（Unreal Engine）场景捕捉组件2D坐标与世界坐标的相互转换

ProjectSceneCapture2DToWorld.cpp

#include "Components/SceneCaptureComponent2D.h"
#include "Engine/TextureRenderTarget2D.h"

void ProjectSceneCaptureToWorld(const class USceneCaptureComponent2D* sceneCaptureCompone2D, const FVector2D& sceneCapturePosition, FVector& worldPosition, FVector& worldDirection)
{
	// 计算视口矩阵
	const FTransform& transform = sceneCaptureCompone2D->GetComponentToWorld();
	FMatrix viewMatrix = transform.ToInverseMatrixWithScale();
	viewMatrix = viewMatrix * FMatrix(FPlane(0, 0, 1, 0), FPlane(1, 0, 0, 0), FPlane(0, 1, 0, 0), FPlane(0, 0, 0, 1));

	// 计算投影矩阵
	const float FOV = sceneCaptureCompone2D->FOVAngle * (float)PI / 360.0f;
	FIntPoint captureSize(sceneCaptureCompone2D->TextureTarget->GetSurfaceWidth(), sceneCaptureCompone2D->TextureTarget->GetSurfaceHeight());
	float XAxisMultiplier;
	float YAxisMultiplier;
	if (captureSize.X > captureSize.Y)
	{
		XAxisMultiplier = 1.0f;
		YAxisMultiplier = captureSize.X / (float)captureSize.Y;
	}
	else
	{
		XAxisMultiplier = captureSize.Y / (float)captureSize.X;
		YAxisMultiplier = 1.0f;
	}
	FMatrix projectionMatrix = FReversedZPerspectiveMatrix(FOV, FOV, XAxisMultiplier, YAxisMultiplier, GNearClippingPlane, GNearClippingPlane);

	const FMatrix inverseViewMatrix = viewMatrix.InverseFast();
	const FMatrix invProjectionMatrix = projectionMatrix.Inverse();
	const FIntRect viewRect = FIntRect(0, 0, captureSize.X, captureSize.Y);
	FSceneView::DeprojectScreenToWorld(sceneCapturePosition, viewRect, inverseViewMatrix, invProjectionMatrix, worldPosition, worldDirection);
}

bool ProjectWorldToSceneCapture(const FVector& worldPosition, const class USceneCaptureComponent2D* sceneCaptureCompone2D, FVector2D& sceneCapturePosition)
{
	// 计算视口矩阵
	const FTransform& transform = sceneCaptureCompone2D->GetComponentToWorld();
	FMatrix viewMatrix = transform.ToInverseMatrixWithScale();
	viewMatrix = viewMatrix * FMatrix(FPlane(0, 0, 1, 0), FPlane(1, 0, 0, 0), FPlane(0, 1, 0, 0), FPlane(0, 0, 0, 1));

	// 计算投影矩阵
	const float FOV = sceneCaptureCompone2D->FOVAngle * (float)PI / 360.0f;
	FIntPoint captureSize(sceneCaptureCompone2D->TextureTarget->GetSurfaceWidth(), sceneCaptureCompone2D->TextureTarget->GetSurfaceHeight());
	float XAxisMultiplier;
	float YAxisMultiplier;
	if (captureSize.X > captureSize.Y)
	{
		XAxisMultiplier = 1.0f;
		YAxisMultiplier = captureSize.X / (float)captureSize.Y;
	}
	else
	{
		XAxisMultiplier = captureSize.Y / (float)captureSize.X;
		YAxisMultiplier = 1.0f;
	}
	FMatrix projectionMatrix = FReversedZPerspectiveMatrix(FOV, FOV, XAxisMultiplier, YAxisMultiplier, GNearClippingPlane, GNearClippingPlane);

	FMatrix viewProjectionMatrix = viewMatrix * projectionMatrix;
	FPlane result = viewProjectionMatrix.TransformFVector4(FVector4(worldPosition, 1.f));
	const FIntRect viewRect = FIntRect(0, 0, captureSize.X, captureSize.Y);
	if (result.W > 0.0f)
	{
		// the result of this will be x and y coords in -1..1 projection space
		const float RHW = 1.0f / result.W;
		FPlane posInScreenSpace = FPlane(result.X * RHW, result.Y * RHW, result.Z * RHW, result.W);

		// Move from projection space to normalized 0..1 UI space
		const float normalizedX = (posInScreenSpace.X / 2.f) + 0.5f;
		const float normalizedY = 1.f - (posInScreenSpace.Y / 2.f) - 0.5f;

		FVector2D rayStartViewRectSpace(
			(normalizedX * (float)viewRect.Width()),
			(normalizedY * (float)viewRect.Height())
		);

		sceneCapturePosition = rayStartViewRectSpace + FVector2D(static_cast<float>(viewRect.Min.X), static_cast<float>(viewRect.Min.Y));

		return true;
	}

	return false;
}