RectLight: textured light under a non-uniform scale samples and looks up the texture with the unscaled size

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Evaluación

Dificultad
3/5
Tiempo estimado
1-2 días
Aptitud para principiantes
57/100
Tipo de issue
Error
Claridad
Bien especificado
Estado de actividad
Activo
Stack tecnológico
cpp
Área
computer-graphics

Línea de trabajo

Read lib/rendering/pbr/light/RectLight.cc and Light.cc, especially RectLight::update(), updateParamAndTransforms(), and updateTransforms(). Reproduce the mismatch with a textured RectLight scaled by (2, 1, 1) and compare light-only with BSDF-only sampling. Done means both sampling paths agree for the scaled textured light, as they do for the unscaled equivalent.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

Summary. A textured RectLight whose node_xform scales it non-uniformly samples and looks up its texture with the unscaled size: light sampling and BSDF sampling disagree. Without the texture, or without the scale, both agree. Version 2026.29.1, scalar mode.

Reproduce. Diffuse floor, RectLight with width 1, height 1, a texture, scale(2, 1, 1) in node_xform, max_depth 1:

light light_samples only bsdf_samples only
width 1, scale(2, 1, 1), textured 0.0907 0.0715
width 2, no scale, textured 0.0892 0.0891

Cause. RectLight::update() (lib/rendering/pbr/light/RectLight.cc) sets mHalfWidth/mHalfHeight from the attributes and passes them by value to updateParamAndTransforms() (Light.cc). That function first calls updateTransforms(), which for a non-uniform scale multiplies mWidth/mHeight (and mHalfWidth/mHalfHeight) by the scale, and then builds the texture uv mapping (getScaleOffset) from the stale, unscaled values it was given. So sample() maps uv in [0, 1] to the middle part of the light only, while reporting the density of the whole area, and intersect() gives uv outside [0, 1] on the outer parts.

Fix (untested). Compute the uv mapping after updateTransforms(), e.g. pass the scaled half sizes, or set the uv scale and offset from the members after the call.

Lenguaje dominante
CMake
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13 min
PR fusionados (30 d)
3

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