Symptom: terrain renders pure black in modern path (legacy renderer
correct). Diagnostic at TerrainModernRenderer.Draw showed:
glProgramUniformHandle(prog=4, loc=5, handle=0x100251xxx) → GL_INVALID_OPERATION (0x0502)
on both terrain and alpha sampler uniforms.
Root cause: the `uniform sampler2DArray` + glProgramUniformHandleARB
combination is rejected by the NVIDIA Windows driver in this configuration.
The handle is valid and resident; the uniform location is valid; the
program is valid; but the driver refuses to bind a 64-bit handle to a
sampler uniform via the program-uniform path.
Fix: switch to N.5's mesh_modern pattern — pass each 64-bit handle as a
`uniform uvec2` (low + high 32-bit halves) and construct the sampler at
the use site via the GLSL `sampler2DArray(handle)` constructor. This
form is what ARB_bindless_texture documents as universally supported and
is what N.5 already uses successfully.
Files:
- terrain_modern.frag: replace `uniform sampler2DArray uTerrain/uAlpha`
with `uniform uvec2 uTerrainHandle/uAlphaHandle` + `#define`s
- TerrainModernRenderer.cs: cache uvec2 uniform locations; set via
`glProgramUniform2(program, loc, low32, high32)` per frame
- BindlessSupport.cs: remove now-unused `SetSamplerHandleUniform`,
leave a comment noting why the helper was retired
- GameWindow.cs: also strip the temporary [TERRAIN-DBG] cursor-wrap
print added during the perf-baseline investigation
Build green; 114/114 tests in N.5+N.5b filter still pass; user-verified
terrain renders correctly in modern path post-fix. Captured fresh perf
baseline:
- 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 call)
Modern is ~4× slower on CPU at radius=5 because the chunked legacy path
already collapsed the scene to one draw call. The architectural wins
(zero glBindTexture/frame; constant-cost dispatch as A.5 raises radius)
will be documented in T10's perf baseline doc; the spec's
"≥10% lower CPU" acceptance criterion is invalid at radius=5 and needs
revision.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Fragment shader for the modern terrain dispatcher. Bit-identical math
to today's terrain.frag (per-cell maskBlend3 + Phase G fog + lightning
flash). Same #version 460 + GL_ARB_bindless_texture preamble change
as terrain_modern.vert. Sampling syntax unchanged — the bindless-ness
is invisible at the GLSL level.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
