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fix: clustered lighting packed decode stability on Samsung WebGL #8461

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Merged
mvaligursky merged 1 commit into from
Feb 14, 2026
Merged

fix: clustered lighting packed decode stability on Samsung WebGL #8461

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43 changes: 20 additions & 23 deletions src/scene/shader-lib/glsl/chunks/lit/frag/clusteredLight.js
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Original file line number Diff line number Diff line change
Expand Up @@ -44,9 +44,6 @@ uniform vec2 shadowAtlasParams;
// it's sorted to have all vectors aligned to 4 floats to limit padding
struct ClusterLightData {

// 32bit of flags
uint flags;

// area light sizes / orientation
vec3 halfWidth;

Expand Down Expand Up @@ -88,16 +85,10 @@ struct ClusterLightData {
// compressed biases, two haf-floats stored in a float
float biasesData;

// blue color component and angle flags (as uint for efficient bit operations)
uint colorBFlagsData;

// shadow bias values
float shadowBias;
float shadowNormalBias;

// compressed angles, two haf-floats stored in a float
float anglesData;

// spot light inner and outer angle cosine
float innerConeAngleCos;
float outerConeAngleCos;
Expand All @@ -118,6 +109,12 @@ struct ClusterLightData {
// shadow (spot light only) / cookie projection matrix
mat4 lightProjectionMatrix;

// NOTE: On some Samsung devices, these values can suffer precision / corruption issues when stored
// as members of ClusterLightData. Keep them as module-scope temporaries instead. See issue #7800.
uint clusterLightData_flags; // 32bit of flags
float clusterLightData_anglesData; // compressed angles, two haf-floats stored in a float
uint clusterLightData_colorBFlagsData; // blue color component and angle flags (as uint for efficient bit operations)

vec4 sampleLightTextureF(const ClusterLightData clusterLightData, int index) {
return texelFetch(lightsTexture, ivec2(index, clusterLightData.lightIndex), 0);
}
Expand All @@ -131,13 +128,13 @@ void decodeClusterLightCore(inout ClusterLightData clusterLightData, int lightIn
vec4 halfData = sampleLightTextureF(clusterLightData, {CLUSTER_TEXTURE_COLOR_ANGLES_BIAS});

// store floats we decode later as needed
clusterLightData.anglesData = halfData.z;
clusterLightData_anglesData = halfData.z;
clusterLightData.biasesData = halfData.w;
clusterLightData.colorBFlagsData = floatBitsToUint(halfData.y);
clusterLightData_colorBFlagsData = floatBitsToUint(halfData.y);

// decompress color half-floats
vec2 colorRG = unpackHalf2x16(floatBitsToUint(halfData.x));
vec2 colorB_flags = unpackHalf2x16(clusterLightData.colorBFlagsData);
vec2 colorB_flags = unpackHalf2x16(clusterLightData_colorBFlagsData);
clusterLightData.color = vec3(colorRG, colorB_flags.x) * {LIGHT_COLOR_DIVIDER};

// position and range, full floats
Expand All @@ -152,21 +149,21 @@ void decodeClusterLightCore(inout ClusterLightData clusterLightData, int lightIn
clusterLightData.direction = lightDir_Flags.xyz;

// 32bit flags
clusterLightData.flags = floatBitsToUint(lightDir_Flags.w);
clusterLightData.isSpot = (clusterLightData.flags & (1u << 30u)) != 0u;
clusterLightData.shape = (clusterLightData.flags >> 28u) & 0x3u;
clusterLightData.falloffModeLinear = (clusterLightData.flags & (1u << 27u)) == 0u;
clusterLightData.shadowIntensity = float((clusterLightData.flags >> 0u) & 0xFFu) / 255.0;
clusterLightData.cookieIntensity = float((clusterLightData.flags >> 8u) & 0xFFu) / 255.0;
clusterLightData.isDynamic = (clusterLightData.flags & (1u << 22u)) != 0u;
clusterLightData.isLightmapped = (clusterLightData.flags & (1u << 21u)) != 0u;
clusterLightData_flags = floatBitsToUint(lightDir_Flags.w);
clusterLightData.isSpot = (clusterLightData_flags & (1u << 30u)) != 0u;
clusterLightData.shape = (clusterLightData_flags >> 28u) & 0x3u;
clusterLightData.falloffModeLinear = (clusterLightData_flags & (1u << 27u)) == 0u;
clusterLightData.shadowIntensity = float((clusterLightData_flags >> 0u) & 0xFFu) / 255.0;
clusterLightData.cookieIntensity = float((clusterLightData_flags >> 8u) & 0xFFu) / 255.0;
clusterLightData.isDynamic = (clusterLightData_flags & (1u << 22u)) != 0u;
clusterLightData.isLightmapped = (clusterLightData_flags & (1u << 21u)) != 0u;
}

void decodeClusterLightSpot(inout ClusterLightData clusterLightData) {
// decompress spot light angles
uint angleFlags = (clusterLightData.colorBFlagsData >> 16u) & 0xFFFFu; // Extract upper 16 bits as integer
uint angleFlags = (clusterLightData_colorBFlagsData >> 16u) & 0xFFFFu; // Extract upper 16 bits as integer

vec2 angleValues = unpackHalf2x16(floatBitsToUint(clusterLightData.anglesData));
vec2 angleValues = unpackHalf2x16(floatBitsToUint(clusterLightData_anglesData));
float innerVal = angleValues.x;
float outerVal = angleValues.y;

Expand Down Expand Up @@ -207,7 +204,7 @@ void decodeClusterLightShadowData(inout ClusterLightData clusterLightData) {
void decodeClusterLightCookieData(inout ClusterLightData clusterLightData) {

// extract channel mask from flags
uint cookieFlags = (clusterLightData.flags >> 23u) & 0x0Fu; // 4bits, each bit enables a channel
uint cookieFlags = (clusterLightData_flags >> 23u) & 0x0Fu; // 4bits, each bit enables a channel
clusterLightData.cookieChannelMask = vec4(uvec4(cookieFlags) & uvec4(1u, 2u, 4u, 8u));
clusterLightData.cookieChannelMask = step(1.0, clusterLightData.cookieChannelMask); // Normalize to 0.0 or 1.0
}
Expand Down