C++ FViewInfo::IsPerspectiveProjection方法代码示例

void FDecalRendering::BuildVisibleDecalList(const FScene& Scene, const FViewInfo& View, EDecalRenderStage DecalRenderStage, FTransientDecalRenderDataList& OutVisibleDecals)
{
	QUICK_SCOPE_CYCLE_COUNTER(BuildVisibleDecalList);

	OutVisibleDecals.Empty(Scene.Decals.Num());

	const float FadeMultiplier = CVarDecalFadeScreenSizeMultiplier.GetValueOnRenderThread();
	const EShaderPlatform ShaderPlatform = View.GetShaderPlatform();

	const bool bIsPerspectiveProjection = View.IsPerspectiveProjection();

	// Build a list of decals that need to be rendered for this view in SortedDecals
	for (const FDeferredDecalProxy* DecalProxy : Scene.Decals)
	{
		bool bIsShown = true;

		if (!DecalProxy->IsShown(&View))
		{
			bIsShown = false;
		}

		const FMatrix ComponentToWorldMatrix = DecalProxy->ComponentTrans.ToMatrixWithScale();

		// can be optimized as we test against a sphere around the box instead of the box itself
		const float ConservativeRadius = FMath::Sqrt(
				ComponentToWorldMatrix.GetScaledAxis(EAxis::X).SizeSquared() +
				ComponentToWorldMatrix.GetScaledAxis(EAxis::Y).SizeSquared() +
				ComponentToWorldMatrix.GetScaledAxis(EAxis::Z).SizeSquared());

		// can be optimized as the test is too conservative (sphere instead of OBB)
		if(ConservativeRadius < SMALL_NUMBER || !View.ViewFrustum.IntersectSphere(ComponentToWorldMatrix.GetOrigin(), ConservativeRadius))
		{
			bIsShown = false;
		}

		if (bIsShown)
		{
			FTransientDecalRenderData Data(Scene, DecalProxy, ConservativeRadius);
			
			// filter out decals with blend modes that are not supported on current platform
			if (IsBlendModeSupported(ShaderPlatform, Data.DecalBlendMode))
			{
				if (bIsPerspectiveProjection && Data.DecalProxy->Component->FadeScreenSize != 0.0f)
				{
					float Distance = (View.ViewMatrices.ViewOrigin - ComponentToWorldMatrix.GetOrigin()).Size();
					float Radius = ComponentToWorldMatrix.GetMaximumAxisScale();
					float CurrentScreenSize = ((Radius / Distance) * FadeMultiplier);

					// fading coefficient needs to increase with increasing field of view and decrease with increasing resolution
					// FadeCoeffScale is an empirically determined constant to bring us back roughly to fraction of screen size for FadeScreenSize
					const float FadeCoeffScale = 600.0f;
					float FOVFactor = ((2.0f/View.ViewMatrices.ProjMatrix.M[0][0]) / View.ViewRect.Width()) * FadeCoeffScale;
					float FadeCoeff = Data.DecalProxy->Component->FadeScreenSize * FOVFactor;
					float FadeRange = FadeCoeff * 0.5f;

					float Alpha = (CurrentScreenSize - FadeCoeff) / FadeRange;
					Data.FadeAlpha = FMath::Min(Alpha, 1.0f);
				}

				EDecalRenderStage LocalDecalRenderStage = FDecalRenderingCommon::ComputeRenderStage(ShaderPlatform, Data.DecalBlendMode);

				// we could do this test earlier to avoid the decal intersection but getting DecalBlendMode also costs
				if (View.Family->EngineShowFlags.ShaderComplexity || (DecalRenderStage == LocalDecalRenderStage && Data.FadeAlpha>0.0f) )
				{
					OutVisibleDecals.Add(Data);
				}
			}
		}
	}

	if (OutVisibleDecals.Num() > 0)
	{
		// Sort by sort order to allow control over composited result
		// Then sort decals by state to reduce render target switches
		// Also sort by component since Sort() is not stable
		struct FCompareFTransientDecalRenderData
		{
			FORCEINLINE bool operator()(const FTransientDecalRenderData& A, const FTransientDecalRenderData& B) const
			{
				if (B.DecalProxy->SortOrder != A.DecalProxy->SortOrder)
				{ 
					return A.DecalProxy->SortOrder < B.DecalProxy->SortOrder;
				}
				// bHasNormal here is more important then blend mode because we want to render every decals that output normals before those that read normal.
				if (B.bHasNormal != A.bHasNormal)
				{
					return B.bHasNormal < A.bHasNormal; // < so that those outputting normal are first.
				}
				if (B.DecalBlendMode != A.DecalBlendMode)
				{
					return (int32)B.DecalBlendMode < (int32)A.DecalBlendMode;
				}
				// Batch decals with the same material together
				if (B.MaterialProxy != A.MaterialProxy)
				{
					return B.MaterialProxy < A.MaterialProxy;
				}
				return (PTRINT)B.DecalProxy->Component < (PTRINT)A.DecalProxy->Component;
			}
		};
//.........这里部分代码省略.........