Every level of a kit tree or rock carries the same materials, so a GPU-culled layer merges each
material's levels into one mesh (layer_arena_build) and scatter_cull.comp writes a record per
(material, level) naming that level's index and vertex range; one indirect draw covers them all.
A conifer's lit pass and prepass go from 8 draws to 2, its shadow LOD from 6 to 2. Layers that do
not fit (card levels, other materials or attributes, 32-bit indices) keep the CPU path.
GPU culling is now the Vulkan default (R3D_GPU_CULL=0 turns it off). Camp benchmark, 400 frames:
PC 2791 -> 2657 draws, 4.3 -> 4.1 s (both runs); Mac 2791 -> 2657, 8.0/7.4 -> 7.7/7.2 s.
Self-tests 59/59 on both machines, PC validation 0 errors; frames within run-to-run noise; OpenGL
frames unchanged.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>