blueprint viewport

选中组件后，有些模型会绘制一些标识，是通过 ComponentVisualizers.cpp 来实现的。

部分代码截取：

void FComponentVisualizersModule::StartupModule()
{
	RegisterComponentVisualizer(UPointLightComponent::StaticClass()->GetFName(), MakeShareable(new FPointLightComponentVisualizer));
	RegisterComponentVisualizer(USpotLightComponent::StaticClass()->GetFName(), MakeShareable(new FSpotLightComponentVisualizer));
	RegisterComponentVisualizer(URectLightComponent::StaticClass()->GetFName(), MakeShareable(new FRectLightComponentVisualizer));
	RegisterComponentVisualizer(UAudioComponent::StaticClass()->GetFName(), MakeShareable(new FAudioComponentVisualizer));
	RegisterComponentVisualizer(UForceFeedbackComponent::StaticClass()->GetFName(), MakeShareable(new FForceFeedbackComponentVisualizer));
	RegisterComponentVisualizer(URadialForceComponent::StaticClass()->GetFName(), MakeShareable(new FRadialForceComponentVisualizer));
	RegisterComponentVisualizer(UPhysicsConstraintComponent::StaticClass()->GetFName(), MakeShareable(new FConstraintComponentVisualizer));
	RegisterComponentVisualizer(UPhysicalAnimationComponent::StaticClass()->GetFName(), MakeShareable(new FPhysicsAnimationComponentVisualizer));
	RegisterComponentVisualizer(USpringArmComponent::StaticClass()->GetFName(), MakeShareable(new FSpringArmComponentVisualizer));
	RegisterComponentVisualizer(USplineComponent::StaticClass()->GetFName(), MakeShareable(new FSplineComponentVisualizer));
	RegisterComponentVisualizer(USplineMeshComponent::StaticClass()->GetFName(), MakeShareable(new FSplineMeshComponentVisualizer));
	RegisterComponentVisualizer(UPawnSensingComponent::StaticClass()->GetFName(), MakeShareable(new FSensingComponentVisualizer));
	RegisterComponentVisualizer(UPhysicsSpringComponent::StaticClass()->GetFName(), MakeShareable(new FSpringComponentVisualizer));
	RegisterComponentVisualizer(UDecalComponent::StaticClass()->GetFName(), MakeShareable(new FDecalComponentVisualizer));
	RegisterComponentVisualizer(UStereoLayerComponent::StaticClass()->GetFName(), MakeShareable(new FStereoLayerComponentVisualizer));
	RegisterComponentVisualizer(UWorldPartitionStreamingSourceComponent::StaticClass()->GetFName(), MakeShareable(new FWorldPartitionStreamingSourceComponentVisualizer));
	RegisterComponentVisualizer(ULocalFogVolumeComponent::StaticClass()->GetFName(), MakeShareable(new FLocalFogVolumeComponentVisualizer));
}

其中 sprintarm 的绘制实现：FSpringArmComponentVisualizer

static const FColor	ArmColor(255,0,0);

void FSpringArmComponentVisualizer::DrawVisualization(const UActorComponent* Component, const FSceneView* View, FPrimitiveDrawInterface* PDI)
{
	if (const USpringArmComponent* SpringArm = Cast<const USpringArmComponent>(Component))
	{
		PDI->DrawLine( SpringArm->GetComponentLocation(), SpringArm->GetSocketTransform(TEXT("SpringEndpoint"),RTS_World).GetTranslation(), ArmColor, SDPG_World );
	}
}