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Fix directional light cascaded shadow maps rendering stability

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This commit is contained in:
Wojciech Figat
2026-05-04 08:46:43 +02:00
parent 7a569d4f14
commit 83de99877c
1 changed files with 36 additions and 28 deletions
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Source/Engine/Renderer/ShadowsPass.cpp
+36 -28
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@@ -370,6 +370,7 @@ public:
void DirtyStaticBounds(const BoundingSphere& bounds)
{
PROFILE_CPU();
// TODO: use octree to improve bounds-testing
// TODO: build list of modified bounds and dirty them in batch on next frame start (ideally in async within shadows setup job)
for (auto& e : Lights)
@@ -773,7 +774,6 @@ void ShadowsPass::SetupLight(ShadowsCustomBuffer& shadows, RenderContext& render
{
SetupLight(shadows, renderContext, renderContextBatch, (RenderLightData&)light, atlasLight);
const RenderView& view = renderContext.View;
const int32 csmCount = atlasLight.TilesCount;
const auto shadowMapsSize = (float)atlasLight.Resolution;
atlasLight.BlendCSM = Graphics::AllowCSMBlending;
@@ -787,9 +787,9 @@ void ShadowsPass::SetupLight(ShadowsCustomBuffer& shadows, RenderContext& render
#endif
// Calculate cascade splits
const float minDistance = view.Near;
const float maxDistance = view.Near + atlasLight.Distance;
const float viewRange = view.Far - view.Near;
const float minDistance = renderContext.View.Near;
const float maxDistance = renderContext.View.Near + atlasLight.Distance;
const float viewRange = renderContext.View.Far - renderContext.View.Near;
float cascadeSplits[MAX_CSM_CASCADES];
{
PartitionMode partitionMode = light.PartitionMode;
@@ -843,9 +843,9 @@ void ShadowsPass::SetupLight(ShadowsCustomBuffer& shadows, RenderContext& render
// Convert distance splits to ratios cascade in the range [0, 1]
for (int32 i = 0; i < MAX_CSM_CASCADES; i++)
cascadeSplits[i] = (cascadeSplits[i] - view.Near) / viewRange;
cascadeSplits[i] = (cascadeSplits[i] - renderContext.View.Near) / viewRange;
}
atlasLight.CascadeSplits = view.Near + Float4(cascadeSplits) * viewRange;
atlasLight.CascadeSplits = renderContext.View.Near + Float4(cascadeSplits) * viewRange;
// Update cached state (invalidate it if the light changed)
atlasLight.ValidateCache(renderContext.View, light);
@@ -881,21 +881,29 @@ void ShadowsPass::SetupLight(ShadowsCustomBuffer& shadows, RenderContext& render
renderContextBatch.Contexts.AddDefault(atlasLight.ContextCount);
atlasLight.Cache.Set(renderContext.View, light, atlasLight.CascadeSplits);
// Calculate view frustum corners (un-jittered) in view-space
Float3 frustumCorners[8];
// Get the 8 points of the view frustum in view-space (unproject from clip-space)
Float3 frustumCornersVs[8];
{
BoundingFrustum stableViewFrustum;
Matrix m;
Matrix::Multiply(renderContext.View.View, renderContext.View.NonJitteredProjection, m);
stableViewFrustum.SetMatrix(m);
stableViewFrustum.GetCorners(frustumCorners);
Float3 frustumCornersCs[8] =
{
Float3(-1.0f, 1.0f, 0.0f),
Float3(1.0f, 1.0f, 0.0f),
Float3(1.0f, -1.0f, 0.0f),
Float3(-1.0f, -1.0f, 0.0f),
Float3(-1.0f, 1.0f, 1.0f),
Float3(1.0f, 1.0f, 1.0f),
Float3(1.0f, -1.0f, 1.0f),
Float3(-1.0f, -1.0f, 1.0f),
};
Matrix invProjectionMatrix;
Matrix::Invert(renderContext.View.NonJitteredProjection, invProjectionMatrix);
for (int32 i = 0; i < 8; i++)
Float3::TransformCoordinate(frustumCornersCs[i], invProjectionMatrix, frustumCornersVs[i]);
}
for (int32 i = 0; i < 8; i++)
Float3::Transform(frustumCorners[i], renderContext.View.View, frustumCorners[i]);
// Create the different view and projection matrices for each split
float splitMinRatio = 0;
float splitMaxRatio = (minDistance - view.Near) / viewRange;
float splitMaxRatio = (minDistance - renderContext.View.Near) / viewRange;
int32 contextIndex = 0;
for (int32 cascadeIndex = 0; cascadeIndex < csmCount; cascadeIndex++)
{
@@ -908,31 +916,31 @@ void ShadowsPass::SetupLight(ShadowsCustomBuffer& shadows, RenderContext& render
continue;
// Calculate cascade split frustum corners in view space
Float3 frustumCornersVs[8];
Float3 cascadeCornersVs[8];
float csmOverlap = atlasLight.BlendCSM ? 0.2f : 0.1f;
for (int32 j = 0; j < 4; j++)
{
float csmOverlap = atlasLight.BlendCSM ? 0.2f : 0.1f;
float overlapWithPrevSplit = csmOverlap * (splitMinRatio - oldSplitMinRatio);
const auto frustumRangeVS = frustumCorners[j + 4] - frustumCorners[j];
frustumCornersVs[j] = frustumCorners[j] + frustumRangeVS * (splitMinRatio - overlapWithPrevSplit);
frustumCornersVs[j + 4] = frustumCorners[j] + frustumRangeVS * splitMaxRatio;
const Float3 frustumRangeVS = frustumCornersVs[j + 4] - frustumCornersVs[j];
cascadeCornersVs[j] = frustumCornersVs[j] + frustumRangeVS * (splitMinRatio - overlapWithPrevSplit);
cascadeCornersVs[j + 4] = frustumCornersVs[j] + frustumRangeVS * splitMaxRatio;
}
// Transform the frustum from camera view space to world-space
Float3 frustumCornersWs[8];
Float3 cascadeCornersWs[8];
for (int32 i = 0; i < 8; i++)
Float3::Transform(frustumCornersVs[i], renderContext.View.IV, frustumCornersWs[i]);
Float3::Transform(cascadeCornersVs[i], renderContext.View.IV, cascadeCornersWs[i]);
// Calculate the centroid of the view frustum slice
Float3 frustumCenter = Float3::Zero;
for (int32 i = 0; i < 8; i++)
frustumCenter += frustumCornersWs[i];
frustumCenter += cascadeCornersWs[i];
frustumCenter *= 1.0f / 8.0f;
// Calculate the radius of a bounding sphere surrounding the frustum corners
float frustumRadius = 0.0f;
for (int32 i = 0; i < 8; i++)
frustumRadius = Math::Max(frustumRadius, (frustumCornersWs[i] - frustumCenter).LengthSquared());
frustumRadius = Math::Max(frustumRadius, (cascadeCornersWs[i] - frustumCenter).LengthSquared());
frustumRadius = Math::Ceil(Math::Sqrt(frustumRadius) * 16.0f) / 16.0f;
// Snap cascade center to the texel size
@@ -955,7 +963,7 @@ void ShadowsPass::SetupLight(ShadowsCustomBuffer& shadows, RenderContext& render
Matrix::LookAt(frustumCenter + light.Direction * minExtents.Z, frustumCenter, up, shadowView);
// Create viewport for culling with extended near/far planes due to culling issues (aka pancaking)
const float cullRangeExtent = 100000.0f;
const float cullRangeExtent = METERS_TO_UNITS(1000.0f);
Matrix::OrthoOffCenter(minExtents.X, maxExtents.X, minExtents.Y, maxExtents.Y, -cullRangeExtent, cascadeExtents.Z + cullRangeExtent, shadowProjection);
Matrix::Multiply(shadowView, shadowProjection, cullingVP);
@@ -981,11 +989,11 @@ void ShadowsPass::SetupLight(ShadowsCustomBuffer& shadows, RenderContext& render
// Setup context for cascade
auto& shadowContext = renderContextBatch.Contexts[atlasLight.ContextIndex + contextIndex++];
SetupRenderContext(renderContext, shadowContext);
shadowContext.View.Position = light.Direction * -atlasLight.Distance + view.Position;
shadowContext.View.Position = light.Direction * -atlasLight.Distance + renderContext.View.Position;
shadowContext.View.Direction = light.Direction;
shadowContext.View.SetUp(shadowView, shadowProjection);
shadowContext.View.CullingFrustum.SetMatrix(cullingVP);
shadowContext.View.PrepareCache(shadowContext, shadowMapsSize, shadowMapsSize, Float2::Zero, &view);
shadowContext.View.PrepareCache(shadowContext, shadowMapsSize, shadowMapsSize, Float2::Zero, &renderContext.View);
}
}