UE4根据物体设定摄像机位置

.h

// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "CameraPointActor.generated.h"

UCLASS()
class A418_API ACameraPointActor : public AActor
{
	GENERATED_BODY()
	
public:	
	// Sets default values for this actor's properties
	ACameraPointActor();

protected:
	// Called when the game starts or when spawned
	virtual void BeginPlay() override;

public:	
	// Called every frame
	virtual void Tick(float DeltaTime) override;
	
	float GetMinProjection(FVector Normal, const TArray &Points, const TArray &Sizes);
	UFUNCTION(BlueprintCallable, Category = "AA")
	FVector CalcCameraLocationByTargetPoints(const TArray &Points, const TArray &Sizes,
		const FRotator CameraRotation, const float FovXDegrees, const float AspectRatio, const float FovLeftMargin, 
		const float FovRightMargin, const float FovBottomMargin, const float FovTopMargin);
};

.cpp

// Fill out your copyright notice in the Description page of Project Settings.

#include "CameraPointActor.h"
#include "UnrealMathUtility.h"


// Sets default values
ACameraPointActor::ACameraPointActor()
{
 	// Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
	PrimaryActorTick.bCanEverTick = true;

}

// Called when the game starts or when spawned
void ACameraPointActor::BeginPlay()
{
	Super::BeginPlay();
	
}

// Called every frame
void ACameraPointActor::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);

}

// 通过将Points给出的坐标组投影到Normal轴上获得最小的一个结果（考虑到它，我们也将偏移大小）。
float ACameraPointActor::GetMinProjection(FVector Normal, const TArray &Points, const TArray &Sizes)
{
	float Retval = MAX_FLT;

	for (int i = 0; i < Points.Num(); ++i)
	{
		Retval = FMath::Min(Retval, FVector::DotProduct(Points[i], Normal) - Sizes[i]);
	}

	return Retval;
}

// 根据目标位置/大小和摄像机方向确定最佳摄像机位置
FVector ACameraPointActor::CalcCameraLocationByTargetPoints(const TArray &Points, const TArray &Sizes, const FRotator CameraRotation, const float FovXDegrees, const float AspectRatio, const float FovLeftMargin, const float FovRightMargin, const float FovBottomMargin, const float FovTopMargin)
{
	const float HalfFov_X = FMath::DegreesToRadians(FovXDegrees*0.5f);

	const float HalfTanX = FMath::Tan(HalfFov_X);
	const float HalfTanY = HalfTanX / AspectRatio;

	//支持不对称的安全框架
	//获取上/下/左/右安全框的视角
	const float HalfFovLeft = FMath::Atan(HalfTanX * (1.0f - FovLeftMargin * 2.0f));
	const float HalfFovRight = FMath::Atan(HalfTanX * (1.0f - FovRightMargin * 2.0f));
	const float HalfFovBottom = FMath::Atan(HalfTanY * (1.0f - FovBottomMargin * 2.0f));
	const float HalfFovTop = FMath::Atan(HalfTanY * (1.0f - FovTopMargin * 2.0f));

	const float HalfFovLeftDeg = FMath::RadiansToDegrees(HalfFovLeft);
	const float HalfFovRightDeg = FMath::RadiansToDegrees(HalfFovRight);
	const float HalfFovBottomDeg = FMath::RadiansToDegrees(HalfFovBottom);
	const float HalfFovTopDeg = FMath::RadiansToDegrees(HalfFovTop);

	//通过使坐标轴平行于摄像机的坐标轴来简化计算。
	//原样调整原点，仅旋转
	//请注意，相机的坐标不是原点。
	TArray PointsCS;
	PointsCS.SetNum(Points.Num());

	for (int i = 0; i < Points.Num(); ++i)
	{
		PointsCS[i] = CameraRotation.UnrotateVector(Points[i]);
	}

	// 在此处存储计算结果
	FVector CameraLocationCS;


	// 左右面的约束
	float XbyLR;
	float Dydx;
	{
		// 在与摄像机平行的坐标系中，可以在XY平面上计算
		const FVector LeftBoundNormalCS = FVector::RightVector.RotateAngleAxis(-HalfFovLeftDeg, FVector::UpVector);
		const float LeftBoundPosCS = GetMinProjection(LeftBoundNormalCS, PointsCS, Sizes);

		const FVector RightBoundNormalCS = -FVector::RightVector.RotateAngleAxis(HalfFovRightDeg, FVector::UpVector);
		const float RightBoundPosCS = GetMinProjection(RightBoundNormalCS, PointsCS, Sizes);

		//求解联立方程。
		// Q是投影在XY平面上的左右面的交点
		// dot(Q, LeftBoundNormalCS) = LeftBoundPosCS
		// dot(Q, RightBoundNormalCS) = RightBoundPosCS
		// 
		// 组织并​​获得以下公式
		const float QX = (RightBoundNormalCS.Y*LeftBoundPosCS - LeftBoundNormalCS.Y*RightBoundPosCS) / (LeftBoundNormalCS.X*RightBoundNormalCS.Y - LeftBoundNormalCS.Y*RightBoundNormalCS.X);
		const float QY = (LeftBoundPosCS - QX * LeftBoundNormalCS.X) / LeftBoundNormalCS.Y;

		//我们会暂时存储解决方案。
		// X是临时值，有必要将其与从上下两个条件获得的值进行比较。
		// Y由此决定。
		//Z在检查上下表面的状况之前不理解。
		XbyLR = QX;
		CameraLocationCS.Y = QY;

		// 保存Y相对于X的变化量（处理安全帧不对称）
		Dydx = HalfTanX * (FovLeftMargin - FovRightMargin);
	}

	// 上下面的约束
	float XbyTB;
	float Dzdx;
	{
		// 在XZ平面上计算
		const FVector BottomBoundNormalCS = FVector::UpVector.RotateAngleAxis(-HalfFovBottomDeg, -FVector::RightVector);
		const float BottomBoundPosCS = GetMinProjection(BottomBoundNormalCS, PointsCS, Sizes);

		const FVector TopBoundNormalCS = -FVector::UpVector.RotateAngleAxis(HalfFovTopDeg, -FVector::RightVector);
		const float TopBoundPosCS = GetMinProjection(TopBoundNormalCS, PointsCS, Sizes);

		// 与左/右侧相同。
		const float QX = (TopBoundNormalCS.Z*BottomBoundPosCS - BottomBoundNormalCS.Z*TopBoundPosCS) / (BottomBoundNormalCS.X*TopBoundNormalCS.Z - BottomBoundNormalCS.Z*TopBoundNormalCS.X);
		const float QZ = (BottomBoundPosCS - QX * BottomBoundNormalCS.X) / BottomBoundNormalCS.Z;

		// 从左/右，上/下条件（向后拉）获得的X中较小的X是获得的值。
		XbyTB = QX;
		CameraLocationCS.Z = QZ;

		// 保存Z相对于X的变化量（处理安全帧不对称）
		Dzdx = HalfTanY * (FovBottomMargin - FovTopMargin);
	}

	CameraLocationCS.X = FMath::Min(XbyLR, XbyTB);
	CameraLocationCS.Y += (Dydx * (CameraLocationCS.X - XbyLR));
	CameraLocationCS.Z += (Dzdx * (CameraLocationCS.X - XbyTB));

	// 恢复到世界坐标并返回
	return CameraRotation.RotateVector(CameraLocationCS);
}