file
function     void FLightmassExporter::WriteSceneSettings

		VERIFYLIGHTMASSINI(GConfig->GetBool(TEXT("DevOptions.PhotonMapping"), TEXT("bUsePhotonDirectLightingInFinalGather"), bConfigBool, GLightmassIni));
		Scene.PhotonMappingSettings.bUsePhotonDirectLightingInFinalGather = bConfigBool;
		VERIFYLIGHTMASSINI(GConfig->GetBool(TEXT("DevOptions.PhotonMapping"), TEXT("bVisualizeCachedApproximateDirectLighting"), bConfigBool, GLightmassIni));
		Scene.PhotonMappingSettings.bVisualizeCachedApproximateDirectLighting = bConfigBool;
		VERIFYLIGHTMASSINI(GConfig->GetBool(TEXT("DevOptions.PhotonMapping"), TEXT("bUseIrradiancePhotons"), bConfigBool, GLightmassIni));
		Scene.PhotonMappingSettings.bUseIrradiancePhotons = bConfigBool;
		VERIFYLIGHTMASSINI(GConfig->GetBool(TEXT("DevOptions.PhotonMapping"), TEXT("bCacheIrradiancePhotonsOnSurfaces"), bConfigBool, GLightmassIni));
		Scene.PhotonMappingSettings.bCacheIrradiancePhotonsOnSurfaces = bConfigBool;
		VERIFYLIGHTMASSINI(GConfig->GetBool(TEXT("DevOptions.PhotonMapping"), TEXT("bVisualizePhotonPaths"), bConfigBool, GLightmassIni));
		Scene.PhotonMappingSettings.bVisualizePhotonPaths = bConfigBool;

file
namespace    Lightmass
function     void FStaticLightingSystem::InitializePhotonSettings

	Stats.NumFirstPassPhotonsRequested = 0;
	// Only emit direct photons if they will be used for lighting
	if (GeneralSettings.NumIndirectLightingBounces > 0 || PhotonMappingSettings.bVisualizeCachedApproximateDirectLighting)
	{
		for (int32 LightIndex = 0; LightIndex < Lights.Num(); LightIndex++)
		{
			Stats.NumFirstPassPhotonsRequested += Lights[LightIndex]->GetNumDirectPhotons(PhotonMappingSettings.DirectPhotonDensity);
		}

file
namespace    Lightmass
function     void FStaticLightingSystem::EmitDirectPhotons

	{
		if (GeneralSettings.ViewSingleBounceNumber < 0
			|| PhotonMappingSettings.bVisualizeCachedApproximateDirectLighting && GeneralSettings.ViewSingleBounceNumber == 0 
			|| PhotonMappingSettings.bUseFinalGathering && GeneralSettings.ViewSingleBounceNumber == 1)
		{
			if (PhotonMappingSettings.bUseIrradiancePhotons)
			{
				int32 NumDirectIrradiancePhotons = 0;
				for (int32 ArrayIndex = 0; ArrayIndex < IrradiancePhotons.Num(); ArrayIndex++)

file
namespace    Lightmass
function     void FStaticLightingSystem::MarkIrradiancePhotonsWorkRange

		if ((PhotonMappingSettings.bUseFinalGathering && GeneralSettings.NumIndirectLightingBounces > 0)
			// Or if photon mapping is being used for direct lighting.
			|| PhotonMappingSettings.bVisualizeCachedApproximateDirectLighting)
		{
			// Find a nearby direct photon
			const bool bHasDirectContribution = FindAnyNearbyPhoton(DirectPhotonMap, CurrentIrradiancePhoton.GetPosition(), PhotonMappingSettings.DirectPhotonSearchDistance, false);
			if (bHasDirectContribution)
			{
				// Mark the irradiance photon has having direct contribution, which will be used to reduce the search radius for this irradiance photon,

file
namespace    Lightmass
function     void FStaticLightingSystem::CalculateIrradiancePhotonsWorkRange

		if (((PhotonMappingSettings.bUseFinalGathering && GeneralSettings.NumIndirectLightingBounces > 0)
			// Or if photon mapping is being used for direct lighting.
			|| PhotonMappingSettings.bVisualizeCachedApproximateDirectLighting)
			&& PhotonMappingSettings.bUsePhotonDirectLightingInFinalGather)
		{
			const FLinearColor DirectPhotonIrradiance = CalculatePhotonIrradiance(
				DirectPhotonMap, 
				NumPhotonsEmittedDirect, 
				PhotonMappingSettings.NumIrradianceCalculationPhotons, 

file
namespace    Lightmass
function     void FStaticLightingSystem::CalculateIrradiancePhotonsWorkRange

				|| (PhotonMappingSettings.bUseFinalGathering && GeneralSettings.ViewSingleBounceNumber == 1)
				|| (!PhotonMappingSettings.bUseFinalGathering && GeneralSettings.ViewSingleBounceNumber == 0)
				|| (PhotonMappingSettings.bVisualizeCachedApproximateDirectLighting && GeneralSettings.ViewSingleBounceNumber == 0))
			{
				AccumulatedIrradiance = DirectPhotonIrradiance;
			}
		}

		// If we are final gathering, first bounce photons are actually the second lighting bounce since the final gather is the first bounce

file
namespace    Lightmass
function     void FStaticLightingSystem::FinalizeSurfaceCacheTextureMapping

					VertexOffsets.Add(FVector3f(0, 0, 0));

					CalculateApproximateDirectLighting(CurrentVertex, TexelToVertex.TexelRadius, VertexOffsets, .1f, true, true, bDebugThisTexel && PhotonMappingSettings.bVisualizeCachedApproximateDirectLighting, MappingContext, DirectLighting, Unused2);
					FinalIncidentLighting += DirectLighting.IncidentLighting;
				}

				const bool bTranslucent = TextureMapping->Mesh->IsTranslucent(TexelToVertex.ElementIndex);
				const FLinearColor Reflectance = (bTranslucent ? FLinearColor::Black : TextureMapping->Mesh->EvaluateTotalReflectance(CurrentVertex, TexelToVertex.ElementIndex)) * (float)INV_PI;
				// Combine all the lighting and surface reflectance so the final gather ray only needs one memory fetch

file
namespace    Lightmass
function     void FStaticLightingSystem::ProcessTextureMapping

	{
		const double DirectLightingStartTime = FPlatformTime::Seconds();
		const bool bCalculateDirectLightingFromPhotons = PhotonMappingSettings.bUsePhotonMapping && PhotonMappingSettings.bVisualizeCachedApproximateDirectLighting;
		// Only continue if photon mapping will not be used for direct lighting
		if (!bCalculateDirectLightingFromPhotons)
		{
			// Iterate over each light that is relevant to the direct lighting of the mesh
			for (int32 LightIndex = 0; LightIndex < TextureMapping->Mesh->RelevantLights.Num(); LightIndex++)
			{

file
namespace    Lightmass
function     void FStaticLightingSystem::CalculateDirectLightingTextureMappingPhotonMap

					{
						// Trace a ray into the current texel to get a good representation of what the final gather will see.
						// Speed does not matter here since bVisualizeCachedApproximateDirectLighting is only used for debugging.
						const FLightRay TexelRay(
							CurrentVertex.WorldPosition + CurrentVertex.WorldTangentZ * TexelToVertex.TexelRadius,
							CurrentVertex.WorldPosition - CurrentVertex.WorldTangentZ * TexelToVertex.TexelRadius,
							TextureMapping,
							NULL
							);

file
namespace    Lightmass
class        class FPhotonMappingSettings

	* This is mainly useful for debugging what the final gather rays see.
	*/
	bool bVisualizeCachedApproximateDirectLighting;

	/** Debugging - whether to use the optimization of caching irradiance calculations in deposited photons (called Irradiance photons). */
	bool bUseIrradiancePhotons;

	/** 
	* Debugging - whether to cache the result of the search for the nearest irradiance photon on surfaces.