surf_cloudfill

Fills the CLOUDSURF part's cumulus bank, one invocation per voxel. A grid of cells in world x/z hosts one cauliflower tower each — a stack of lobes whose centres, radii and squash come from the cell hash, soft-unioned into one billowing mass and gnawed by fbm so the silhouette breaks into florets. The scroll parameter slides the grid through the box, so the parade passes the rider; towers grow with distance, so the near flank stays readable while the horizon bank stays massive.

Each voxel shades itself: the field sampled a step along the sun vector gives the transmittance carrying the dawn ramp — lilac in the shadowed core, cream-gold on the backlit rim, warmth spilled onto the crowns.

preseed/parts/p_surf.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 scroll z · 2..4 aabb min · 5..7 aabb max · 8 coverage · 9 density · 10..12 sun vector · 13 warmth · 14 light gain · 15 detail.