/*
---------------------------------------------------------------------------
Open Asset Import Library (ASSIMP)
---------------------------------------------------------------------------

Copyright (c) 2006-2008, ASSIMP Development Team

All rights reserved.

Redistribution and use of this software in source and binary forms, 
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* Redistributions of source code must retain the above
  copyright notice, this list of conditions and the
  following disclaimer.

* Redistributions in binary form must reproduce the above
  copyright notice, this list of conditions and the
  following disclaimer in the documentation and/or other
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* Neither the name of the ASSIMP team, nor the names of its
  contributors may be used to endorse or promote products
  derived from this software without specific prior
  written permission of the ASSIMP Development Team.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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*/

/** @file Implementation of the post processing step to generate face
* normals for all imported faces.
*/
#include "GenFaceNormalsProcess.h"
#include "DefaultLogger.h"
#include "../include/aiPostProcess.h"
#include "../include/aiMesh.h"
#include "../include/aiScene.h"

using namespace Assimp;

// Constructor to be privately used by Importer
GenFaceNormalsProcess::GenFaceNormalsProcess()
	{
	}

// Destructor, private as well
GenFaceNormalsProcess::~GenFaceNormalsProcess()
	{
	// nothing to do here
	}

// -------------------------------------------------------------------
// Returns whether the processing step is present in the given flag field.
bool GenFaceNormalsProcess::IsActive( unsigned int pFlags) const
{
	return	(pFlags & aiProcess_GenNormals) != 0;
}

// -------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void GenFaceNormalsProcess::Execute( aiScene* pScene)
{
	DefaultLogger::get()->debug("GenFaceNormalsProcess begin");

	bool bHas = false;
	for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
	{
		if(this->GenMeshFaceNormals( pScene->mMeshes[a]))
			bHas = true;
	}
	if (bHas)
	{
		DefaultLogger::get()->info("GenFaceNormalsProcess finished. "
			"Face normals have been calculated");
	}
	else DefaultLogger::get()->debug("GenFaceNormalsProcess finished. "
		"There was nothing to do");
}

// -------------------------------------------------------------------
// Executes the post processing step on the given imported data.
bool GenFaceNormalsProcess::GenMeshFaceNormals (aiMesh* pMesh)
{
	if (NULL != pMesh->mNormals)return false;

	pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];

	for( unsigned int a = 0; a < pMesh->mNumFaces; a++)
	{
		const aiFace& face = pMesh->mFaces[a];

		aiVector3D* pV1 = &pMesh->mVertices[face.mIndices[0]];
		aiVector3D* pV2 = &pMesh->mVertices[face.mIndices[1]];
		aiVector3D* pV3 = &pMesh->mVertices[face.mIndices[2]];

		aiVector3D pDelta1 = *pV2 - *pV1;
		aiVector3D pDelta2 = *pV3 - *pV1;
		aiVector3D vNor = pDelta1 ^ pDelta2;

		for (unsigned int i = 0;i < face.mNumIndices;++i)
		{
			pMesh->mNormals[face.mIndices[i]] = vNor;
		}
	}
	return true;
}