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目录
原理
效果
步骤
源码
原理
先设置绘制线段的起点和终点，然后我们将起点和终点的高度升高，然后通过插值，在起点和终点之间添加多个点，再由这些点向地心发出射线，这样我们就可以获取到这些点在地表的投影点，最后将投影点连起来就是地表贴合线。
注意：使用该方法时，需要保证地形加载完毕，因为只要地形加载后地表才会有碰撞信息，才能被射线检测到
效果
步骤
1. 在“xxx.Build.cs”中引入“CesiumRuntime”模块
2. 新建一个Actor类，这里命名为“SurfaceLineActor”
在“SurfaceLineActor.h”中添加所需头文件
定义一个函数“CalculatePointsOnSurface”用于计算地表点，该函数需要传入起点终点的经纬度、细分点数、起终点向上偏移的距离
再定义一个函数用于绘制地表贴合线，该函数需要传入地表点数组、线的颜色、线的粗细共3个参数。
定义地心坐标、添加一个LineBatchComponent组件用于高效绘制线条、定义一个数组“Points”用于储存起终点之间的点
实现函数“CalculatePointsOnSurface”如下
TArray<FVector> ASurfaceLineActor::CalculatePointsOnSurface(FVector StartPointLLA, FVector EndPointLLA, int32 NumberOfSegments, double TraceUpOffset)
{//将起点和终点拔高一段距离以方便往地心打射线StartPointLLA = StartPointLLA + FVector(0, 0, TraceUpOffset);EndPointLLA = EndPointLLA + FVector(0, 0, TraceUpOffset);//获取GeoreferenceACesiumGeoreference* Georeference = ACesiumGeoreference::GetDefaultGeoreference(GetWorld());if (!Georeference){UE_LOG(LogTemp, Warning, TEXT("SurfaceLineActor: CesiumGeoreference not found. Cannot calculate surface points."));}//将起终点（经纬高）转换为起终点（UE世界坐标）FVector StartPoint = Georeference->TransformLongitudeLatitudeHeightPositionToUnreal(StartPointLLA);FVector EndPoint = Georeference->TransformLongitudeLatitudeHeightPositionToUnreal(EndPointLLA);Points.Empty();if (NumberOfSegments <= 0) // 分段数不满足要求，返回起点和终点{// 如果段数无效，至少包含起点和终点Points.Add(StartPoint);if (StartPoint != EndPoint) // 避免重复添加同一点{Points.Add(EndPoint);}}else{//Points.Reserve(NumberOfSegments + 1); // 预分配空间提高效率for (int32 i = 0; i < NumberOfSegments; ++i){float T = static_cast<float>(i) / static_cast<float>(NumberOfSegments);FVector CurrentPoint = FMath::Lerp(StartPoint, EndPoint, T); // 使用 FMath::Lerp 进行线性插值计算点的坐标Points.Add(CurrentPoint);}}// 用于存储射线检测到的地表点TArray<FVector> CalculatedSurfacePoints;//起点和终点构成的连线中每个点都朝地心发出射线for (int32 i = 0; i < Points.Num(); ++i){FHitResult HitResult;FCollisionQueryParams QueryParams;QueryParams.AddIgnoredActor(this); // 射线检测忽视自身//QueryParams.AddIgnoredActors(ActorsToIgnore); // 忽视射线检测的ActorQueryParams.bTraceComplex = true; // 使用复杂碰撞QueryParams.bReturnPhysicalMaterial = false; // 是否检测物理材料ECollisionChannel TraceChannel = ECC_Visibility;UWorld* World = GetWorld();bool bHit = World->LineTraceSingleByChannel(HitResult, // 射线检测结果Points[i], // 射线起点EarthOrigin, // 射线终点（地心）TraceChannel, // 射线碰撞通道QueryParams // 射线碰撞其他参数);画射线检测（非必需）//DrawDebugLine(// GetWorld(),// Points[i], //起点// EarthOrigin, //终点（地心）// bHit ? FColor::Green : FColor::Red, //颜色// false, // false表示它持续“LifeTime”，如果LifeTime为0，则持续一帧// 0.0, // DebugLine生命周期时长// 0, // DepthPriority (0 for SDPG_World)// 2.0f//);if (bHit){画射线碰撞点（非必需）//DrawDebugSphere(// GetWorld(),// HitResult.Location,// 30.0f, // Radius// 12, // Segments// FColor::Cyan,// false, // Persistent lines// 0.0f // Lifetime//);FVector OutHitLocation = HitResult.ImpactPoint;CalculatedSurfacePoints.Add(OutHitLocation);}}return CalculatedSurfacePoints;
}3. 测试一下“CalculatePointsOnSurface”函数是否生效，这里设置起点为成都市市中心终点为都江堰
运行后可以看到地表点位置基本准确
4. 接下来只需要通过LineBatchComponent组件将地表点连线即可
函数“DrawSurfaceLine”实现如下
void ASurfaceLineActor::DrawSurfaceLine(TArray<FVector> SurfacePoints, FLinearColor LineColor, float LineThickness)
{if (!LineBatchComponent){UE_LOG(LogTemp, Warning, TEXT("SurfaceLineActor: LineBatchComponent is null."));return;}LineBatchComponent->Flush(); // 清除之前的线if (SurfacePoints.Num() >= 2){for (int32 i = 0; i < SurfacePoints.Num() - 1; ++i){if (SurfacePoints[i].ContainsNaN() || SurfacePoints[i + 1].ContainsNaN()){UE_LOG(LogTemp, Warning, TEXT("SurfaceLineActor: Encountered NaN point at segment %d, skipping draw."), i);continue;}LineBatchComponent->DrawLine(SurfacePoints[i],SurfacePoints[i + 1],LineColor,SDPG_World, // 场景深度优先级组-根据渲染顺序需要进行调整LineThickness,0.0f // 线的生命周期时长：0表示无限生命);}}
}再通过蓝图在获取地表点数组后传入函数 “DrawSurfaceLine”
此时效果如下：
5. 选取山地进行测试，插值数量设置为200，此时运行效果如下
源码
“SurfaceLineActor.h”
// Fill out your copyright notice in the Description page of Project Settings.#pragma once#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "Components/LineBatchComponent.h"
#include "CesiumGeoreference.h"
#include "SurfaceLineActor.generated.h"UCLASS()
class GLOBEPAWNTEST_API ASurfaceLineActor : public AActor
{GENERATED_BODY()public: // Sets default values for this actor's propertiesASurfaceLineActor();// 计算地表点UFUNCTION(BlueprintCallable, Category = "Line Properties")TArray<FVector> CalculatePointsOnSurface(FVector StartPointLLA = FVector(0, 0, 0),FVector EndPointLLA = FVector(0, 0, 0),int32 NumberOfSegments = 50, // 线段细分数 (越高质量越好，但性能开销越大)double TraceUpOffset = 100000.0 // 射线检测时向上偏移的距离（确保起点在潜在地形之上） 默认100km);// 调用此函数来绘制或更新地表贴合线UFUNCTION(BlueprintCallable, Category = "Line Properties")void DrawSurfaceLine(TArray<FVector> SurfacePoints,FLinearColor LineColor = FLinearColor::Red, // 线的颜色float LineThickness = 10.0f // 线的粗细);//地心坐标UPROPERTY(EditAnywhere, BlueprintReadWrite)FVector EarthOrigin = FVector(0, 0, -637810000.0);protected:// Called when the game starts or when spawnedvirtual void BeginPlay() override;UPROPERTY(VisibleAnywhere, BlueprintReadOnly)ULineBatchComponent* LineBatchComponent;public: // Called every framevirtual void Tick(float DeltaTime) override;private:TArray<FVector> Points; //用于存储起点和终点连线之间的点
};
“SurfaceLineActor.cpp”
// Fill out your copyright notice in the Description page of Project Settings.#include "SurfaceLineActor.h"
#include "CesiumRuntime/Public/CesiumGeoreference.h"// Sets default values
ASurfaceLineActor::ASurfaceLineActor()
{// 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;PrimaryActorTick.bStartWithTickEnabled = true;LineBatchComponent = CreateDefaultSubobject<ULineBatchComponent>(TEXT("LineBatcher"));// 可以将 LineBatchComponent 设为根组件，或者附加到其他组件上RootComponent = LineBatchComponent;LineBatchComponent->bCalculateAccurateBounds = false; // Optimization for dynamic lines}// Called when the game starts or when spawned
void ASurfaceLineActor::BeginPlay()
{Super::BeginPlay();}// Called every frame
void ASurfaceLineActor::Tick(float DeltaTime)
{Super::Tick(DeltaTime);}void ASurfaceLineActor::DrawSurfaceLine(TArray<FVector> SurfacePoints, FLinearColor LineColor, float LineThickness)
{if (!LineBatchComponent){UE_LOG(LogTemp, Warning, TEXT("SurfaceLineActor: LineBatchComponent is null."));return;}LineBatchComponent->Flush(); // 清除之前的线if (SurfacePoints.Num() >= 2){for (int32 i = 0; i < SurfacePoints.Num() - 1; ++i){if (SurfacePoints[i].ContainsNaN() || SurfacePoints[i + 1].ContainsNaN()){UE_LOG(LogTemp, Warning, TEXT("SurfaceLineActor: Encountered NaN point at segment %d, skipping draw."), i);continue;}LineBatchComponent->DrawLine(SurfacePoints[i],SurfacePoints[i + 1],LineColor,SDPG_World, // 场景深度优先级组-根据渲染顺序需要进行调整LineThickness,0.0f // 线的生命周期时长：0表示无限生命);}}
}TArray<FVector> ASurfaceLineActor::CalculatePointsOnSurface(FVector StartPointLLA, FVector EndPointLLA, int32 NumberOfSegments, double TraceUpOffset)
{//将起点和终点拔高一段距离以方便往地心打射线StartPointLLA = StartPointLLA + FVector(0, 0, TraceUpOffset);EndPointLLA = EndPointLLA + FVector(0, 0, TraceUpOffset);//获取GeoreferenceACesiumGeoreference* Georeference = ACesiumGeoreference::GetDefaultGeoreference(GetWorld());if (!Georeference){UE_LOG(LogTemp, Warning, TEXT("SurfaceLineActor: CesiumGeoreference not found. Cannot calculate surface points."));}//将起终点（经纬高）转换为起终点（UE世界坐标）FVector StartPoint = Georeference->TransformLongitudeLatitudeHeightPositionToUnreal(StartPointLLA);FVector EndPoint = Georeference->TransformLongitudeLatitudeHeightPositionToUnreal(EndPointLLA);Points.Empty();if (NumberOfSegments <= 0) // 分段数不满足要求，返回起点和终点{// 如果段数无效，至少包含起点和终点Points.Add(StartPoint);if (StartPoint != EndPoint) // 避免重复添加同一点{Points.Add(EndPoint);}}else{//Points.Reserve(NumberOfSegments + 1); // 预分配空间提高效率for (int32 i = 0; i < NumberOfSegments; ++i){float T = static_cast<float>(i) / static_cast<float>(NumberOfSegments);FVector CurrentPoint = FMath::Lerp(StartPoint, EndPoint, T); // 使用 FMath::Lerp 进行线性插值计算点的坐标Points.Add(CurrentPoint);}Points.Add(EndPoint); //需要加上终点}// 用于存储射线检测到的地表点TArray<FVector> CalculatedSurfacePoints;//起点和终点构成的连线中每个点都朝地心发出射线for (int32 i = 0; i < Points.Num(); ++i){FHitResult HitResult;FCollisionQueryParams QueryParams;QueryParams.AddIgnoredActor(this); // 射线检测忽视自身//QueryParams.AddIgnoredActors(ActorsToIgnore); // 忽视射线检测的ActorQueryParams.bTraceComplex = true; // 使用复杂碰撞QueryParams.bReturnPhysicalMaterial = false; // 是否检测物理材料ECollisionChannel TraceChannel = ECC_Visibility;UWorld* World = GetWorld();bool bHit = World->LineTraceSingleByChannel(HitResult, // 射线检测结果Points[i], // 射线起点EarthOrigin, // 射线终点（地心）TraceChannel, // 射线碰撞通道QueryParams // 射线碰撞其他参数);画射线检测（非必需）//DrawDebugLine(// GetWorld(),// Points[i], //起点// EarthOrigin, //终点（地心）// bHit ? FColor::Green : FColor::Red, //颜色// false, // false表示它持续“LifeTime”，如果LifeTime为0，则持续一帧// 0.0, // DebugLine生命周期时长// 0, // DepthPriority (0 for SDPG_World)// 2.0f//);if (bHit){画射线碰撞点（非必需）//DrawDebugSphere(// GetWorld(),// HitResult.Location,// 30.0f, // Radius// 12, // Segments// FColor::Cyan,// false, // Persistent lines// 0.0f // Lifetime//);FVector OutHitLocation = HitResult.ImpactPoint;CalculatedSurfacePoints.Add(OutHitLocation);}}return CalculatedSurfacePoints;
}