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Refactor DDGI irradiance filtering for smoother and more accurate lighting

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This commit is contained in:
Wojtek Figat
2025-12-31 00:19:51 +01:00
parent ce45fa3d54
commit 37df16a3e4
2 changed files with 17 additions and 11 deletions
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21
Source/Shaders/GI/DDGI.hlsl
View File

@@ -25,6 +25,7 @@
#define DDGI_CASCADE_BLEND_SMOOTH 0 // Enables smooth cascade blending, otherwise dithering will be used
#endif
#define DDGI_SRGB_BLENDING 1 // Enables blending in sRGB color space, otherwise irradiance blending is done in linear space
#define DDGI_DEFAULT_BIAS 0.2f // Default value for DDGI sampling bias
// DDGI data for a constant buffer
struct DDGIData
@@ -181,13 +182,14 @@ float3 SampleDDGIIrradianceCascade(DDGIData data, Texture2D<snorm float4> probes
if (probeState == DDGI_PROBE_STATE_INACTIVE)
{
// Search nearby probes to find any nearby GI sample
LOOP
for (int searchDistance = 1; searchDistance < 3 && probeState == DDGI_PROBE_STATE_INACTIVE; searchDistance++)
{
for (uint searchAxis = 0; searchAxis < 3; searchAxis++)
{
int searchAxisSign = probeCoordsOffset[searchAxis] ? 1 : -1;
int3 searchCoordsOffset = SearchAxes[searchAxis] * (searchAxisSign * searchDistance);
uint3 searchCoords = clamp((int3)probeCoords + searchCoordsOffset, int3(0, 0, 0), (int3)probeCoordsEnd);
uint3 searchCoords = clamp((uint3)((int3)probeCoords + searchCoordsOffset), uint3(0, 0, 0), probeCoordsEnd);
uint searchIndex = GetDDGIScrollingProbeIndex(data, cascadeIndex, searchCoords);
float4 searchData = LoadDDGIProbeData(data, probesData, cascadeIndex, searchIndex);
uint searchState = DecodeDDGIProbeState(searchData);
@@ -205,8 +207,9 @@ float3 SampleDDGIIrradianceCascade(DDGIData data, Texture2D<snorm float4> probes
if (probeState == DDGI_PROBE_STATE_INACTIVE)
continue;
}
float3 probeBasePosition = baseProbeWorldPosition + ((probeCoords - baseProbeCoords) * probesSpacing);
float3 probePosition = probeBasePosition + probeData.xyz * probesSpacing; // Probe offset is [-1;1] within probes spacing
// Calculate probe position
float3 probePosition = baseProbeWorldPosition + (((float3)probeCoords - (float3)baseProbeCoords) * probesSpacing) + probeData.xyz * probesSpacing;
// Calculate the distance and direction from the (biased and non-biased) shading point and the probe
float3 worldPosToProbe = normalize(probePosition - worldPosition);
@@ -215,6 +218,7 @@ float3 SampleDDGIIrradianceCascade(DDGIData data, Texture2D<snorm float4> probes
// Smooth backface test
float weight = Square(dot(worldPosToProbe, worldNormal) * 0.5f + 0.5f);
weight = max(weight, 0.1f);
// Sample distance texture
float2 octahedralCoords = GetOctahedralCoords(-biasedPosToProbe);
@@ -226,7 +230,7 @@ float3 SampleDDGIIrradianceCascade(DDGIData data, Texture2D<snorm float4> probes
{
float variance = abs(Square(probeDistance.x) - probeDistance.y);
float visibilityWeight = variance / (variance + Square(biasedPosToProbeDist - probeDistance.x));
weight *= max(visibilityWeight * visibilityWeight * visibilityWeight, 0.05f);
weight *= max(visibilityWeight * visibilityWeight * visibilityWeight, 0.0f);
}
// Avoid a weight of zero
@@ -238,7 +242,7 @@ float3 SampleDDGIIrradianceCascade(DDGIData data, Texture2D<snorm float4> probes
// Calculate trilinear weights based on the distance to each probe to smoothly transition between grid of 8 probes
float3 trilinear = lerp(1.0f - biasAlpha, biasAlpha, (float3)probeCoordsOffset);
weight *= max(trilinear.x * trilinear.y * trilinear.z, 0.001f);
weight *= saturate(trilinear.x * trilinear.y * trilinear.z * 2.0f);
// Sample irradiance texture
octahedralCoords = GetOctahedralCoords(worldNormal);
@@ -270,7 +274,8 @@ float3 SampleDDGIIrradianceCascade(DDGIData data, Texture2D<snorm float4> probes
if (irradiance.a > 0.0f)
{
// Normalize irradiance
irradiance.rgb /= irradiance.a;
//irradiance.rgb /= irradiance.a;
irradiance.rgb /= lerp(1, irradiance.a, saturate(irradiance.a * irradiance.a + 0.9f));
#if DDGI_SRGB_BLENDING
irradiance.rgb *= irradiance.rgb;
#endif
@@ -282,13 +287,13 @@ float3 SampleDDGIIrradianceCascade(DDGIData data, Texture2D<snorm float4> probes
float3 GetDDGISurfaceBias(float3 viewDir, float probesSpacing, float3 worldNormal, float bias)
{
// Bias the world-space position to reduce artifacts
return (worldNormal * 0.2f + viewDir * 0.8f) * (0.75f * probesSpacing * bias);
return (worldNormal * 0.2f + viewDir * 0.8f) * (0.6f * probesSpacing * bias);
}
// Samples DDGI probes volume at the given world-space position and returns the irradiance.
// bias - scales the bias vector to the initial sample point to reduce self-shading artifacts
// dither - randomized per-pixel value in range 0-1, used to smooth dithering for cascades blending
float3 SampleDDGIIrradiance(DDGIData data, Texture2D<snorm float4> probesData, Texture2D<float4> probesDistance, Texture2D<float4> probesIrradiance, float3 worldPosition, float3 worldNormal, float bias = 0.2f, float dither = 0.0f)
float3 SampleDDGIIrradiance(DDGIData data, Texture2D<snorm float4> probesData, Texture2D<float4> probesDistance, Texture2D<float4> probesIrradiance, float3 worldPosition, float3 worldNormal, float bias = DDGI_DEFAULT_BIAS, float dither = 0.0f)
{
// Select the highest cascade that contains the sample location
uint cascadeIndex = 0;

7
Source/Shaders/GI/DDGI.shader
View File

@@ -395,6 +395,8 @@ void CS_TraceRays(uint3 DispatchThreadId : SV_DispatchThreadID)
// Add some bias to prevent self occlusion artifacts in Chebyshev due to Global SDF being very incorrect in small scale
radiance.w = max(radiance.w + GlobalSDF.CascadeVoxelSize[hit.HitCascade] * 0.5f, 0);
float probesSpacing = DDGI.ProbesOriginAndSpacing[CascadeIndex].w;
radiance.w += probesSpacing * 0.05f;
}
}
else
@@ -793,10 +795,9 @@ void PS_IndirectLighting(Quad_VS2PS input, out float4 output : SV_Target0)
}
// Sample irradiance
float bias = 0.2f;
float dither = RandN2(input.TexCoord + TemporalTime).x;
float3 irradiance = SampleDDGIIrradiance(DDGI, ProbesData, ProbesDistance, ProbesIrradiance, gBuffer.WorldPos, gBuffer.Normal, bias, dither);
float3 irradiance = SampleDDGIIrradiance(DDGI, ProbesData, ProbesDistance, ProbesIrradiance, gBuffer.WorldPos, gBuffer.Normal, DDGI_DEFAULT_BIAS, dither);
// Calculate lighting
float3 diffuseColor = GetDiffuseColor(gBuffer);
float3 diffuse = Diffuse_Lambert(diffuseColor);