// Copyright Epic Games, Inc. All Rights Reserved. 

#include "AssetUtils/MeshDescriptionUtil.h"

#include "Engine/StaticMesh.h"
#include "Engine/Classes/Components/StaticMeshComponent.h"
#include "StaticMeshAttributes.h"
#include "StaticMeshOperations.h"




void UE::MeshDescription::InitializeAutoGeneratedAttributes(FMeshDescription& Mesh, const FMeshBuildSettings* BuildSettings)
{
	check(BuildSettings);

	// if the build settings don't indicate calculated normals/tangents, we will assume they are good
	if (BuildSettings->bRecomputeNormals || BuildSettings->bRecomputeTangents)
	{
		// check if any are invalid
		bool bHasInvalidNormals, bHasInvalidTangents;
		FStaticMeshOperations::AreNormalsAndTangentsValid(Mesh, bHasInvalidNormals, bHasInvalidTangents);

		// if neither are invalid we are not going to recompute
		if (bHasInvalidNormals || bHasInvalidTangents)
		{
			FStaticMeshAttributes Attributes(Mesh);
			if (!Attributes.GetTriangleNormals().IsValid() || !Attributes.GetTriangleTangents().IsValid())
			{
				// If these attributes don't exist, create them and compute their values for each triangle
				FStaticMeshOperations::ComputeTriangleTangentsAndNormals(Mesh);
			}

			EComputeNTBsFlags ComputeNTBsOptions = EComputeNTBsFlags::BlendOverlappingNormals;
			ComputeNTBsOptions |= BuildSettings->bRecomputeNormals ? EComputeNTBsFlags::Normals : EComputeNTBsFlags::None;
			ComputeNTBsOptions |= BuildSettings->bRecomputeTangents ? EComputeNTBsFlags::Tangents : EComputeNTBsFlags::None;
			ComputeNTBsOptions |= BuildSettings->bUseMikkTSpace ? EComputeNTBsFlags::UseMikkTSpace : EComputeNTBsFlags::None;
			ComputeNTBsOptions |= BuildSettings->bComputeWeightedNormals ? EComputeNTBsFlags::WeightedNTBs : EComputeNTBsFlags::None;
			ComputeNTBsOptions |= BuildSettings->bRemoveDegenerates ? EComputeNTBsFlags::IgnoreDegenerateTriangles : EComputeNTBsFlags::None;

			FStaticMeshOperations::ComputeTangentsAndNormals(Mesh, ComputeNTBsOptions);
		}
	}
}





void UE::MeshDescription::InitializeAutoGeneratedAttributes(FMeshDescription& Mesh, UStaticMesh* StaticMesh, int32 SourceLOD)
{
#if WITH_EDITOR
	if (ensureMsgf(SourceLOD < StaticMesh->GetNumSourceModels(), TEXT("InitializeMeshDescription requested LOD index greater than num available in UStaticMesh")))
	{
		const FStaticMeshSourceModel& SourceModel = StaticMesh->GetSourceModel(SourceLOD);
		InitializeAutoGeneratedAttributes(Mesh, &SourceModel.BuildSettings);
	}
#else
	ensureMsgf(false, TEXT("InitializeMeshDescription requires Editor-only SourceModel field of UStaticMesh"));
#endif
}



void UE::MeshDescription::InitializeAutoGeneratedAttributes(FMeshDescription& Mesh, UActorComponent* StaticMeshComponent, int32 SourceLOD)
{
#if WITH_EDITOR
	if (Cast<UStaticMeshComponent>(StaticMeshComponent) != nullptr)
	{
		UStaticMesh* StaticMesh = Cast<UStaticMeshComponent>(StaticMeshComponent)->GetStaticMesh();
		if (ensure(StaticMesh != nullptr))
		{
			InitializeAutoGeneratedAttributes(Mesh, StaticMesh, SourceLOD);
		}
	}
#else
	//ensureMsgf(false, TEXT("InitializeMeshDescription requires Editor-only SourceModel field of UStaticMesh"));
#endif
}



void UE::MeshDescription::ConfigureBuildSettings(UStaticMesh* StaticMesh, int32 SourceLOD, FStaticMeshBuildSettingChange NewSettings)
{
#if WITH_EDITOR
	if (ensureMsgf(SourceLOD < StaticMesh->GetNumSourceModels(), TEXT("ConfigureBuildSettings requested LOD index greater than num available in UStaticMesh")))
	{
		FStaticMeshSourceModel& SourceModel = StaticMesh->GetSourceModel(SourceLOD);
		
		if (NewSettings.AutoGeneratedNormals != EBuildSettingBoolChange::NoChange)
		{
			SourceModel.BuildSettings.bRecomputeNormals = 
				(NewSettings.AutoGeneratedNormals == EBuildSettingBoolChange::Disable) ? false : true;
		}
		if (NewSettings.AutoGeneratedTangents != EBuildSettingBoolChange::NoChange)
		{
			SourceModel.BuildSettings.bRecomputeTangents = 
				(NewSettings.AutoGeneratedTangents == EBuildSettingBoolChange::Disable) ? false : true;
		}
		if (NewSettings.UseMikkTSpaceTangents != EBuildSettingBoolChange::NoChange)
		{
			SourceModel.BuildSettings.bUseMikkTSpace = 
				(NewSettings.UseMikkTSpaceTangents == EBuildSettingBoolChange::Disable) ? false : true;
		}
	}
#else
	// just ignore?
#endif
}