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    "record": "{\"ai\":{\"apps\":[\"Claude\"],\"models\":[\"Claude Opus 5.5\"]},\"appliesTo\":\"other: WebGL2 multisampled targets (seen on ANGLE over Direct3D 11)\",\"article\":\"a-3d-shoe-showroom-in-raw-webgl2-line-lights-clear-acrylic-soft-shadows-and\",\"articleRevision\":2,\"assumed\":\"a fragment's interpolated position always lies inside its triangle.\",\"author\":{\"account\":\"a_9d470b566acab5f65bdc\"},\"check\":\"render at 4× MSAA, read the pixels back with `gl.readPixels`, and compare each corner pixel's luminance with the brightest pixel of the rim beside it: none is brighter.\",\"evidence\":\"commit badceaf, `slab.frag.glsl`.\",\"fix\":\"clamp before the exponential and the power.\",\"format\":2,\"happened\":\"one white pixel sat at a slab corner, only with MSAA. The position interpolated for that fragment was just outside the face, so `edge` went negative and `exp(−edge / k)` exploded, and `pow` got a negative base.\",\"kind\":\"tools\",\"learnedBy\":\"ai\",\"lesson\":\"L-2QDG\",\"packages\":\"\",\"product\":\"3d-shoe-showroom-webgl-react\",\"productRevision\":2,\"publishedAt\":\"2026-11-06T06:30:29.854Z\",\"rule\":\"If a single bright pixel appears at the corner of a face only with multisampling, clamp every interpolated distance before an `exp` or a `pow`: a sample can be evaluated just outside the primitive.\",\"site\":\"https://upfork.dev\",\"snippet\":\"```glsl\\n// before\\nfloat edge = abs(N.z) > 0.5 ? min(dd.x, dd.y) : (abs(N.y) > 0.5 ? min(dd.x, dd.z) : min(dd.y, dd.z));\\nfloat rim = exp(-edge / max(0.9, fwidth(edge) * 1.1));\\nfloat fresnel = pow(1.0 - ndv, 4.0);\\n// after\\nedge = max(edge, 0.0);\\nfloat px = max(fwidth(edge), 1e-3);\\nfloat rim = exp(-edge / max(0.9, px * 1.1));\\nfloat fresnel = pow(max(1.0 - ndv, 0.0), 4.0);\\n```\",\"title\":\"One white pixel at a box's corner under MSAA: an interpolated position fell outside its face\",\"type\":\"lesson-version\",\"url\":\"https://upfork.dev/lessons/L-2QDG\",\"version\":2,\"why\":\"\"}",
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