Add support for cascades to DDGI
This commit is contained in:
Wojciech Figat
@@ -22,19 +22,18 @@
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// DDGI data for a constant buffer
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struct DDGIData
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{
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float3 ProbesOrigin;
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float ProbesSpacing;
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float4 RaysRotation;
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float4 ProbesOriginAndSpacing[4];
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int4 ProbesScrollOffsets[4];
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int4 ProbeScrollDirections[4];
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uint3 ProbesCounts;
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uint CascadesCount;
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float IrradianceGamma;
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int3 ProbesScrollOffsets;
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float ProbeHistoryWeight;
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float RayMaxDistance;
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float Padding0;
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float4 RaysRotation;
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float3 ViewDir;
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uint RaysCount;
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int3 ProbeScrollDirections;
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float RayMaxDistance;
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uint3 ProbeScrollClear; // TODO: pack into bits
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uint Padding0;
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};
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uint GetDDGIProbeIndex(DDGIData data, uint3 probeCoords)
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@@ -62,88 +61,106 @@ uint3 GetDDGIProbeCoords(DDGIData data, uint probeIndex)
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return probeCoords;
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}
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uint2 GetDDGIProbeTexelCoords(DDGIData data, uint probeIndex)
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uint2 GetDDGIProbeTexelCoords(DDGIData data, uint cascadeIndex, uint probeIndex)
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{
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uint probesPerPlane = data.ProbesCounts.x * data.ProbesCounts.z;
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uint planeIndex = probeIndex / probesPerPlane;
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uint gridSpaceX = probeIndex % data.ProbesCounts.x;
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uint gridSpaceY = probeIndex / data.ProbesCounts.x;
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uint x = gridSpaceX + (planeIndex * data.ProbesCounts.x);
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uint y = gridSpaceY % data.ProbesCounts.z;
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uint y = gridSpaceY % data.ProbesCounts.z + cascadeIndex * data.ProbesCounts.z;
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return uint2(x, y);
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}
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uint GetDDGIScrollingProbeIndex(DDGIData data, uint3 probeCoords)
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uint GetDDGIScrollingProbeIndex(DDGIData data, uint cascadeIndex, uint3 probeCoords)
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{
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// Probes are scrolled on edges to stabilize GI when camera moves
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return GetDDGIProbeIndex(data, (probeCoords + data.ProbesScrollOffsets + data.ProbesCounts) % data.ProbesCounts);
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return GetDDGIProbeIndex(data, (probeCoords + data.ProbesScrollOffsets[cascadeIndex].xyz + data.ProbesCounts) % data.ProbesCounts);
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}
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float3 GetDDGIProbeWorldPosition(DDGIData data, uint3 probeCoords)
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float3 GetDDGIProbeWorldPosition(DDGIData data, uint cascadeIndex, uint3 probeCoords)
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{
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float3 probePosition = probeCoords * data.ProbesSpacing;
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float3 probeGridOffset = (data.ProbesSpacing * (data.ProbesCounts - 1)) * 0.5f;
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return data.ProbesOrigin + probePosition - probeGridOffset + (data.ProbesScrollOffsets * data.ProbesSpacing);
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float3 probesOrigin = data.ProbesOriginAndSpacing[cascadeIndex].xyz;
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float probesSpacing = data.ProbesOriginAndSpacing[cascadeIndex].w;
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float3 probePosition = probeCoords * probesSpacing;
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float3 probeGridOffset = (probesSpacing * (data.ProbesCounts - 1)) * 0.5f;
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return probesOrigin + probePosition - probeGridOffset + (data.ProbesScrollOffsets[cascadeIndex].xyz * probesSpacing);
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}
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// Loads probe probe state
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float LoadDDGIProbeState(DDGIData data, Texture2D<float4> probesState, uint probeIndex)
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float LoadDDGIProbeState(DDGIData data, Texture2D<float4> probesState, uint cascadeIndex, uint probeIndex)
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{
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int2 probeDataCoords = GetDDGIProbeTexelCoords(data, probeIndex);
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int2 probeDataCoords = GetDDGIProbeTexelCoords(data, cascadeIndex, probeIndex);
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float4 probeState = probesState.Load(int3(probeDataCoords, 0));
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return probeState.w;
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}
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// Loads probe world-space position (XYZ) and probe state (W)
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float4 LoadDDGIProbePositionAndState(DDGIData data, Texture2D<float4> probesState, uint probeIndex, uint3 probeCoords)
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float4 LoadDDGIProbePositionAndState(DDGIData data, Texture2D<float4> probesState, uint cascadeIndex, uint probeIndex, uint3 probeCoords)
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{
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int2 probeDataCoords = GetDDGIProbeTexelCoords(data, probeIndex);
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int2 probeDataCoords = GetDDGIProbeTexelCoords(data, cascadeIndex, probeIndex);
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float4 probeState = probesState.Load(int3(probeDataCoords, 0));
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probeState.xyz += GetDDGIProbeWorldPosition(data, probeCoords);
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probeState.xyz += GetDDGIProbeWorldPosition(data, cascadeIndex, probeCoords);
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return probeState;
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}
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// Calculates texture UVs for sampling probes atlas texture (irradiance or distance)
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float2 GetDDGIProbeUV(DDGIData data, uint probeIndex, float2 octahedralCoords, uint resolution)
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float2 GetDDGIProbeUV(DDGIData data, uint cascadeIndex, uint probeIndex, float2 octahedralCoords, uint resolution)
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{
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uint2 coords = GetDDGIProbeTexelCoords(data, probeIndex);
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uint2 coords = GetDDGIProbeTexelCoords(data, cascadeIndex, probeIndex);
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float probeTexelSize = resolution + 2.0f;
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float textureWidth = probeTexelSize * (data.ProbesCounts.x * data.ProbesCounts.y);
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float textureHeight = probeTexelSize * data.ProbesCounts.z;
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float2 textureSize = float2(data.ProbesCounts.x * data.ProbesCounts.y, data.ProbesCounts.z * data.CascadesCount) * probeTexelSize;
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float2 uv = float2(coords.x * probeTexelSize, coords.y * probeTexelSize) + (probeTexelSize * 0.5f);
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uv += octahedralCoords.xy * (resolution * 0.5f);
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uv /= float2(textureWidth, textureHeight);
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uv /= textureSize;
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return uv;
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}
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// Samples DDGI probes volume at the given world-space position and returns the irradiance.
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float3 SampleDDGIIrradiance(DDGIData data, Texture2D<float4> probesState, Texture2D<float4> probesDistance, Texture2D<float4> probesIrradiance, float3 worldPosition, float3 worldNormal, float bias)
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// rand - randomized per-pixel value in range 0-1, used to smooth dithering for cascades blending
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float3 SampleDDGIIrradiance(DDGIData data, Texture2D<float4> probesState, Texture2D<float4> probesDistance, Texture2D<float4> probesIrradiance, float3 worldPosition, float3 worldNormal, float bias, float dither = 0.0f)
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{
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float4 irradiance = float4(0, 0, 0, 0);
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float3 probesOrigin = data.ProbesScrollOffsets * data.ProbesSpacing + data.ProbesOrigin;
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float3 probesExtent = (data.ProbesCounts - 1) * (data.ProbesSpacing * 0.5f);
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// Select the highest cascade that contains the sample location
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uint cascadeIndex = 0;
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for (; cascadeIndex < data.CascadesCount; cascadeIndex++)
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{
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float probesSpacing = data.ProbesOriginAndSpacing[cascadeIndex].w;
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float3 probesOrigin = data.ProbesScrollOffsets[cascadeIndex].xyz * probesSpacing + data.ProbesOriginAndSpacing[cascadeIndex].xyz;
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float3 probesExtent = (data.ProbesCounts - 1) * (probesSpacing * 0.5f);
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float fadeDistance = probesSpacing * 0.5f;
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float cascadeWeight = saturate(Min3(probesExtent - abs(worldPosition - probesOrigin)) / fadeDistance);
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if (cascadeWeight > dither) // Use dither to make transition smoother
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break;
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}
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if (cascadeIndex == data.CascadesCount)
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return float3(0, 0, 0);
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float probesSpacing = data.ProbesOriginAndSpacing[cascadeIndex].w;
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float3 probesOrigin = data.ProbesScrollOffsets[cascadeIndex].xyz * probesSpacing + data.ProbesOriginAndSpacing[cascadeIndex].xyz;
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float3 probesExtent = (data.ProbesCounts - 1) * (probesSpacing * 0.5f);
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// Bias the world-space position to reduce artifacts
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float3 surfaceBias = (worldNormal * bias) + (data.ViewDir * (bias * -4.0f));
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float3 biasedWorldPosition = worldPosition + surfaceBias;
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// Get the grid coordinates of the probe nearest the biased world position
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uint3 baseProbeCoords = clamp(uint3((worldPosition - probesOrigin + probesExtent) / data.ProbesSpacing), 0, data.ProbesCounts - 1);
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float3 baseProbeWorldPosition = GetDDGIProbeWorldPosition(data, baseProbeCoords);
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float3 biasAlpha = saturate((biasedWorldPosition - baseProbeWorldPosition) / data.ProbesSpacing);
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uint3 baseProbeCoords = clamp(uint3((worldPosition - probesOrigin + probesExtent) / probesSpacing), 0, data.ProbesCounts - 1);
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float3 baseProbeWorldPosition = GetDDGIProbeWorldPosition(data, cascadeIndex, baseProbeCoords);
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float3 biasAlpha = saturate((biasedWorldPosition - baseProbeWorldPosition) / probesSpacing);
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// Loop over the closest probes to accumulate their contributions
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float4 irradiance = float4(0, 0, 0, 0);
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for (uint i = 0; i < 8; i++)
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{
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uint3 probeCoordsOffset = uint3(i, i >> 1, i >> 2) & 1;
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uint3 probeCoords = clamp(baseProbeCoords + probeCoordsOffset, 0, data.ProbesCounts - 1);
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uint probeIndex = GetDDGIScrollingProbeIndex(data, probeCoords);
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uint probeIndex = GetDDGIScrollingProbeIndex(data, cascadeIndex, probeCoords);
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// Load probe position and state
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float4 probeState = probesState.Load(int3(GetDDGIProbeTexelCoords(data, probeIndex), 0));
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float4 probeState = probesState.Load(int3(GetDDGIProbeTexelCoords(data, cascadeIndex, probeIndex), 0));
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if (probeState.w == DDGI_PROBE_STATE_INACTIVE)
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continue;
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float3 probeBasePosition = baseProbeWorldPosition + ((probeCoords - baseProbeCoords) * data.ProbesSpacing);
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float3 probeBasePosition = baseProbeWorldPosition + ((probeCoords - baseProbeCoords) * probesSpacing);
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float3 probePosition = probeBasePosition + probeState.xyz;
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// Calculate the distance and direction from the (biased and non-biased) shading point and the probe
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@@ -156,7 +173,7 @@ float3 SampleDDGIIrradiance(DDGIData data, Texture2D<float4> probesState, Textur
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// Sample distance texture
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float2 octahedralCoords = GetOctahedralCoords(-biasedPosToProbe);
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float2 uv = GetDDGIProbeUV(data, probeIndex, octahedralCoords, DDGI_PROBE_RESOLUTION_DISTANCE);
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float2 uv = GetDDGIProbeUV(data, cascadeIndex, probeIndex, octahedralCoords, DDGI_PROBE_RESOLUTION_DISTANCE);
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float2 probeDistance = probesDistance.SampleLevel(SamplerLinearClamp, uv, 0).rg * 2.0f;
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float probeDistanceMean = probeDistance.x;
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float probeDistanceMean2 = probeDistance.y;
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@@ -183,7 +200,7 @@ float3 SampleDDGIIrradiance(DDGIData data, Texture2D<float4> probesState, Textur
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// Sample irradiance texture
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octahedralCoords = GetOctahedralCoords(worldNormal);
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uv = GetDDGIProbeUV(data, probeIndex, octahedralCoords, DDGI_PROBE_RESOLUTION_IRRADIANCE);
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uv = GetDDGIProbeUV(data, cascadeIndex, probeIndex, octahedralCoords, DDGI_PROBE_RESOLUTION_IRRADIANCE);
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float3 probeIrradiance = probesIrradiance.SampleLevel(SamplerLinearClamp, uv, 0).rgb;
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#if DDGI_SRGB_BLENDING
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probeIrradiance = pow(probeIrradiance, data.IrradianceGamma * 0.5f);
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@@ -196,6 +213,18 @@ float3 SampleDDGIIrradiance(DDGIData data, Texture2D<float4> probesState, Textur
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irradiance += float4(probeIrradiance * weight, weight);
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}
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#if 0
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// Debug DDGI cascades with colors
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if (cascadeIndex == 0)
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irradiance = float4(1, 0, 0, 1);
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else if (cascadeIndex == 1)
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irradiance = float4(0, 1, 0, 1);
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else if (cascadeIndex == 2)
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irradiance = float4(0, 0, 1, 1);
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else
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irradiance = float4(1, 0, 1, 1);
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#endif
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if (irradiance.a > 0.0f)
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{
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// Normalize irradiance
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@@ -204,10 +233,6 @@ float3 SampleDDGIIrradiance(DDGIData data, Texture2D<float4> probesState, Textur
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irradiance.rgb *= irradiance.rgb;
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#endif
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irradiance.rgb *= 2.0f * PI;
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// Fade-out outside the probes volume
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float fadeDistance = data.ProbesSpacing * 0.5f;
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irradiance.rgb *= saturate(Min3(probesExtent - abs(worldPosition - probesOrigin)) / fadeDistance);
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}
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return irradiance.rgb;
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}
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