file
function     void FLightmassExporter::WriteSceneSettings

		VERIFYLIGHTMASSINI(GConfig->GetFloat(TEXT("DevOptions.StaticLightingSceneConstants"), TEXT("VisibilityNormalOffsetDistance"), Scene.SceneConstants.VisibilityNormalOffsetDistance, GLightmassIni));
		VERIFYLIGHTMASSINI(GConfig->GetFloat(TEXT("DevOptions.StaticLightingSceneConstants"), TEXT("VisibilityNormalOffsetSampleRadiusScale"), Scene.SceneConstants.VisibilityNormalOffsetSampleRadiusScale, GLightmassIni));
		VERIFYLIGHTMASSINI(GConfig->GetFloat(TEXT("DevOptions.StaticLightingSceneConstants"), TEXT("VisibilityTangentOffsetSampleRadiusScale"), Scene.SceneConstants.VisibilityTangentOffsetSampleRadiusScale, GLightmassIni));
		VERIFYLIGHTMASSINI(GConfig->GetFloat(TEXT("DevOptions.StaticLightingSceneConstants"), TEXT("SmallestTexelRadius"), Scene.SceneConstants.SmallestTexelRadius, GLightmassIni));
		VERIFYLIGHTMASSINI(GConfig->GetInt(TEXT("DevOptions.StaticLightingSceneConstants"), TEXT("LightGridSize"), Scene.SceneConstants.LightGridSize, GLightmassIni));
	}
	{
		VERIFYLIGHTMASSINI(GConfig->GetBool(TEXT("DevOptions.StaticLightingMaterial"), TEXT("bUseDebugMaterial"), bConfigBool, GLightmassIni));
		Scene.MaterialSettings.bUseDebugMaterial = bConfigBool;

file
namespace    Lightmass
function     void FStaticLightingSystem::IntersectLightRays

			// Offset the sample's starting point in the tangent XY plane based on the sample's area of influence. 
			// This is particularly effective for large texels with high variance in the incoming radiance over the area of the texel.
			SampleOffset = Vertex.WorldTangentX * TangentPathDirection.X * SampleRadius * SceneConstants.VisibilityTangentOffsetSampleRadiusScale
				+ Vertex.WorldTangentY * TangentPathDirection.Y * SampleRadius * SceneConstants.VisibilityTangentOffsetSampleRadiusScale;
			
			// Experiment to distribute the starting position over the area of the texel to anti-alias, causes incorrect shadowing at intersections though
			//@todo - use consistent sample set between irradiance cache samples
			//const FVector2f DiskPosition = GetUniformUnitDiskPosition(RandomStream);
			//SampleOffset = Vertex.WorldTangentX * DiskPosition.X * SampleRadius * .5f + Vertex.WorldTangentY * DiskPosition.Y * SampleRadius * .5f;
		}

file
namespace    Lightmass
function     void FStaticLightingSystem::IntersectLightRays

		const float RayStartNormalBiasScale = RayBiasMode == RBM_ConstantNormalOffset
			? SceneConstants.VisibilityNormalOffsetSampleRadiusScale 
			: (SceneConstants.VisibilityTangentOffsetSampleRadiusScale * TangentPathDirection.Z);

		// Apply various offsets to the start of the ray.
		// The offset along the ray direction is to avoid incorrect self-intersection due to floating point precision.
		// The offset along the normal is to push self-intersection patterns (like triangle shape) on highly curved surfaces onto the backfaces.
		FVector3f RayStart = Vertex.WorldPosition
			+ WorldPathDirection * SceneConstants.VisibilityRayOffsetDistance

						// Vector from the center to one of the corners of the texel
						// The FMath::Sqrt(.5f) is to normalize (Vertex.TriangleTangentX + Vertex.TriangleTangentY), which are orthogonal unit vectors.
						const FVector4f CornerOffset = FMath::Sqrt(.5f) * (Vertex.TriangleTangentX + Vertex.TriangleTangentY) * SampleRadius * SceneConstants.VisibilityTangentOffsetSampleRadiusScale;
						const FLightRay TexelRay(
							TexelCenterOffset + CornerOffset,
							TexelCenterOffset - CornerOffset,
							NULL,
							NULL
							);

file
namespace    Lightmass
function     FVector2f FStaticLightingSystem::CalculatePointAreaShadowing

				//@todo - the rays cross over on the way to the light and mess up penumbra shapes.  
				//@todo - need to use more than texel size, otherwise BSP generates lots of texels that become half shadowed at corners
				SampleOffset = Vertex.WorldTangentX * LightPositionSamples(RayIndex).DiskPosition.X * SampleRadius * SceneConstants.VisibilityTangentOffsetSampleRadiusScale
					+ Vertex.WorldTangentY * LightPositionSamples(RayIndex).DiskPosition.Y * SampleRadius * SceneConstants.VisibilityTangentOffsetSampleRadiusScale;
					*/
			}

			float DistSqr = LightVector.SizeSquared3() + KINDA_SMALL_NUMBER;
			float SamplePDF = CurrentSample.PDF * -Dot3( CurrentSample.Normal, LightVector ) / ( DistSqr * FMath::Sqrt( DistSqr ) );
			if( SamplePDF <= 0.0f )
			{
				continue;
			}

			FVector4f NormalForOffset = Vertex.WorldTangentZ;

file
namespace    Lightmass
function     void FStaticLightingSystem::TraceToTexelCorner

	// Vector from the center to one of the corners of the texel
	// The FMath::Sqrt(.5f) is to normalize (Vertex.TriangleTangentX + Vertex.TriangleTangentY), which are orthogonal unit vectors.
	const FVector4f CornerOffset = FMath::Sqrt(.5f) * (CornerSigns.X * FullVertex.TriangleTangentX + CornerSigns.Y * FullVertex.TriangleTangentY) * TexelRadius * SceneConstants.VisibilityTangentOffsetSampleRadiusScale;
	const FLightRay TexelRay(
		TexelCenterOffset,
		TexelCenterOffset + CornerOffset,
		NULL,
		NULL
		);

file
namespace    Lightmass
class        class FStaticLightingSceneConstants

	 * This is only used when bAccountForTexelSize is true.
	 */
	float VisibilityTangentOffsetSampleRadiusScale;

	/** 
	 * Smallest texel radius allowed, useful for clamping edge cases where some texels have a radius of 0. 
	 * This should be smaller than the smallest valid texel radius in the scene.
	 */
	float SmallestTexelRadius;