UE4获取空间坐标点对应颜色值

原理：

把360方向均分成4分，分别用四个90°的2DCapture渲染到renderTarget2D上，然后通过3D到2D renderTarget2D的映射关系，读取RenderTarget2D的颜色值

应用：点云数据，颜色采集

 

得到3D到2DRenderTarget2D的映射关系：

代码来源：github ：

VictoryBPFunctionLibrary.h

https://github.com/UngureanuAdrian/RPGQuantumGate/blob/f1af44ab32cdbde8a90cf7bad170995693898be3/Plugins/VictoryPlugin25/Source/VictoryBPLibrary/Public/VictoryBPFunctionLibrary.h

// Fill out your copyright notice in the Description page of Project Settings.
#include "UtilLibrary.h"
#include "Engine/TextureRenderTarget2D.h"
#include "Engine/SceneCapture2D.h"
#include "Components/SceneCaptureComponent2D.h"
#include "Engine.h"
#include "Engine/World.h"
#include "Kismet/KismetSystemLibrary.h"
#include "MyProject.h"
#include "RHI.h"
bool UUtilLibrary::CaptureComponent2D_Project(class USceneCaptureComponent2D* Target,  FVector Location, FVector2D& OutPixelLocation)
{
        if ((Target == nullptr) || (Target->TextureTarget == nullptr))
        {
               return false;
        }
        const FTransform& Transform = Target->GetComponentToWorld();
        FMatrix ViewMatrix = Transform.ToInverseMatrixWithScale();
        FVector ViewLocation = Transform.GetTranslation();
        // swap axis st. x=z,y=x,z=y (unreal coord space) so that z is up
        ViewMatrix = ViewMatrix * FMatrix(
               FPlane(0, 0, 1, 0),
               FPlane(1, 0, 0, 0),
               FPlane(0, 1, 0, 0),
               FPlane(0, 0, 0, 1));
        const float FOV = Target->FOVAngle * (float)PI / 360.0f;
        FIntPoint CaptureSize(Target->TextureTarget->GetSurfaceWidth(),  Target->TextureTarget->GetSurfaceHeight());
        float XAxisMultiplier;
        float YAxisMultiplier;
        if (CaptureSize.X > CaptureSize.Y)
        {
               // if the viewport is wider than it is tall
               XAxisMultiplier = 1.0f;
               YAxisMultiplier = CaptureSize.X / (float)CaptureSize.Y;
        }
        else
        {
               // if the viewport is taller than it is wide
               XAxisMultiplier = CaptureSize.Y / (float)CaptureSize.X;
               YAxisMultiplier = 1.0f;
        }
        FMatrix    ProjectionMatrix = FReversedZPerspectiveMatrix(
               FOV,
               FOV,
               XAxisMultiplier,
               YAxisMultiplier,
               GNearClippingPlane,
               GNearClippingPlane
        );
        FMatrix ViewProjectionMatrix = ViewMatrix * ProjectionMatrix;
        FVector4 ScreenPoint = ViewProjectionMatrix.TransformFVector4(FVector4(Location,  1));
        if (ScreenPoint.W > 0.0f)
        {
               float InvW = 1.0f / ScreenPoint.W;
               float Y = (GProjectionSignY > 0.0f) ? ScreenPoint.Y : 1.0f - ScreenPoint.Y;    //GProjectionSignY此变量需要引入RHI库
               FIntRect ViewRect = FIntRect(0, 0, CaptureSize.X, CaptureSize.Y);
               OutPixelLocation = FVector2D(
                       ViewRect.Min.X + (0.5f + ScreenPoint.X * 0.5f * InvW) *  ViewRect.Width(),
                       ViewRect.Min.Y + (0.5f - Y * 0.5f * InvW) * ViewRect.Height()
               );
               return true;
        }
        return false;
}

实现：

创建四个完全一致的RenderTarget2D

实例化四个2DCapture，并把四个renderterget2D传进去：

bool  ULidarBase::InitLidarComponent_YH(int32 LidarLineNum, USceneComponent* Parent,  TArray  RenderTargets)
{
        if (LidarLineNum<=0||Parent == nullptr|| RenderTargets.Num()<4)
        {
               return false;
        }
        USceneComponent* LidarRoot = NewObject(GetOwner());
        LidarRoot->AttachToComponent(Parent,  FAttachmentTransformRules::KeepRelativeTransform);
        LidarRoot->RegisterComponent();
        ThisLidarRoot = LidarRoot;
        for (int32 j = 0; j < 4; j++)
        {
               USceneCaptureComponent2D* lidarCamera =  NewObject(GetOwner());
               lidarCamera->AttachToComponent(Parent,  FAttachmentTransformRules::KeepRelativeTransform);
               lidarCamera->RegisterComponent();
               lidarCamera->TextureTarget = RenderTargets[j];
               lidarCamera->CaptureSource = ESceneCaptureSource::SCS_FinalColorLDR;
               lidarCamera->PrimitiveRenderMode =  ESceneCapturePrimitiveRenderMode::PRM_RenderScenePrimitives;
               lidarCamera->ProjectionType = ECameraProjectionMode::Perspective;
               lidarCamera->FOVAngle = 90.0;
               lidarCamera->SetRelativeRotation(FRotator(0.0, 90.0*j, 0.0));
               MainCamera2Ds.Add(lidarCamera);
        }
        float DirRotaNum = 360.0 / LidarLineNum;
        for (int32 i = 0; i < LidarLineNum; i++)
        {
               USceneComponent* LidarParent = NewObject(GetOwner());
               LidarParent->AttachToComponent(LidarRoot,  FAttachmentTransformRules::KeepRelativeTransform);
               LidarParent->RegisterComponent();
               LidarParent->SetRelativeRotation(FRotator(0.0, DirRotaNum*i, 0.0));
               LidarTmap.Add(i, LidarParent);
        }
        return LidarRoot->IsRegistered();
}

蓝图中调用：

运行：

结果：点坐标通过射线检测得到