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Add view snapping mode to Directional Light shadows for better stability

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This commit is contained in:
Wojtek Figat
2021-07-12 11:25:10 +02:00
parent 716b726589
commit 0a47477290
1 changed files with 27 additions and 11 deletions
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38
Source/Engine/Renderer/ShadowsPass.cpp
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@@ -566,6 +566,7 @@ void ShadowsPass::RenderShadow(RenderContext& renderContext, RendererDirectional
}
// Select best Up vector
Vector3 side = Vector3::UnitX;
Vector3 upDirection = Vector3::UnitX;
Vector3 VectorUps[] = { Vector3::UnitY, Vector3::UnitX, Vector3::UnitZ };
for (int32 i = 0; i < ARRAY_COUNT(VectorUps); i++)
@@ -573,7 +574,7 @@ void ShadowsPass::RenderShadow(RenderContext& renderContext, RendererDirectional
const Vector3 vectorUp = VectorUps[i];
if (Math::Abs(Vector3::Dot(lightDirection, vectorUp)) < (1.0f - 0.0001f))
{
const Vector3 side = Vector3::Normalize(Vector3::Cross(vectorUp, lightDirection));
side = Vector3::Normalize(Vector3::Cross(vectorUp, lightDirection));
upDirection = Vector3::Normalize(Vector3::Cross(lightDirection, side));
break;
}
@@ -601,17 +602,22 @@ void ShadowsPass::RenderShadow(RenderContext& renderContext, RendererDirectional
// Calculate cascade split frustum corners in view space
for (int32 j = 0; j < 4; j++)
{
// Calculate frustum in WS and VS
float overlap = 0;
if (blendCSM)
overlap = 0.2f * (splitMinRatio - oldSplitMinRatio);
const auto frustumRangeVS = mainCache->FrustumCornersVs[j + 4] - mainCache->FrustumCornersVs[j];
frustumCorners[j] = mainCache->FrustumCornersVs[j] + frustumRangeVS * (splitMinRatio - overlap);
frustumCorners[j + 4] = mainCache->FrustumCornersVs[j] + frustumRangeVS * splitMaxRatio;
}
// Perform stabilization (using Projection Snapping)
// Perform stabilization
enum StabilizationMode
{
None,
ProjectionSnapping,
ViewSnapping,
};
const StabilizationMode stabilization = ViewSnapping; // TODO: expose to graphics settings maybe
Vector3 cascadeMinBoundLS;
Vector3 cascadeMaxBoundLS;
Vector3 target;
@@ -622,12 +628,21 @@ void ShadowsPass::RenderShadow(RenderContext& renderContext, RendererDirectional
// Compute bounding box center
Vector3::TransformCoordinate(boundingVS.Center, view.IV, target);
cascadeMaxBoundLS = Vector3(boundingVS.Radius);
cascadeMinBoundLS = -cascadeMaxBoundLS;
if (stabilization == ViewSnapping)
{
// Snap the target to the texel units (reference: ShaderX7 - Practical Cascaded Shadows Maps)
float shadowMapHalfSize = shadowMapsSizeCSM * 0.5f;
float x = Math::Ceil(Vector3::Dot(target, upDirection) * shadowMapHalfSize / boundingVS.Radius) * boundingVS.Radius / shadowMapHalfSize;
float y = Math::Ceil(Vector3::Dot(target, side) * shadowMapHalfSize / boundingVS.Radius) * boundingVS.Radius / shadowMapHalfSize;
float z = Vector3::Dot(target, lightDirection);
target = upDirection * x + side * y + lightDirection * z;
}
}
const auto nearClip = -2000.0f;
const auto nearClip = 0.0f;
const auto farClip = cascadeMaxBoundLS.Z - cascadeMinBoundLS.Z;
// Create shadow view matrix
@@ -636,7 +651,8 @@ void ShadowsPass::RenderShadow(RenderContext& renderContext, RendererDirectional
// Create viewport for culling with extended near/far planes due to culling issues
Matrix cullingVP;
{
Matrix::OrthoOffCenter(cascadeMinBoundLS.X, cascadeMaxBoundLS.X, cascadeMinBoundLS.Y, cascadeMaxBoundLS.Y, -100000.0f, farClip + 100000.0f, shadowProjection);
const float cullRangeExtent = 100000.0f;
Matrix::OrthoOffCenter(cascadeMinBoundLS.X, cascadeMaxBoundLS.X, cascadeMinBoundLS.Y, cascadeMaxBoundLS.Y, -cullRangeExtent, farClip + cullRangeExtent, shadowProjection);
Matrix::Multiply(shadowView, shadowProjection, cullingVP);
}
@@ -647,12 +663,12 @@ void ShadowsPass::RenderShadow(RenderContext& renderContext, RendererDirectional
Matrix::Multiply(shadowView, shadowProjection, shadowVP);
// Stabilize the shadow matrix on the projection
if (stabilization == ProjectionSnapping)
{
auto shadowPixelPosition = shadowVP.GetTranslation() * (shadowMapsSizeCSM * 0.5f);
Vector3 shadowPixelPosition = shadowVP.GetTranslation() * (shadowMapsSizeCSM * 0.5f);
shadowPixelPosition.Z = 0;
const auto shadowPixelPositionRounded = Vector3(Math::Round(shadowPixelPosition.X), Math::Round(shadowPixelPosition.Y), 0.0f);
auto shadowPixelOffset = Vector4(shadowPixelPositionRounded - shadowPixelPosition, 0.0f);
shadowPixelOffset *= 2.0f / shadowMapsSizeCSM;
const Vector3 shadowPixelPositionRounded(Math::Round(shadowPixelPosition.X), Math::Round(shadowPixelPosition.Y), 0.0f);
const Vector4 shadowPixelOffset((shadowPixelPositionRounded - shadowPixelPosition) * (2.0f / shadowMapsSizeCSM), 0.0f);
shadowProjection.SetRow4(shadowProjection.GetRow4() + shadowPixelOffset);
Matrix::Multiply(shadowView, shadowProjection, shadowVP);
}