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feat(skylighting): add per-probe shadow skylighting #2498

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1964e23
feat(skylighting): add per-probe shadow visibility from cascade map
claude May 24, 2026
43925e4
fix(skylighting): address review findings for shadow cascade probes
doodlum Jun 10, 2026
6db654b
refactor(skylighting): merge shadow visibility into Sample loop
doodlum Jun 10, 2026
bdfc81b
refactor(skylighting): restrict shadow visibility to rim/soft/back li…
doodlum Jun 10, 2026
53b85f0
fix(skylighting): guard degenerate normal and remove dead code
doodlum Jun 10, 2026
f92a988
fix(skylighting): use R8_UNORM for shadow visibility texture
doodlum Jun 10, 2026
2b909c2
fix(skylighting): correct GetShadowDepth call to single parameter
doodlum Jun 10, 2026
192aa0d
fix(skylighting): CameraPosAdjust is no longer an array post-VR removal
doodlum Jun 10, 2026
7c5af30
feat(skylighting): apply shadow visibility via dirSoftShadow replacement
doodlum Jun 10, 2026
b82cc26
fix(skylighting): revert unintended CommonLibSSE-NG submodule change
doodlum Jun 10, 2026
e1fdb61
fix(skylighting): define SKYLIGHTING_SHADOW_VIS before DynamicCubemap…
doodlum Jun 10, 2026
b3c48ef
refactor(skylighting): optimise dirSoftShadow path and clean up Sample
doodlum Jun 11, 2026
67843d5
fix(skylighting): restore basic tangent checks comment
doodlum Jun 11, 2026
e257767
fix(skylighting): prevent division by zero on accumFrames wrap
doodlum Jun 11, 2026
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81 changes: 48 additions & 33 deletions features/Skylighting/Shaders/Skylighting/Skylighting.hlsli
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,10 @@ namespace Skylighting
Texture3D<sh2> SkylightingProbeArray : register(t50);
#endif

#if defined(SKYLIGHTING_SHADOW_VIS)
Texture3D<float> ShadowVisibilityProbeArray : register(t53);
#endif

const static sh2 UNIT_SH = float4(sqrt(4.0 * Math::PI), 0, 0, 0);

const static uint3 ARRAY_DIM = uint3(256, 256, 128);
Expand Down Expand Up @@ -75,10 +79,18 @@ namespace Skylighting
#endif

#if defined(PSHADER) || defined(SKYLIGHTING_PROBE_REGISTER)
sh2 Sample(float3 positionMS, float3 normalWS)
sh2 Sample(float3 positionMS, float3 normalWS
#if defined(SKYLIGHTING_SHADOW_VIS)
, out float shadowVisibility
#endif
)
{
sh2 scaledUnitSH = UNIT_SH / 1e-10;

#if defined(SKYLIGHTING_SHADOW_VIS)
shadowVisibility = 1.0;
#endif

if (SharedData::InInterior)
return scaledUnitSH;

Expand All @@ -94,55 +106,63 @@ namespace Skylighting
int3 cell000 = floor(cellVxCoord - 0.5);
float3 trilinearPos = cellVxCoord - 0.5 - cell000;

sh2 sum = 0;
float wsum = 0;
sh2 shSum = 0;
float shWsum = 0;
#if defined(SKYLIGHTING_SHADOW_VIS)
float shadowSum = 0;
float shadowWsum = 0;
#endif

for (int i = 0; i < 2; i++)
for (int j = 0; j < 2; j++)
for (int k = 0; k < 2; k++) {
int3 offset = int3(i, j, k);
int3 cellID = cell000 + offset;
int3 cellOffset = int3(i, j, k);
int3 cellID = cell000 + cellOffset;

if (any(cellID < 0) || any((uint3)cellID >= ARRAY_DIM))
continue;

float3 cellCentreMS = cellID + 0.5 - ARRAY_DIM / 2;
cellCentreMS = cellCentreMS * CELL_SIZE;
float3 cellCentreMS = (cellID + 0.5 - ARRAY_DIM / 2) * CELL_SIZE;

float3 trilinearWeights = 1 - abs(cellOffset - trilinearPos);
float triW = trilinearWeights.x * trilinearWeights.y * trilinearWeights.z;

uint3 cellTexID = (cellID + SharedData::skylightingSettings.ArrayOrigin.xyz) % ARRAY_DIM;

// https://handmade.network/p/75/monter/blog/p/7288-engine_work__global_illumination_with_irradiance_probes
// basic tangent checks
float tangentWeight = dot(normalize(cellCentreMS - positionMSAdjusted), normalWS) * 0.5 + 0.5;
float shW = triW * tangentWeight;
shSum = SphericalHarmonics::Add(shSum, SphericalHarmonics::Scale(SkylightingProbeArray[cellTexID], shW));
shWsum += shW;

float3 trilinearWeights = 1 - abs(offset - trilinearPos);
float w = trilinearWeights.x * trilinearWeights.y * trilinearWeights.z * tangentWeight;

uint3 cellTexID = (cellID + SharedData::skylightingSettings.ArrayOrigin.xyz) % ARRAY_DIM;
sh2 probe = SphericalHarmonics::Scale(SkylightingProbeArray[cellTexID], w);

sum = SphericalHarmonics::Add(sum, probe);
wsum += w;
#if defined(SKYLIGHTING_SHADOW_VIS)
shadowSum += ShadowVisibilityProbeArray[cellTexID] * triW;
shadowWsum += triW;
#endif
}

return SphericalHarmonics::Scale(sum, rcp(wsum + EPSILON_WEIGHT_SUM));
#if defined(SKYLIGHTING_SHADOW_VIS)
float fadeOut = GetFadeOutFactor(positionMS);
shadowVisibility = lerp(1.0, shadowSum / max(shadowWsum, EPSILON_WEIGHT_SUM), fadeOut);
#endif

return SphericalHarmonics::Scale(shSum, rcp(shWsum + EPSILON_WEIGHT_SUM));
}

// Compute skylighting diffuse for a receiver biased to face upward (grass/foliage).
// The result is pre-divided by vertexAO so that a subsequent multiply by vertexAO
// yields min(skylightingDiffuse, vertexAO). Pass vertexAO = 1 to skip this compensation.
float GetVertexSkylightingDiffuse(float3 positionMS, float3 normalWS, float vertexAO)
float GetSkylightingDiffuse(sh2 skylightingSH, float3 positionMS, float3 evalNormal, float vertexAO = 1.0)
{
if (SharedData::InInterior)
return 1.0;

float3 candidateNormal = float3(evalNormal.xy, max(0.0, evalNormal.z));
float3 biasedNormal = dot(candidateNormal, candidateNormal) > 1e-6
? normalize(candidateNormal)
: float3(0, 0, 1);
float fadeOutFactor = GetFadeOutFactor(positionMS);

float3 biasedNormal = normalWS;
biasedNormal.z = max(0.0, biasedNormal.z);
biasedNormal = normalize(biasedNormal);

sh2 skylightingSH = Sample(positionMS, normalWS);
float skylightingDiffuse = EvaluateDiffuse(skylightingSH, biasedNormal, fadeOutFactor);

return saturate(skylightingDiffuse / max(vertexAO, 1e-5));
return saturate(skylightingDiffuse / max(vertexAO, EPSILON_DIVISION));
}

sh2 SampleNoBias(float3 positionMS)
Expand Down Expand Up @@ -174,16 +194,11 @@ namespace Skylighting
if (any(cellID < 0) || any((uint3)cellID >= ARRAY_DIM))
continue;

float3 cellCentreMS = cellID + 0.5 - ARRAY_DIM / 2;
cellCentreMS = cellCentreMS * CELL_SIZE;

float3 trilinearWeights = 1 - abs(offset - trilinearPos);
float w = trilinearWeights.x * trilinearWeights.y * trilinearWeights.z;

uint3 cellTexID = (cellID + SharedData::skylightingSettings.ArrayOrigin.xyz) % ARRAY_DIM;
sh2 probe = SphericalHarmonics::Scale(SkylightingProbeArray[cellTexID], w);

sum = SphericalHarmonics::Add(sum, probe);
sum = SphericalHarmonics::Add(sum, SphericalHarmonics::Scale(SkylightingProbeArray[cellTexID], w));
wsum += w;
}

Expand Down
93 changes: 92 additions & 1 deletion features/Skylighting/Shaders/Skylighting/UpdateProbesCS.hlsl
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Original file line number Diff line number Diff line change
@@ -1,13 +1,61 @@
#include "Common/FrameBuffer.hlsli"
#include "Common/Math.hlsli"
#include "Skylighting/Skylighting.hlsli"

Texture2D<unorm float> srcOcclusionDepth : register(t0);
Texture2DArray<float4> ShadowCascadeMap : register(t1);

struct DirectionalShadowLightData
{
column_major float4x4 ShadowProj[2];
column_major float4x4 InvShadowProj[2];
float2 EndSplitDistances;
float2 StartSplitDistances;
};
StructuredBuffer<DirectionalShadowLightData> DirectionalShadowLights : register(t2);
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RWTexture3D<sh2> outProbeArray : register(u0);
RWTexture3D<uint> outAccumFramesArray : register(u1);
RWTexture3D<uint> outShadowBitmask : register(u2);
RWTexture3D<float> outShadowVisibility : register(u3);

SamplerComparisonState comparisonSampler : register(s0);

static const float3 noise3D[32] = {
float3(0.247, -0.583, 0.891),
float3(-0.672, 0.315, -0.428),
float3(0.934, 0.762, -0.153),
float3(-0.391, -0.847, 0.526),
float3(0.618, 0.094, 0.739),
float3(-0.825, -0.271, -0.683),
float3(0.152, 0.968, 0.347),
float3(0.503, -0.714, -0.592),
float3(-0.436, 0.629, 0.814),
float3(0.887, -0.198, 0.461),
float3(-0.759, 0.852, -0.305),
float3(0.321, -0.476, -0.921),
float3(-0.094, 0.543, -0.768),
float3(0.776, 0.418, 0.632),
float3(-0.538, -0.695, 0.279),
float3(0.649, -0.921, 0.186),
float3(-0.913, 0.127, 0.574),
float3(0.285, 0.806, -0.447),
float3(0.471, -0.352, 0.698),
float3(-0.627, -0.194, -0.856),
float3(0.834, 0.591, -0.712),
float3(-0.173, -0.968, -0.421),
float3(0.562, 0.239, -0.785),
float3(-0.745, 0.487, 0.316),
float3(0.108, -0.631, 0.894),
float3(0.926, -0.845, -0.267),
float3(-0.384, 0.712, -0.539),
float3(0.697, 0.163, 0.825),
float3(-0.851, -0.429, 0.641),
float3(0.214, 0.934, 0.372),
float3(0.578, -0.762, -0.614),
float3(-0.469, 0.381, 0.947)
};

[numthreads(8, 8, 1)] void main(uint3 dtid : SV_DispatchThreadID) {
const float fadeInThreshold = 15;
const static sh2 unitSH = Skylighting::UNIT_SH;
Expand Down Expand Up @@ -39,8 +87,51 @@ SamplerComparisonState comparisonSampler : register(s0);

outProbeArray[dtid] = occlusionSH;
outAccumFramesArray[dtid] = accumFrames;

// Shadow cascade sampling with bitmask accumulation
{
float shadowSample = 1.0;
DirectionalShadowLightData shadowData = DirectionalShadowLights[0];

uint shadowFrames = max(accumFrames, 1u);
uint bitIndex = (shadowFrames - 1) % 32;
float3 jitteredMS = cellCentreMS + noise3D[bitIndex] * Skylighting::CELL_SIZE;

float ndcDepth = FrameBuffer::GetShadowDepth(jitteredMS);
float linearDepth = SharedData::GetScreenDepth(ndcDepth);

if (linearDepth > 0 && linearDepth < shadowData.EndSplitDistances.y) {
float3 positionWS = jitteredMS + FrameBuffer::CameraPosAdjust.xyz;

uint cascadeIndex = (linearDepth > shadowData.EndSplitDistances.x) ? 1u : 0u;

float3 positionLS = mul(shadowData.ShadowProj[cascadeIndex], float4(positionWS, 1)).xyz;

if (all(positionLS.xy >= 0) && all(positionLS.xy <= 1)) {
shadowSample = ShadowCascadeMap.SampleCmpLevelZero(comparisonSampler, float3(positionLS.xy, cascadeIndex), positionLS.z);
}

float fade = saturate(linearDepth / shadowData.EndSplitDistances.y);
float fadeFactor = 1.0 - pow(fade * fade, 8);
shadowSample = lerp(1.0, shadowSample, fadeFactor);
}

uint bitmask = isValid ? outShadowBitmask[dtid] : 0;
bitmask &= ~(1u << bitIndex);
if (shadowSample > 0.5)
bitmask |= (1u << bitIndex);

outShadowBitmask[dtid] = bitmask;

uint validBits = min(shadowFrames, 32u);
float shadow = float(countbits(bitmask)) / float(validBits);
shadow = lerp(1.0, shadow, min(fadeInThreshold, shadowFrames) / fadeInThreshold);
outShadowVisibility[dtid] = shadow;
}
} else if (!isValid) {
outProbeArray[dtid] = unitSH;
outAccumFramesArray[dtid] = 0;
outShadowBitmask[dtid] = 0;
outShadowVisibility[dtid] = 1.0;
}
}
}
40 changes: 33 additions & 7 deletions package/Shaders/Lighting.hlsl
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Original file line number Diff line number Diff line change
Expand Up @@ -786,6 +786,12 @@ float GetSnowParameterY(float texProjTmp, float alpha)
# undef SKYLIGHTING
# endif

# if defined(SKYLIGHTING)
# if defined(RIM_LIGHTING) || defined(SOFT_LIGHTING) || defined(LOAD_SOFT_LIGHTING) || defined(BACK_LIGHTING)
# define SKYLIGHTING_SHADOW_VIS
# endif
# endif

# include "Common/LightingCommon.hlsli"

# if defined(WATER_EFFECTS)
Expand Down Expand Up @@ -2408,12 +2414,22 @@ PS_OUTPUT main(PS_INPUT input, bool frontFace : SV_IsFrontFace)

# if defined(SKYLIGHTING)
float3 positionMSSkylight = input.WorldPosition.xyz;
# if defined(SKYLIGHTING_SHADOW_VIS)
float skylightingShadowVisibility = 1.0;
# endif
# if defined(DEFERRED)
sh2 skylightingSH = Skylighting::Sample(positionMSSkylight, worldNormal);
sh2 skylightingSH = Skylighting::Sample(positionMSSkylight, worldNormal
# if defined(SKYLIGHTING_SHADOW_VIS)
, skylightingShadowVisibility
# endif
);
# else
sh2 skylightingSH = inWorld ? Skylighting::Sample(positionMSSkylight, worldNormal) : Skylighting::UNIT_SH;
sh2 skylightingSH = inWorld ? Skylighting::Sample(positionMSSkylight, worldNormal
# if defined(SKYLIGHTING_SHADOW_VIS)
, skylightingShadowVisibility
# endif
) : Skylighting::UNIT_SH;
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# endif

# endif

float4 waterData = SharedData::GetWaterData(input.WorldPosition.xyz);
Expand Down Expand Up @@ -2561,22 +2577,28 @@ PS_OUTPUT main(PS_INPUT input, bool frontFace : SV_IsFrontFace)
float dirSoftShadow = 1.0;
float dirVSMDetailedShadow = 1.0;

# if defined(VOLUMETRIC_SHADOWS)
# if defined(VOLUMETRIC_SHADOWS) && !(defined(DEFERRED) && defined(SKYLIGHTING_SHADOW_VIS))
if (inWorld && !inReflection && ShadowSampling::HasDirectionalShadows())
dirSoftShadow = ShadowSampling::GetLightingShadow(input.WorldPosition.xyz, dirVSMDetailedShadow);
# if !defined(SKYLIGHTING_SHADOW_VIS)
dirSoftShadow =
# endif
ShadowSampling::GetLightingShadow(input.WorldPosition.xyz, dirVSMDetailedShadow);
# endif

float dirDetailedShadow = 1.0;

if ((Permutation::PixelShaderDescriptor & Permutation::LightingFlags::DefShadow) && (Permutation::PixelShaderDescriptor & Permutation::LightingFlags::ShadowDir)) {
dirDetailedShadow *= shadowColor.x;

# if !defined(VOLUMETRIC_SHADOWS)
# if !defined(VOLUMETRIC_SHADOWS) && !defined(SKYLIGHTING_SHADOW_VIS)
dirSoftShadow = dirDetailedShadow;
# endif
} else {
}
# if !defined(DEFERRED)
else {
dirDetailedShadow = dirVSMDetailedShadow;
}
# endif

# if defined(SCREEN_SPACE_SHADOWS) && defined(DEFERRED)
if (!SharedData::InInterior && dirLightAngle >= 0.0)
Expand Down Expand Up @@ -2626,6 +2648,10 @@ PS_OUTPUT main(PS_INPUT input, bool frontFace : SV_IsFrontFace)
}
# endif

# if defined(SKYLIGHTING_SHADOW_VIS)
dirSoftShadow = skylightingShadowVisibility;
# endif

float3 diffuseColor = 0.0.xxx;
float3 specularColor = 0.0.xxx;
float3 transmissionColor = 0.0.xxx;
Expand Down
6 changes: 4 additions & 2 deletions package/Shaders/RunGrass.hlsl
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Expand Up @@ -559,7 +559,8 @@ PS_OUTPUT main(PS_INPUT input, bool frontFace : SV_IsFrontFace)

# if defined(SKYLIGHTING)
float3 positionMSSkylight = input.WorldPosition.xyz;
float skylightingDiffuse = Skylighting::GetVertexSkylightingDiffuse(positionMSSkylight, normal, vertexAO);
sh2 skylightingSH = Skylighting::Sample(positionMSSkylight, normal);
float skylightingDiffuse = Skylighting::GetSkylightingDiffuse(skylightingSH, positionMSSkylight, normal, vertexAO);
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# endif // SKYLIGHTING

float3 albedo = baseColor.xyz * vertexColor;
Expand Down Expand Up @@ -820,7 +821,8 @@ PS_OUTPUT main(PS_INPUT input)

# if defined(SKYLIGHTING)
float3 positionMSSkylight = input.WorldPosition.xyz;
float skylightingDiffuse = Skylighting::GetVertexSkylightingDiffuse(positionMSSkylight, normal, vertexAO);
sh2 skylightingSH = Skylighting::Sample(positionMSSkylight, normal);
float skylightingDiffuse = Skylighting::GetSkylightingDiffuse(skylightingSH, positionMSSkylight, normal, vertexAO);
# endif // SKYLIGHTING

float3 directionalAmbientColor = Color::Ambient(max(0, SharedData::GetAmbient(normal)));
Expand Down
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