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IfcOpenShell/src
Dion Moult 4596f2e584 wgpu backend: lighting parity, MSAA, cavity shading, fix sRGB output
Closes the visible gap to BonsaiViewer down to just the post-process
edge silhouette pass (still pending in task #9). Four changes bundled
because together they bring up the parity story:

  - WGSL fragment now applies cavity = clamp(length(fwidth(n))*1.5,
    0, 0.35) and multiplies by (1 - cavity). Matches GL shader.

  - Lighting constants switched to GL's exact values: key (0.3, 0.5,
    0.8), fill (-0.3, -0.5, 0.8), sky tint (0.55, 0.60, 0.70), ground
    tint (0.35, 0.32, 0.28). My initial guesses were close but not
    identical; matching them means side-by-side diffs only flag actual
    pipeline differences, not lighting tweaks.

  - 4× MSAA: render pass writes into a MULTISAMPLE color attachment
    (surface_format_-matched), resolves into the surface texture for
    present. Depth is also 4 samples. Pipeline.multisample.count = 4.
    ensureMsaaColorTexture / releaseMsaaColorTexture mirror the depth-
    texture lifecycle. Matches GL minimal's QSurfaceFormat::setSamples(4).

  - sRGB output fix. wgpu-native's Vulkan swap chain on X11 treats
    BGRA8Unorm as sRGB-output (applies linear→sRGB encoding on shader
    writes), even though caps.formats[0] reports plain Unorm. The GL
    backend writes to a non-sRGB framebuffer with no such conversion,
    so a clearValue of (0.125, 0.137, 0.161) lands as bytes (32, 35,
    41) on GL but (99, 104, 112) on wgpu — ~3× brighter. Pre-decoding
    via srgbToLinear on (a) the clearValue in C++ and (b) the final
    fragment colour in WGSL makes wgpu's implicit encode round-trip,
    so the final bytes match GL. Verified via screenshot pixel sample:
    #202329 background reads as exactly (32, 35, 41).

Remaining visible gap to BonsaiViewer is the dark-line edge silhouettes
(renderEdgePass in GL, depth laplacian → outline). That belongs with
the overlay / post-process work in task #9.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
2026-05-27 14:44:13 +10:00
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