lum_fill

Fills the LUMEN part's cathedral volume, one invocation per voxel. Drifting atmosphere is lit through an exact shadow trace against the westwork's opening layout — three lancets and the oculus — so the god rays are the geometry's own shafts rather than painted cones. A breathing ellipsoid halo of luminous air gathers around the extruded title and rises toward the oculus for the drop.

preseed/parts/p1_lumen.module owns this shader: it holds the reference, packs the U run each frame, and hands both to preseed/volume.module to dispatch.

Bindings

name	kind	what it is
vol	storage3d (rgba16f)	the volume written — RGB emission, A density
U	buffer (read, f32)	the part's fill parameters

U (f32 indices): 0 time · 1..3 light colour · 4 intensity · 5 atmosphere density · 6 scattering · 7 lancet half-width · 8 floor-pool gain · 9 oculus radius · 10 title halo gain · 11 halo lift (0 title → 1 oculus).