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/** @file  OptimizeMeshes.cpp
 *  @brief Implementation of the aiProcess_OptimizeMeshes step
 */

#include "AssimpPCH.h"
#ifndef ASSIMP_BUILD_NO_OPTIMIZEMESHES_PROCESS

using namespace Assimp;
#include "OptimizeMeshes.h"
#include "ProcessHelper.h"
#include "SceneCombiner.h"

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
OptimizeMeshesProcess::OptimizeMeshesProcess()
: pts (false)
, max_verts (0xffffffff)
, max_faces (0xffffffff)
{}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
OptimizeMeshesProcess::~OptimizeMeshesProcess()
{}

// ------------------------------------------------------------------------------------------------
// Returns whether the processing step is present in the given flag field.
bool OptimizeMeshesProcess::IsActive( unsigned int pFlags) const
{
	// Our behaviour needs to be different if the SortByPType or SplitLargeMeshes
	// steps are active. Thus we need to query their flags here and store the
	// information, although we're breaking const-correctness. 
	// That's a serious design flaw, consider redesign.
	if( 0 != (pFlags & aiProcess_OptimizeMeshes) ) {
		pts = (0 != (pFlags & aiProcess_SortByPType));
		max_verts = (0 != (pFlags & aiProcess_SplitLargeMeshes)) ? 0xdeadbeef : 0;
		return true;
	}
	return false;
}

// ------------------------------------------------------------------------------------------------
// Setup properties for the postprocessing step
void OptimizeMeshesProcess::SetupProperties(const Importer* pImp)
{
	if (max_verts == 0xdeadbeef /* magic hack */) {
		max_faces = pImp->GetPropertyInteger(AI_CONFIG_PP_SLM_TRIANGLE_LIMIT,AI_SLM_DEFAULT_MAX_TRIANGLES);
		max_verts = pImp->GetPropertyInteger(AI_CONFIG_PP_SLM_VERTEX_LIMIT,AI_SLM_DEFAULT_MAX_VERTICES);
	}
}

// ------------------------------------------------------------------------------------------------
// Execute step
void OptimizeMeshesProcess::Execute( aiScene* pScene)
{
	const unsigned int num_old = pScene->mNumMeshes;
	if (num_old <= 1) {
		DefaultLogger::get()->debug("Skipping OptimizeMeshesProcess");
		return;
	}

	DefaultLogger::get()->debug("OptimizeMeshesProcess begin");
	mScene = pScene;

	// need to clear persistent members from previous runs
	merge_list.clear();
	output.clear();

	merge_list.reserve(pScene->mNumMeshes);
	output.reserve(pScene->mNumMeshes);

	// Prepare lookup tables
	meshes.resize(pScene->mNumMeshes);
	FindInstancedMeshes(pScene->mRootNode);
	if (max_verts == 0xdeadbeef) /* undo the magic hack */
		max_verts = 0xffffffff;

	// ... instanced meshes are immediately processed and added to the output list
	for (unsigned int i = 0, n = 0; i < pScene->mNumMeshes;++i) {
		meshes[i].vertex_format = GetMeshVFormatUnique(pScene->mMeshes[i]);

		if (meshes[i].instance_cnt > 1 && meshes[i].output_id == 0xffffffff) {
			meshes[i].output_id = n++;
			output.push_back(mScene->mMeshes[i]);
		}
	}

	// and process all nodes in the scenegraoh recursively
	ProcessNode(pScene->mRootNode);
	if (!output.size()) {
		throw DeadlyImportError("OptimizeMeshes: No meshes remaining; there's definitely something wrong");
	}

	meshes.clear();
	ai_assert(output.size() <= num_old);

	mScene->mNumMeshes = output.size();
	std::copy(output.begin(),output.end(),mScene->mMeshes);

	if (output.size() != num_old) {
		char tmp[512];
		::sprintf(tmp,"OptimizeMeshesProcess finished. Input meshes: %i, Output meshes: %i",num_old,pScene->mNumMeshes);
		DefaultLogger::get()->info(tmp);
	}
	else DefaultLogger::get()->debug("OptimizeMeshesProcess finished");
}

// ------------------------------------------------------------------------------------------------
// Process meshes for a single node
void OptimizeMeshesProcess::ProcessNode( aiNode* pNode)
{
	for (unsigned int i = 0; i < pNode->mNumMeshes;++i) {
		unsigned int& im = pNode->mMeshes[i];

		if (meshes[im].instance_cnt > 1) {
			im = meshes[im].output_id;
		}
		else  {
			merge_list.clear();
			unsigned int verts = 0, faces = 0;

			// Find meshes to merge with us
			for (unsigned int a = i+1; a < pNode->mNumMeshes;++a) {
				register unsigned int am = pNode->mMeshes[a];
				if (meshes[am].instance_cnt == 1 && CanJoin(im,am,verts,faces)) {

					merge_list.push_back(mScene->mMeshes[am]);
					verts += mScene->mMeshes[am]->mNumVertices;
					faces += mScene->mMeshes[am]->mNumFaces;

					--pNode->mNumMeshes;
					for (unsigned int n = a; n < pNode->mNumMeshes; ++n)
						pNode->mMeshes[n] = pNode->mMeshes[n+1];

					--a;
				}
			}

			// and merge all meshes which we found, replace the old ones
			if (!merge_list.empty()) {
				merge_list.push_back(mScene->mMeshes[im]);

				aiMesh* out;
				SceneCombiner::MergeMeshes(&out,0,merge_list.begin(),merge_list.end());
				output.push_back(out);
			}
			else {
				output.push_back(mScene->mMeshes[im]);
			}
			im = output.size()-1;
		}
	}


	for (unsigned int i = 0; i < pNode->mNumChildren; ++i)
		ProcessNode(pNode->mChildren[i]);
}

// ------------------------------------------------------------------------------------------------
// Check whether two meshes can be joined
bool OptimizeMeshesProcess::CanJoin ( unsigned int a, unsigned int b, unsigned int verts, unsigned int faces )
{
	if (meshes[a].vertex_format != meshes[b].vertex_format)
		return false;

	aiMesh* ma = mScene->mMeshes[a], *mb = mScene->mMeshes[b];

	if ((0xffffffff != max_verts && verts+mb->mNumVertices > max_verts) ||
		(0xffffffff != max_faces && faces+mb->mNumFaces    > max_faces)) {
		return false;
	}

	// Never merge unskinned meshes with skinned meshes
	if (ma->mMaterialIndex != mb->mMaterialIndex || ma->HasBones() != mb->HasBones())
		return false;

	// Never merge meshes with different kinds of primitives if SortByPType did already
	// do its work. We would destroy everything again ...
	if (pts && ma->mPrimitiveTypes != mb->mPrimitiveTypes)
		return false;

	// If both meshes are skinned, check whether we have many bones defined in both meshes. 
	// If yes, we can savely join them. 
	if (ma->HasBones()) {
		// TODO
		return false;
	}
	return true;
}

// ------------------------------------------------------------------------------------------------
// Buidl a LUT of all instanced meshes
void OptimizeMeshesProcess::FindInstancedMeshes (aiNode* pNode)
{
	for (unsigned int i = 0; i < pNode->mNumMeshes;++i)
		++meshes[pNode->mMeshes[i]].instance_cnt; 

	for (unsigned int i = 0; i < pNode->mNumChildren; ++i)
		FindInstancedMeshes(pNode->mChildren[i]);
}

#endif // !! ASSIMP_BUILD_NO_OPTIMIZEMESHES_PROCESS
