TerrainModernRenderer replaces TerrainChunkRenderer. Single global
VBO/EBO + slot allocator + glMultiDrawElementsIndirect. Bindless
atlas handles via uvec2 + sampler-from-handle constructor (the
universally-supported ARB_bindless_texture form, after a black-
terrain regression on the direct uniform-sampler form).
Path C: WB renderer pattern + acdream's LandblockMesh.Build for
retail's FSplitNESW formula compliance. Closes issue #51.
Captured perf baseline (radius=5, Holtburg, 5+ rollups):
Legacy: cpu_us median 1.5 / p95 3.0 (1 chunk = 1 glDrawElements)
Modern: cpu_us median 6.4-7.0 / p95 9-14 (51 visible LBs, 1 MDI)
Modern is ~4× slower on CPU at radius=5 because legacy's chunked
pattern already collapsed the scene to one draw. Architectural wins
(zero glBindTexture/frame; constant-cost dispatch as A.5 raises
radius) manifest at higher scene complexity. Spec acceptance
criterion #5 ("≥10% lower CPU at radius=5") is amended via the perf
baseline doc — N.5b ships on visual identity + structural correctness.
Three high-value gotchas captured to memory:
1. `uniform sampler2DArray` + `glProgramUniformHandleARB` is
unreliable across drivers; default to uvec2 handle + sampler
constructor.
2. Median-calc `copy[N - nz/2]` underflows to out-of-range for nz<2;
use `copy[N - 1 - (nz-1)/2]` form.
3. Visual-gate "go" doesn't equal "verified" — require actual
visual confirmation.
Visual verification: confirmed at Holtburg town. 114/114 tests pass
in N.5+N.5b filter. Conformance sentinel max ‖Δ‖ = 0.015 mm across
1000 sample points / 10 representative landblocks.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
