sets the size of the sparkle).
Procedural feature scale.
Sun-elevation sines where lights switch on (start, full).
1 = use the texture, 0 = procedural.
Points the uniforms at a lights texture (or back to the procedural field with
null).