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fix(shader): reduce specular aliasing on envAtlas reflections #8955

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fix(shader): reduce specular aliasing on envAtlas reflections #8955

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3c0bfb0
fix(shader): reduce specular aliasing on envAtlas reflections
willeastcott Jun 23, 2026
5edb1ca
Merge branch 'main' into fix/specular-aliasing-envatlas
willeastcott Jun 23, 2026
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30 changes: 15 additions & 15 deletions src/scene/shader-lib/glsl/chunks/lit/frag/reflectionEnv.js
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Original file line number Diff line number Diff line change
Expand Up @@ -25,32 +25,32 @@ vec3 calcReflection(vec3 reflDir, float gloss) {
vec3 dir = cubeMapProject(reflDir) * vec3(-1.0, 1.0, 1.0);
vec2 uv = toSphericalUv(dir);

// calculate roughness level
// roughness mip level based on material gloss
float level = saturate(1.0 - gloss) * 5.0;
float ilevel = floor(level);

// accessing the shiny (top level) reflection - perform manual mipmap lookup
// screen-space minification level - drives specular anti-aliasing
float level2 = shinyMipLevel(uv * atlasSize);
float ilevel2 = floor(level2);

// the reflection must be at least as blurry as screen-space minification requires,
// otherwise high-curvature / minified surfaces alias badly
level = max(level, level2);

float ilevel = floor(level);

vec2 uv0, uv1;
float weight;
if (ilevel == 0.0) {
uv0 = mapShinyUv(uv, ilevel2);
uv1 = mapShinyUv(uv, ilevel2 + 1.0);
weight = level2 - ilevel2;
// sharp reflection: blend the shiny (top mip) level into roughness level 1
uv0 = mapShinyUv(uv, 0.0);
uv1 = mapRoughnessUv(uv, 1.0);
} else {
// accessing rough reflection - just sample the same part twice
uv0 = uv1 = mapRoughnessUv(uv, ilevel);
weight = 0.0;
// blurry reflection: blend two pre-convolved roughness levels
uv0 = mapRoughnessUv(uv, ilevel);
uv1 = mapRoughnessUv(uv, ilevel + 1.0);
}

vec3 linearA = {reflectionDecode}(texture2D(texture_envAtlas, uv0));
vec3 linearB = {reflectionDecode}(texture2D(texture_envAtlas, uv1));
vec3 linear0 = mix(linearA, linearB, weight);
vec3 linear1 = {reflectionDecode}(texture2D(texture_envAtlas, mapRoughnessUv(uv, ilevel + 1.0)));

return processEnvironment(mix(linear0, linear1, level - ilevel));
return processEnvironment(mix(linearA, linearB, level - ilevel));
}

void addReflection(vec3 reflDir, float gloss) {
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31 changes: 15 additions & 16 deletions src/scene/shader-lib/wgsl/chunks/lit/frag/reflectionEnv.js
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Original file line number Diff line number Diff line change
Expand Up @@ -26,34 +26,33 @@ fn calcReflection(reflDir: vec3f, gloss: f32) -> vec3f {
let dir: vec3f = cubeMapProject(reflDir) * vec3f(-1.0, 1.0, 1.0);
let uv: vec2f = toSphericalUv(dir);

// calculate roughness level
let level: f32 = saturate(1.0 - gloss) * 5.0;
let ilevel: f32 = floor(level);
// roughness mip level based on material gloss
var level: f32 = saturate(1.0 - gloss) * 5.0;

// accessing the shiny (top level) reflection - perform manual mipmap lookup
// screen-space minification level - drives specular anti-aliasing
let level2: f32 = shinyMipLevel(uv * atlasSize);
let ilevel2: f32 = floor(level2);

// the reflection must be at least as blurry as screen-space minification requires,
// otherwise high-curvature / minified surfaces alias badly
level = max(level, level2);

let ilevel: f32 = floor(level);

var uv0: vec2f;
var uv1: vec2f;
var weight: f32;
if (ilevel == 0.0) {
uv0 = mapShinyUv(uv, ilevel2);
uv1 = mapShinyUv(uv, ilevel2 + 1.0);
weight = level2 - ilevel2;
// sharp reflection: blend the shiny (top mip) level into roughness level 1
uv0 = mapShinyUv(uv, 0.0);
uv1 = mapRoughnessUv(uv, 1.0);
} else {
// accessing rough reflection - just sample the same part twice
// blurry reflection: blend two pre-convolved roughness levels
uv0 = mapRoughnessUv(uv, ilevel);
uv1 = uv0;
weight = 0.0;
uv1 = mapRoughnessUv(uv, ilevel + 1.0);
}

let linearA: vec3f = {reflectionDecode}(textureSample(texture_envAtlas, texture_envAtlasSampler, uv0));
let linearB: vec3f = {reflectionDecode}(textureSample(texture_envAtlas, texture_envAtlasSampler, uv1));
let linear0: vec3f = mix(linearA, linearB, weight);
let linear1: vec3f = {reflectionDecode}(textureSample(texture_envAtlas, texture_envAtlasSampler, mapRoughnessUv(uv, ilevel + 1.0)));

return processEnvironment(mix(linear0, linear1, level - ilevel));
return processEnvironment(mix(linearA, linearB, level - ilevel));
}

fn addReflection(reflDir: vec3f, gloss: f32) {
Expand Down