UE4:模型渲染流程

一.Custom Mesh

二.Procedural Mesh

public:
    AMyActor();

protected:
    virtual void BeginPlay() override;

    UPROPERTY(VisibleAnywhere, BlueprintReadWrite)
        UProceduralMeshComponent* CustomMesh;

    /* The vertices of the mesh */
    TArray<FVector> Vertices;

    /* The triangles of the mesh */
    TArray<int32> Triangles;

    /* Creates a triangle that connects the given vertices */
    void AddTriangle(int32 V1, int32 V2, int32 V3);

    void GenerateCubeMesh();

public:

    //Called every frame
    virtual void Tick(float DeltaTime) override;
        

//Sets default values
AMyActor::AMyActor()
{
    // Set this actor to call Tick() every frame. You can turn this off to
    PrimaryActorTick.bCanEverTick = true;

    CustomMesh = CreateDefaultSubobject<UProceduralMeshComponent>("CustomMesh");

    SetRootComponent(CustomMesh);
    CustomMesh->bUseAsyncCooking = true;
 
}

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

void AMyActor::AddTriangle(int32 V1, int32 V2, int32 V3)
{
    Triangles.Add(V1);
    Triangles.Add(V2);
    Triangles.Add(V3);
}

void AMyActor::GenerateCubeMesh()
{
    //6 sides on cube, 4 verts each(corners)
  
    //These are relative locations to the placed Actor in the world
    Vertices.Add(FVector(0, -100, 0));
    Vertices.Add(FVector(0, -100, 100));
    Vertices.Add(FVector(0, 100, 0));
    Vertices.Add(FVector(0, 100, 100));

    Vertices.Add(FVector(100, -100, 0));
    Vertices.Add(FVector(100, -100, 100));

    Vertices.Add(FVector(100, 100, 100));
    Vertices.Add(FVector(100, 100, 0));

    //Back face
    AddTriangle(0, 2, 3);
    AddTriangle(3, 1, 0);

    //Left face
    AddTriangle(0, 1, 4);
    AddTriangle(4, 1, 5);

    //Front face
    AddTriangle(4, 5, 7);
    AddTriangle(7, 5, 6);

    //Right face
    AddTriangle(7, 6, 3);
    AddTriangle(3, 2, 7);
 
    //Top face
    AddTriangle(1, 3, 5);
    AddTriangle(6, 5, 3);

    //bottom face
    AddTriangle(2, 0, 4);
    AddTrianlgle(4, 7, 2);

    TArray<FLinearColor> VertexColors;
    VertexColors.Add(FLinearColor(0.f, 0.f, 1.f));
    VertexColors.Add(FLinearColor(1.f, 0.f, 0.f));
    VertexColors.Add(FLinearColor(1.f, 0.f, 0.f));
    VertexColors.Add(FLinearColor(0.f, 1.f, 0.f));
    VertexColors.Add(FLinearColor(0.5f, 1.f, 0.5f));
    VertexColors.Add(FLinearColor(0.f, 1.f, 0.f));
    VertexColors.Add(FLinearColor(1.f, 1.f, 0.f));
    VertexColors.Add(FLinearColor(0.f, 1.f, 1.f));

    CustomMesh->CreateMeshSection_LinearColor(0, Vertices, Triangles, TArray<FVector>(),  TArray<FVector2D>(), VertexColors, TArray<FProcMeshTangent>(), true);

}

三.

UActorComponent

USceneComponent

UPrimitiveComponent

UMeshComponent

四.底层绘制

底层绘制模型的方式有两种：

UMeshComponent PrimitiveDrawInterface(PDI) 渲染模型
UPrimitiveComponent 渲染代理

//根据数组点创建几何体模型
UMeshComponent->PrimitiveDrawInterface->dynamicMesh
PDI->UStaticMeshComponent 
UStaticMesh->FRawMesh->FStaticMeshSourceModel->SaveRawMesh->Build

//底层绘制几何体模型
Primitive PrimitiveComponent

1.PrimitiveDrawInterface(PDI)