Everything before this made the air a COLOUR APPLIED TO A SURFACE. Nothing put light
in the space between surfaces, so the basin had no shafts, no pooled mist and no rays
off a ridge at any hour, whatever was done to the fog.
A half-resolution march from the camera to the depth buffer, asking the same shadow
the rest of the frame asks - the cascades, the baked height-field shadow and the cloud
mask - so a shaft is cast by the actual trees and the actual ridge and a passing cloud
dims its own rays. Henyey-Greenstein scattering, because real air throws light forward.
Density and a separate ground-hugging mist layer ride the sun's elevation, so mist
forms in the cold at either end of the day and burns off by mid-morning.
Composited with the bloom pyramid's own tent upsample under ONE/ONE - what was wanted
and already there - and before bloom, so a shaft blooms. Into post_hdr, not post_scene:
post_scene is what the water refracts and shafts added there would sit under the lake.
The tuning that mattered was the sky term, which is added at every step: at 0.06 it
accumulated into a flat grey wash lifting lit and shadowed air equally, which is the
contrast a shaft is made of, and the valley came out one pale sheet. At 0.012 the sun
dominates and there is light rather than fog. I cut the density and mist three times
before the frame looked like air instead of paint.
R3D_NOVOL=1 for an A/B; Off in Settings skips the pass whole.
400 frames at 07:00: GL 7.1 -> 7.3 s, VK 7.2 -> 7.4 s. Backends agree to 0.08/255.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Grass (Vulkan with multi-draw indirect): every visible tile is a record in one buffer, uploaded once a
frame, and each band draws its records 256 at a time. A record's firstInstance is its place in the
chunk times 65536; grass.vert's TILES variant reads that place's corner and indices per cell from
u_tiles. R3D_GRASS_TILES=1 keeps a draw per tile. OpenGL is unchanged.
Casters: a LOD level with no impostor is drawn into a shadow cascade only when its distance band,
widened by six times its height, the camera's height over the ground and the frustum's corner reach,
can touch that cascade's receivers. The flowers' mesh levels (6 - 30 m) leave the three outer
cascades. R3D_CAST_ALL=1 draws every level everywhere. OpenGL frames byte-identical at all five
viewpoints; alpha-tested shadow draws at a 460 -> 244.
gpu_has_mdi() guards both this and the GPU-culled trees' multi-record draws.
Camp: Mac Vulkan 2645 -> 2191 (grass) -> 2034 draws; PC 2657 -> 2046, self-tests 59/59, validation 0.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
