nebula_fill

Fills a volume with a spiral nebula: RGB carries emission, A carries density. One invocation per voxel at workgroup size 4x4x4.

Bindings

name	kind	what it is
vol	storage3d (rgba16f)	the volume written, read-write so a pass can accumulate
U	buffer (read, f32)	the demo's fill parameters, in the order the shader reads them

U holds: elapsed time, spiral frequency, arm thickness, core brightness, edge brightness, dust density, noise strength.