ue4-UDecalComponent组件，紧贴Mesh的材质

在4.11版本后的 TopDown 模板中，多了个紧跟光标移动的一个图案，会贴在不同凹凸面的Mesh中，就是使用了一个新增的组件 UDecalComponent

直接看 TopDown 模板中使用

c++ 中的 Character 中加个 UDecalComponent 组件

/** A decal that projects to the cursor location. */
UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category = Camera, meta = (AllowPrivateAccess = "true"))
class UDecalComponent* CursorToWorld;

//构造函数中加载一个蓝图材质set到 UDecalComponent 组件中
AMyTestCharacter::AMyTestCharacter()
{
// Create a decal in the world to show the cursor's location
CursorToWorld = CreateDefaultSubobject<UDecalComponent>("CursorToWorld");
CursorToWorld->SetupAttachment(RootComponent);
static ConstructorHelpers::FObjectFinder<UMaterial> DecalMaterialAsset(TEXT("Material'/Game/TopDownCPP/Blueprints/M_Cursor_Decal.M_Cursor_Decal'"));
if (DecalMaterialAsset.Succeeded())
{
CursorToWorld->SetDecalMaterial(DecalMaterialAsset.Object);
}
CursorToWorld->DecalSize = FVector(16.0f, 32.0f, 32.0f);
CursorToWorld->SetRelativeRotation(FRotator(90.0f, 0.0f, 0.0f).Quaternion());
}

蓝图子类可以对这个组件的 Decal Material 材质 进行重新赋值





每帧tick获取当前屏幕光标在当前摄像机对应 world 中的位置 Loaction，再将 UDecalComponent 组件set到那个 Location

void AMyTestCharacter::Tick(float DeltaSeconds)
{
Super::Tick(DeltaSeconds);
if (APlayerController* PC = Cast<APlayerController>(GetController()))
{
FHitResult TraceHitResult;
PC->GetHitResultUnderCursor(ECC_Visibility, true, TraceHitResult);
FVector CursorFV = TraceHitResult.ImpactNormal;
FRotator CursorR = CursorFV.Rotation();
CursorToWorld->SetWorldLocation(TraceHitResult.Location);
CursorToWorld->SetWorldRotation(CursorR);
}
}

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