UE5.2、CesiumForUnreal实现加载GeoJson绘制单面

文章目录

前言
一、实现目标
二、实现过程
- 1.实现原理
- 2.数据读取
- 3.三角剖分
- 3.具体代码
4.蓝图测试

前言

UE5、CesiumForUnreal实现加载GeoJson绘制单面（Polygon）功能（StaticMesh方式）

一、实现目标

通过读取本地的Geojson数据，在UE中以staticMeshComponent的形式绘制出面数据，支持Editor和Runtime环境，如下图

singlePolygon

二、实现过程

1.实现原理

首先读取Geojson数据，然后进行三角剖分，最后根据顶点和索引创建StaticMesh。

2.数据读取

本文使用的是polygon转linestring格式的Geojson线状数据文件，特别需要注意，转完的数据需要去掉coordinates字段里的一组中括号。在UE中直接读取文本对其进行解析，生成坐标数组。本文数据只考虑一个feature情况，数据坐标格式为wgs84经纬度坐标。

例：{
“type”: “FeatureCollection”,
“name”: “singlePolygon”,
“crs”: { “type”: “name”, “properties”: { “name”: “urn:ogc:def:crs:OGC:1.3:CRS84” } },
“features”: [
{ “type”: “Feature”, “properties”: { “id”: 1 }, “geometry”: { “type”: “MultiLineString”, “coordinates”: [ [ 107.5955545517036, 34.322768426465544 ], [ 108.086216375377106, 34.660927250889173 ], [ 109.133845674571887, 34.448749164976306 ], [ 109.518418455288952, 33.261877996901205 ], [ 109.067540022724117, 32.552407522130054 ], [ 107.734796420583919, 32.738063347303815 ], [ 106.726950512497794, 32.930349737662347 ], [ 106.786625599160786, 33.792323211683374 ], [ 107.025325945812767, 33.938195645748472 ], [ 107.608815682073157, 34.322768426465544 ], [ 107.608815682073157, 34.322768426465544 ],[ 107.5955545517036, 34.322768426465544 ] ] } }
]
}

3.三角剖分

ue不支持直接绘制面，因此需要将面进行三角剖分。为快速的对地理控件点位进行三角剖分，直接使用Mapbox的earcut.hpp耳切算法三角剖分库。
地址：传送门

将其放到工程中的Source下的某个目录中，本文是放到了Developer文件夹中

Build.cs配置


using UnrealBuildTool;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;public class cesiumGeoJson : ModuleRules
{public cesiumGeoJson(ReadOnlyTargetRules Target) : base(Target){PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;//PublicIncludePaths.AddRange(new string[] { Path.Combine(ModuleDirectory, "./Source/Engine/Developer") });PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore" ,"CesiumRuntime","Json"});PrivateDependencyModuleNames.AddRange(new string[] {  });// Uncomment if you are using Slate UI// PrivateDependencyModuleNames.AddRange(new string[] { "Slate", "SlateCore" });// Uncomment if you are using online features// PrivateDependencyModuleNames.Add("OnlineSubsystem");// To include OnlineSubsystemSteam, add it to the plugins section in your uproject file with the Enabled attribute set to true}
}

3.具体代码

AsinglePolygon_Geojson.h

// Copyright 2020-2021 CesiumGS, Inc. and Contributors#pragma once#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "CesiumGeoreference.h"
#include "singlePolygon_Geojson.generated.h"UCLASS()
class CESIUMGEOJSON_API AsinglePolygon_Geojson : public AActor
{GENERATED_BODY()public:	// Sets default values for this actor's propertiesAsinglePolygon_Geojson();protected:// Called when the game starts or when spawnedvirtual void BeginPlay() override;public:	// Called every framevirtual void Tick(float DeltaTime) override;// Current world CesiumGeoreference.UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Entity | Polygon")ACesiumGeoreference* Georeference;// The selected feature index, current is only for '0', just for demo.UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Entity | Polygon");int SelectedFeatureIndex = 0;// The data path, that is the relative path of ue game content.UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Entity | Polygon");FString GeoJsonPath;/*** @breif Test generate polygon.*/UFUNCTION(CallInEditor, Category = "Entity | Polygon")void TestGeneratePolygon();/*** @brief Get feature vertices from linestring geojson.*/void GetCoordinatesFromLineStringGeoJson(const FString& FilePath, int FeatureIndex, TArray<FVector>& Positions);/*** @brief Build static polygon mesh component from current data.*/void BuildPolygonStaticMesh();private:// Verices that crs is unreal world.TArray<FVector> GeometryUE;// Vertices that crs is geographic wgs 84, epsg 4326.TArray<FVector> GeometryGeo;// Indices of vertices.TArray<uint32> Indices;};

AsinglePolygon_Geojson.cpp

// Copyright 2020-2021 CesiumGS, Inc. and Contributors#include "singlePolygon_Geojson.h"
#include "Kismet/KismetSystemLibrary.h"
#include "Engine/Developer/earcut.hpp"
#include "array"// Sets default values
AsinglePolygon_Geojson::AsinglePolygon_Geojson()
{// Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.PrimaryActorTick.bCanEverTick = false;}// Called when the game starts or when spawned
void AsinglePolygon_Geojson::BeginPlay()
{Super::BeginPlay();}// Called every frame
void AsinglePolygon_Geojson::Tick(float DeltaTime)
{Super::Tick(DeltaTime);}void AsinglePolygon_Geojson::TestGeneratePolygon()
{// Check file path and georeference is exist.if (!Georeference || GeoJsonPath.IsEmpty()){UE_LOG(LogTemp, Warning, TEXT("CesiumGeoreference or GeoJsonPath is valid, please check!"));return;}// Get the full path of file;FString FilePath = UKismetSystemLibrary::GetProjectDirectory() + GeoJsonPath;GetCoordinatesFromLineStringGeoJson(FilePath, 0, GeometryGeo);// First and last is the same point.GeometryGeo.Pop();// Triangulationstd::vector<std::vector<std::array<double, 2>>> Polygon;std::vector<std::array<double, 2>> Points;for (FVector& Item : GeometryGeo){std::array<double, 2> CurPoint = { Item.X, Item.Y };Points.push_back(CurPoint);// Convert coord from geo to ue.FVector PointUE = Georeference->TransformLongitudeLatitudeHeightPositionToUnreal(Item);GeometryUE.Push(PointUE);}// Current is just for simply polygon.Polygon.push_back(Points);std::vector<uint32_t> CalculateIndices = mapbox::earcut(Polygon);for (uint32_t Item : CalculateIndices){Indices.Push(Item);}// Build static mesh.BuildPolygonStaticMesh();
}void AsinglePolygon_Geojson::GetCoordinatesFromLineStringGeoJson(const FString& FilePath, int FeatureIndex, TArray<FVector>& Positions)
{// Check file exist.if (!FPaths::FileExists(FilePath)) {UE_LOG(LogTemp, Warning, TEXT("GeoJson file don't exist!"));return;}// ClearGeometryUE.Empty();GeometryGeo.Empty();Indices.Empty();FString FileString;FFileHelper::LoadFileToString(FileString, *FilePath);TSharedRef<TJsonReader<>> JsonReader = TJsonReaderFactory<>::Create(FileString);TSharedPtr<FJsonObject> Root;// Check deserializeif (!FJsonSerializer::Deserialize(JsonReader, Root)) {return;}if (Root->HasField(TEXT("features"))) {TArray<TSharedPtr<FJsonValue>> Features = Root->GetArrayField(TEXT("features"));// Check feature existif (Features.Num() < 1 || Features.Num() < (FeatureIndex + 1)) {return;}TSharedPtr<FJsonObject> Feature = Features[FeatureIndex]->AsObject();if (Feature->HasField(TEXT("geometry"))) {TSharedPtr<FJsonObject> Geometry = Feature->GetObjectField(TEXT("geometry"));if (Geometry->HasField(TEXT("coordinates"))) {TArray<TSharedPtr<FJsonValue>> Coordinates = Geometry->GetArrayField(TEXT("coordinates"));for (auto Item : Coordinates) {auto Coordinate = Item->AsArray();FVector Position;// Check coord array is 2 or 3.if (Coordinate.Num() == 2) {// If don't have z value, add target value for z.Position = FVector(Coordinate[0]->AsNumber(), Coordinate[1]->AsNumber(), 5000);}else if (Coordinate.Num() == 3){Position = FVector(Coordinate[0]->AsNumber(), Coordinate[1]->AsNumber(), Coordinate[2]->AsNumber());}Positions.Emplace(Position);}}}}
}void AsinglePolygon_Geojson::BuildPolygonStaticMesh()
{UStaticMeshComponent* pStaticMeshComponent = NewObject<UStaticMeshComponent>(this);pStaticMeshComponent->SetFlags(RF_Transient);pStaticMeshComponent->SetWorldLocationAndRotation(FVector(0, 0, 0), FRotator(0, 0, 0));UStaticMesh* pStaticMesh = NewObject<UStaticMesh>(pStaticMeshComponent);pStaticMesh->NeverStream = true;pStaticMeshComponent->SetStaticMesh(pStaticMesh);FStaticMeshRenderData* pRenderData = new FStaticMeshRenderData();pRenderData->AllocateLODResources(1);FStaticMeshLODResources& LODResourece = pRenderData->LODResources[0];TArray<FStaticMeshBuildVertex> StaticMeshBuildVertices;StaticMeshBuildVertices.SetNum(GeometryUE.Num());// Calculate boundsglm::dvec3 MinPosition{ std::numeric_limits<double>::max() };glm::dvec3 MaxPosition{ std::numeric_limits<double>::lowest() };// Verticesfor (int i = 0; i < GeometryUE.Num(); i++){FStaticMeshBuildVertex& Vertex = StaticMeshBuildVertices[i];Vertex.Position = FVector3f(GeometryUE[i]);Vertex.UVs[0] = FVector2f(0, 0);Vertex.TangentX = FVector3f(0, 1, 0);Vertex.TangentY = FVector3f(1, 0, 0);Vertex.TangentZ = FVector3f(0, 0, 1);// Calculate max and min position;MinPosition.x = glm::min<double>(MinPosition.x, GeometryUE[i].X);MinPosition.y = glm::min<double>(MinPosition.y, GeometryUE[i].Y);MinPosition.z = glm::min<double>(MinPosition.z, GeometryUE[i].Z);MaxPosition.x = glm::max<double>(MaxPosition.x, GeometryUE[i].X);MaxPosition.y = glm::max<double>(MaxPosition.y, GeometryUE[i].Y);MaxPosition.z = glm::max<double>(MaxPosition.z, GeometryUE[i].Z);}// Bounding boxFBox BoundingBox(FVector3d(MinPosition.x, MinPosition.y, MinPosition.z), FVector3d(MaxPosition.x, MaxPosition.y, MaxPosition.z));BoundingBox.GetCenterAndExtents(pRenderData->Bounds.Origin, pRenderData->Bounds.BoxExtent);LODResourece.bHasColorVertexData = false;LODResourece.VertexBuffers.PositionVertexBuffer.Init(StaticMeshBuildVertices);LODResourece.VertexBuffers.StaticMeshVertexBuffer.Init(StaticMeshBuildVertices, 1);LODResourece.IndexBuffer.SetIndices(Indices, EIndexBufferStride::AutoDetect);LODResourece.bHasDepthOnlyIndices = false;LODResourece.bHasReversedIndices = false;LODResourece.bHasReversedDepthOnlyIndices = false;FStaticMeshSectionArray& Sections = LODResourece.Sections;FStaticMeshSection& Section = Sections.AddDefaulted_GetRef();Section.bEnableCollision = true;Section.bCastShadow = true;Section.NumTriangles = Indices.Num() / 3;Section.FirstIndex = 0;Section.MinVertexIndex = 0;Section.MaxVertexIndex = Indices.Num() - 1;// Add materialUMaterialInterface* CurMaterial = LoadObject<UMaterialInterface>(nullptr, TEXT("Material'/Game/Martials/M_Polygon.M_Polygon'"));  //此处的材质需要手动在编辑器中创建，而后在c++代码中引用UMaterialInstanceDynamic* CurMaterialIns = UMaterialInstanceDynamic::Create(CurMaterial, nullptr);CurMaterialIns->AddToRoot();CurMaterialIns->TwoSided = true;FName CurMaterialSlotName = pStaticMesh->AddMaterial(CurMaterialIns);int32 CurMaterialIndex = pStaticMesh->GetMaterialIndex(CurMaterialSlotName);Section.MaterialIndex = CurMaterialIndex;// Todo:Build CollisionpStaticMesh->SetRenderData(TUniquePtr<FStaticMeshRenderData>(pRenderData));pStaticMesh->InitResources();pStaticMesh->CalculateExtendedBounds();pRenderData->ScreenSize[0].Default = 1.0f;pStaticMesh->CreateBodySetup();pStaticMeshComponent->SetMobility(EComponentMobility::Movable);pStaticMeshComponent->SetupAttachment(this->RootComponent);pStaticMeshComponent->RegisterComponent();
}