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/** @file  OptimizeMeshes.cpp

 *  @brief Implementation of the aiProcess_OptimizeMeshes step

 */

#ifndef ASSIMP_BUILD_NO_OPTIMIZEMESHES_PROCESS

#include "OptimizeMeshes.h"

#include "ProcessHelper.h"

#include <assimp/SceneCombiner.h>

#include <assimp/Exceptional.h>

using namespace Assimp;

static const unsigned int NotSet   = 0xffffffff;

static const unsigned int DeadBeef = 0xdeadbeef;

// ------------------------------------------------------------------------------------------------

// Constructor to be privately used by Importer

OptimizeMeshesProcess::OptimizeMeshesProcess()

    : mScene()

    , pts(false)

    , max_verts( NotSet )

    , max_faces( NotSet ) {

    // empty

}

// ------------------------------------------------------------------------------------------------

// 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 ) ) ? DeadBeef : max_verts;

        return true;

    }

    return false;

}

// ------------------------------------------------------------------------------------------------

// Setup properties for the post-processing step

void OptimizeMeshesProcess::SetupProperties(const Importer* pImp)

{

    if( max_verts == DeadBeef /* 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) {

        ASSIMP_LOG_DEBUG("Skipping OptimizeMeshesProcess");

        return;

    }

    ASSIMP_LOG_DEBUG("OptimizeMeshesProcess begin");

    mScene = pScene;

    // need to clear persistent members from previous runs

    merge_list.resize( 0 );

    output.resize( 0 );

    // ensure we have the right sizes

    merge_list.reserve(pScene->mNumMeshes);

    output.reserve(pScene->mNumMeshes);

    // Prepare lookup tables

    meshes.resize(pScene->mNumMeshes);

    FindInstancedMeshes(pScene->mRootNode);

    if( max_verts == DeadBeef ) /* undo the magic hack */

        max_verts = NotSet;

    // ... 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 == NotSet ) {

            meshes[i].output_id = n++;

            output.push_back(mScene->mMeshes[i]);

        }

    }

    // and process all nodes in the scenegraph recursively

    ProcessNode(pScene->mRootNode);

    if (!output.size()) {

        throw DeadlyImportError("OptimizeMeshes: No meshes remaining; there's definitely something wrong");

    }

    meshes.resize( 0 );

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

    mScene->mNumMeshes = static_cast<unsigned int>(output.size());

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

    if (output.size() != num_old) {

        ASSIMP_LOG_DEBUG("OptimizeMeshesProcess finished. Input meshes: ", num_old, ", Output meshes: ", pScene->mNumMeshes);

    } else {

        ASSIMP_LOG_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.resize( 0 );

            unsigned int verts = 0, faces = 0;

            // Find meshes to merge with us

            for (unsigned int a = i+1; a < pNode->mNumMeshes;++a) {

                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->mMeshes[a] = pNode->mMeshes[pNode->mNumMeshes - 1];

                    --pNode->mNumMeshes;

                    --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 = static_cast<unsigned int>(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 ((NotSet != max_verts && verts+mb->mNumVertices > max_verts) ||

        (NotSet != 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 join them.

    if (ma->HasBones()) {

        // TODO

        return false;

    }

    return true;

}

// ------------------------------------------------------------------------------------------------

// Build 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