assimp/code/AssetLib/DXF/DXFLoader.cpp

/*
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/** @file  DXFLoader.cpp
 *  @brief Implementation of the DXF importer class
 */


#ifndef ASSIMP_BUILD_NO_DXF_IMPORTER

#include "AssetLib/DXF/DXFLoader.h"
#include "AssetLib/DXF/DXFHelper.h"
#include "PostProcessing/ConvertToLHProcess.h"

#include <assimp/ParsingUtils.h>
#include <assimp/fast_atof.h>
#include <assimp/IOSystem.hpp>
#include <assimp/scene.h>
#include <assimp/importerdesc.h>

#include <numeric>

using namespace Assimp;

// AutoCAD Binary DXF<CR><LF><SUB><NULL>
static constexpr char AI_DXF_BINARY_IDENT[] = "AutoCAD Binary DXF\r\n\x1a";
static constexpr size_t AI_DXF_BINARY_IDENT_LEN = sizeof AI_DXF_BINARY_IDENT;

// default vertex color that all uncolored vertices will receive
static const aiColor4D AI_DXF_DEFAULT_COLOR(aiColor4D(0.6f, 0.6f, 0.6f, 0.6f));

// color indices for DXF - 16 are supported, the table is
// taken directly from the DXF spec.
static aiColor4D g_aclrDxfIndexColors[] = {
    aiColor4D (0.6f, 0.6f, 0.6f, 1.0f),
    aiColor4D (1.0f, 0.0f, 0.0f, 1.0f), // red
    aiColor4D (0.0f, 1.0f, 0.0f, 1.0f), // green
    aiColor4D (0.0f, 0.0f, 1.0f, 1.0f), // blue
    aiColor4D (0.3f, 1.0f, 0.3f, 1.0f), // light green
    aiColor4D (0.3f, 0.3f, 1.0f, 1.0f), // light blue
    aiColor4D (1.0f, 0.3f, 0.3f, 1.0f), // light red
    aiColor4D (1.0f, 0.0f, 1.0f, 1.0f), // pink
    aiColor4D (1.0f, 0.6f, 0.0f, 1.0f), // orange
    aiColor4D (0.6f, 0.3f, 0.0f, 1.0f), // dark orange
    aiColor4D (1.0f, 1.0f, 0.0f, 1.0f), // yellow
    aiColor4D (0.3f, 0.3f, 0.3f, 1.0f), // dark gray
    aiColor4D (0.8f, 0.8f, 0.8f, 1.0f), // light gray
    aiColor4D (0.0f, 00.f, 0.0f, 1.0f), // black
    aiColor4D (1.0f, 1.0f, 1.0f, 1.0f), // white
    aiColor4D (0.6f, 0.0f, 1.0f, 1.0f)  // violet
};
#define AI_DXF_NUM_INDEX_COLORS (sizeof(g_aclrDxfIndexColors)/sizeof(g_aclrDxfIndexColors[0]))
#define AI_DXF_ENTITIES_MAGIC_BLOCK "$ASSIMP_ENTITIES_MAGIC"

static const int GroupCode_Name  = 2;
static const int GroupCode_XComp = 10;
static const int GroupCode_YComp = 20;
static const int GroupCode_ZComp = 30;

static const aiImporterDesc desc = {
    "Drawing Interchange Format (DXF) Importer",
    "",
    "",
    "",
    aiImporterFlags_SupportTextFlavour | aiImporterFlags_LimitedSupport,
    0,
    0,
    0,
    0,
    "dxf"
};

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
DXFImporter::DXFImporter()
: BaseImporter() {
    // empty
}

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

// ------------------------------------------------------------------------------------------------
// Returns whether the class can handle the format of the given file.
bool DXFImporter::CanRead( const std::string& filename, IOSystem* pIOHandler, bool checkSig ) const {
    const std::string& extension = GetExtension( filename );
    if ( extension == desc.mFileExtensions ) {
        return true;
    }

    if ( extension.empty() || checkSig ) {
        static const char * const pTokens[] = { "SECTION", "HEADER", "ENDSEC", "BLOCKS" };
        return SearchFileHeaderForToken(pIOHandler, filename, pTokens, 4, 32 );
    }

    return false;
}

// ------------------------------------------------------------------------------------------------
// Get a list of all supported file extensions
const aiImporterDesc* DXFImporter::GetInfo () const {
    return &desc;
}

// ------------------------------------------------------------------------------------------------
// Imports the given file into the given scene structure.
void DXFImporter::InternReadFile( const std::string& filename, aiScene* pScene, IOSystem* pIOHandler) {
    std::shared_ptr<IOStream> file = std::shared_ptr<IOStream>( pIOHandler->Open( filename) );

    // Check whether we can read the file
    if( file.get() == nullptr ) {
        throw DeadlyImportError( "Failed to open DXF file ", filename, "");
    }

    // Check whether this is a binary DXF file - we can't read binary DXF files :-(
    char buff[AI_DXF_BINARY_IDENT_LEN] = {0};
    file->Read(buff,AI_DXF_BINARY_IDENT_LEN,1);

    if (0 == memcmp(AI_DXF_BINARY_IDENT,buff,AI_DXF_BINARY_IDENT_LEN)) {
        throw DeadlyImportError("DXF: Binary files are not supported at the moment");
    }

    // DXF files can grow very large, so read them via the StreamReader,
    // which will choose a suitable strategy.
    file->Seek(0,aiOrigin_SET);
    StreamReaderLE stream( file );

    DXF::LineReader reader (stream);
    DXF::FileData output;

    // now get all lines of the file and process top-level sections
    bool eof = false;
    while(!reader.End()) {

        // blocks table - these 'build blocks' are later (in ENTITIES)
        // referenced an included via INSERT statements.
        if (reader.Is(2,"BLOCKS")) {
            ParseBlocks(reader,output);
            continue;
        }

        // primary entity table
        if (reader.Is(2,"ENTITIES")) {
            ParseEntities(reader,output);
            continue;
        }

        // skip unneeded sections entirely to avoid any problems with them
        // altogether.
        else if (reader.Is(2,"CLASSES") || reader.Is(2,"TABLES")) {
            SkipSection(reader);
            continue;
        }

        else if (reader.Is(2,"HEADER")) {
            ParseHeader(reader,output);
            continue;
        }

        // comments
        else if (reader.Is(999)) {
            ASSIMP_LOG_INFO("DXF Comment: ", reader.Value());
        }

        // don't read past the official EOF sign
        else if (reader.Is(0,"EOF")) {
            eof = true;
            break;
        }

        ++reader;
    }
    if (!eof) {
        ASSIMP_LOG_WARN("DXF: EOF reached, but did not encounter DXF EOF marker");
    }

    ConvertMeshes(pScene,output);

    // Now rotate the whole scene by 90 degrees around the x axis to convert from AutoCAD's to Assimp's coordinate system
    pScene->mRootNode->mTransformation = aiMatrix4x4(
        1.f,0.f,0.f,0.f,
        0.f,0.f,1.f,0.f,
        0.f,-1.f,0.f,0.f,
        0.f,0.f,0.f,1.f) * pScene->mRootNode->mTransformation;
}

// ------------------------------------------------------------------------------------------------
void DXFImporter::ConvertMeshes(aiScene* pScene, DXF::FileData& output) {
    // the process of resolving all the INSERT statements can grow the
    // poly-count excessively, so log the original number.
    // XXX Option to import blocks as separate nodes?
    if (!DefaultLogger::isNullLogger()) {
        unsigned int vcount = 0, icount = 0;
        for (const DXF::Block& bl : output.blocks) {
            for (std::shared_ptr<const DXF::PolyLine> pl : bl.lines) {
                vcount += static_cast<unsigned int>(pl->positions.size());
                icount += static_cast<unsigned int>(pl->counts.size());
            }
        }

        ASSIMP_LOG_VERBOSE_DEBUG("DXF: Unexpanded polycount is ", icount, ", vertex count is ", vcount);
    }

    if (! output.blocks.size()  ) {
        throw DeadlyImportError("DXF: no data blocks loaded");
    }

    DXF::Block* entities( nullptr );

    // index blocks by name
    DXF::BlockMap blocks_by_name;
    for (DXF::Block& bl : output.blocks) {
        blocks_by_name[bl.name] = &bl;
        if ( !entities && bl.name == AI_DXF_ENTITIES_MAGIC_BLOCK ) {
            entities = &bl;
        }
    }

    if (!entities) {
        throw DeadlyImportError("DXF: no ENTITIES data block loaded");
    }

    typedef std::map<std::string, unsigned int> LayerMap;

    LayerMap layers;
    std::vector< std::vector< const DXF::PolyLine*> > corr;

    // now expand all block references in the primary ENTITIES block
    // XXX this involves heavy memory copying, consider a faster solution for future versions.
    ExpandBlockReferences(*entities,blocks_by_name);

    unsigned int cur = 0;
    for (std::shared_ptr<const DXF::PolyLine> pl : entities->lines) {
        if (pl->positions.size()) {

            std::map<std::string, unsigned int>::iterator it = layers.find(pl->layer);
            if (it == layers.end()) {
                ++pScene->mNumMeshes;

                layers[pl->layer] = cur++;

                std::vector< const DXF::PolyLine* > pv;
                pv.push_back(&*pl);

                corr.push_back(pv);
            }
            else {
                corr[(*it).second].push_back(&*pl);
            }
        }
    }

    if ( 0 == pScene->mNumMeshes) {
        throw DeadlyImportError("DXF: this file contains no 3d data");
    }

    pScene->mMeshes = new aiMesh*[ pScene->mNumMeshes ] ();

    for(const LayerMap::value_type& elem : layers){
        aiMesh* const mesh =  pScene->mMeshes[elem.second] = new aiMesh();
        mesh->mName.Set(elem.first);

        unsigned int cvert = 0,cface = 0;
        for(const DXF::PolyLine* pl : corr[elem.second]){
            // sum over all faces since we need to 'verbosify' them.
            cvert += std::accumulate(pl->counts.begin(),pl->counts.end(),0);
            cface += static_cast<unsigned int>(pl->counts.size());
        }

        aiVector3D* verts = mesh->mVertices = new aiVector3D[cvert];
        aiColor4D* colors = mesh->mColors[0] = new aiColor4D[cvert];
        aiFace* faces = mesh->mFaces = new aiFace[cface];

        mesh->mNumVertices = cvert;
        mesh->mNumFaces = cface;

        unsigned int prims = 0;
        unsigned int overall_indices = 0;
        for(const DXF::PolyLine* pl : corr[elem.second]){

            std::vector<unsigned int>::const_iterator it = pl->indices.begin();
            for(unsigned int facenumv : pl->counts) {
                aiFace& face = *faces++;
                face.mIndices = new unsigned int[face.mNumIndices = facenumv];

                for (unsigned int i = 0; i < facenumv; ++i) {
                    face.mIndices[i] = overall_indices++;

                    ai_assert(pl->positions.size() == pl->colors.size());
                    if (*it >= pl->positions.size()) {
                        throw DeadlyImportError("DXF: vertex index out of bounds");
                    }

                    *verts++ = pl->positions[*it];
                    *colors++ = pl->colors[*it++];
                }

                // set primitive flags now, this saves the extra pass in ScenePreprocessor.
                switch(face.mNumIndices) {
                    case 1:
                        prims |= aiPrimitiveType_POINT;
                        break;
                    case 2:
                        prims |= aiPrimitiveType_LINE;
                        break;
                    case 3:
                        prims |= aiPrimitiveType_TRIANGLE;
                        break;
                    default:
                        prims |= aiPrimitiveType_POLYGON;
                        break;
                }
            }
        }

        mesh->mPrimitiveTypes = prims;
        mesh->mMaterialIndex = 0;
    }

    GenerateHierarchy(pScene,output);
    GenerateMaterials(pScene,output);
}


// ------------------------------------------------------------------------------------------------
void DXFImporter::ExpandBlockReferences(DXF::Block& bl,const DXF::BlockMap& blocks_by_name) {
    for (const DXF::InsertBlock& insert : bl.insertions) {

        // first check if the referenced blocks exists ...
        const DXF::BlockMap::const_iterator it = blocks_by_name.find(insert.name);
        if (it == blocks_by_name.end()) {
            ASSIMP_LOG_ERROR("DXF: Failed to resolve block reference: ", insert.name,"; skipping" );
            continue;
        }

        // XXX this would be the place to implement recursive expansion if needed.
        const DXF::Block& bl_src = *(*it).second;

        for (std::shared_ptr<const DXF::PolyLine> pl_in : bl_src.lines) {
            if (!pl_in) {
                ASSIMP_LOG_ERROR("DXF: PolyLine instance is nullptr, skipping.");
                continue;
            }
            
            std::shared_ptr<DXF::PolyLine> pl_out = std::shared_ptr<DXF::PolyLine>(new DXF::PolyLine(*pl_in));

            if (bl_src.base.Length() || insert.scale.x!=1.f || insert.scale.y!=1.f || insert.scale.z!=1.f || insert.angle || insert.pos.Length()) {
                // manual coordinate system transformation
                // XXX order
                aiMatrix4x4 trafo, tmp;
                aiMatrix4x4::Translation(-bl_src.base,trafo);
                trafo *= aiMatrix4x4::Scaling(insert.scale,tmp);
                trafo *= aiMatrix4x4::Translation(insert.pos,tmp);

                // XXX rotation currently ignored - I didn't find an appropriate sample model.
                if (insert.angle != 0.f) {
                    ASSIMP_LOG_WARN("DXF: BLOCK rotation not currently implemented");
                }

                for (aiVector3D& v : pl_out->positions) {
                    v *= trafo;
                }
            }

            bl.lines.push_back(pl_out);
        }
    }
}

// ------------------------------------------------------------------------------------------------
void DXFImporter::GenerateMaterials(aiScene* pScene, DXF::FileData& /*output*/) {
    // generate an almost-white default material. Reason:
    // the default vertex color is GREY, so we are
    // already at Assimp's usual default color.
    // generate a default material
    aiMaterial* pcMat = new aiMaterial();
    aiString s;
    s.Set(AI_DEFAULT_MATERIAL_NAME);
    pcMat->AddProperty(&s, AI_MATKEY_NAME);

    aiColor4D clrDiffuse(0.9f,0.9f,0.9f,1.0f);
    pcMat->AddProperty(&clrDiffuse,1,AI_MATKEY_COLOR_DIFFUSE);

    clrDiffuse = aiColor4D(1.0f,1.0f,1.0f,1.0f);
    pcMat->AddProperty(&clrDiffuse,1,AI_MATKEY_COLOR_SPECULAR);

    clrDiffuse = aiColor4D(0.05f,0.05f,0.05f,1.0f);
    pcMat->AddProperty(&clrDiffuse,1,AI_MATKEY_COLOR_AMBIENT);

    pScene->mNumMaterials = 1;
    pScene->mMaterials = new aiMaterial*[1];
    pScene->mMaterials[0] = pcMat;
}

// ------------------------------------------------------------------------------------------------
void DXFImporter::GenerateHierarchy(aiScene* pScene, DXF::FileData& /*output*/) {
    // generate the output scene graph, which is just the root node with a single child for each layer.
    pScene->mRootNode = new aiNode();
    pScene->mRootNode->mName.Set("<DXF_ROOT>");

    if (1 == pScene->mNumMeshes)    {
        pScene->mRootNode->mMeshes = new unsigned int[ pScene->mRootNode->mNumMeshes = 1 ];
        pScene->mRootNode->mMeshes[0] = 0;
    } else {
        pScene->mRootNode->mChildren = new aiNode*[ pScene->mRootNode->mNumChildren = pScene->mNumMeshes ];
        for (unsigned int m = 0; m < pScene->mRootNode->mNumChildren;++m)   {
            aiNode* p = pScene->mRootNode->mChildren[m] = new aiNode();
            p->mName = pScene->mMeshes[m]->mName;

            p->mMeshes = new unsigned int[p->mNumMeshes = 1];
            p->mMeshes[0] = m;
            p->mParent = pScene->mRootNode;
        }
    }
}


// ------------------------------------------------------------------------------------------------
void DXFImporter::SkipSection(DXF::LineReader& reader) {
    for( ;!reader.End() && !reader.Is(0,"ENDSEC"); reader++);
}

// ------------------------------------------------------------------------------------------------
void DXFImporter::ParseHeader(DXF::LineReader& reader, DXF::FileData& ) {
    for( ;!reader.End() && !reader.Is(0,"ENDSEC"); reader++);
}

// ------------------------------------------------------------------------------------------------
void DXFImporter::ParseBlocks(DXF::LineReader& reader, DXF::FileData& output) {
    while( !reader.End() && !reader.Is(0,"ENDSEC")) {
        if (reader.Is(0,"BLOCK")) {
            ParseBlock(++reader,output);
            continue;
        }
        ++reader;
    }

    ASSIMP_LOG_VERBOSE_DEBUG("DXF: got ", output.blocks.size()," entries in BLOCKS" );
}

// ------------------------------------------------------------------------------------------------
void DXFImporter::ParseBlock(DXF::LineReader& reader, DXF::FileData& output) {
    // push a new block onto the stack.
    output.blocks.push_back( DXF::Block() );
    DXF::Block& block = output.blocks.back();

    while( !reader.End() && !reader.Is(0,"ENDBLK")) {

        switch(reader.GroupCode()) {
            case GroupCode_Name:
                block.name = reader.Value();
                break;

            case GroupCode_XComp:
                block.base.x = reader.ValueAsFloat();
                break;
            case GroupCode_YComp:
                block.base.y = reader.ValueAsFloat();
                break;
            case GroupCode_ZComp:
                block.base.z = reader.ValueAsFloat();
                break;
        }

        if (reader.Is(0,"POLYLINE")) {
            ParsePolyLine(++reader,output);
            continue;
        }

        // XXX is this a valid case?
        if (reader.Is(0,"INSERT")) {
            ASSIMP_LOG_WARN("DXF: INSERT within a BLOCK not currently supported; skipping");
            for( ;!reader.End() && !reader.Is(0,"ENDBLK"); ++reader);
            break;
        }

        else if (reader.Is(0,"3DFACE") || reader.Is(0,"LINE") || reader.Is(0,"3DLINE")) {
            //http://sourceforge.net/tracker/index.php?func=detail&aid=2970566&group_id=226462&atid=1067632
            Parse3DFace(++reader, output);
            continue;
        }
        ++reader;
    }
}

// ------------------------------------------------------------------------------------------------
void DXFImporter::ParseEntities(DXF::LineReader& reader, DXF::FileData& output) {
    // Push a new block onto the stack.
    output.blocks.push_back( DXF::Block() );
    DXF::Block& block = output.blocks.back();

    block.name = AI_DXF_ENTITIES_MAGIC_BLOCK;

    while( !reader.End() && !reader.Is(0,"ENDSEC")) {
        if (reader.Is(0,"POLYLINE")) {
            ParsePolyLine(++reader,output);
            continue;
        }

        else if (reader.Is(0,"INSERT")) {
            ParseInsertion(++reader,output);
            continue;
        }

        else if (reader.Is(0,"3DFACE") || reader.Is(0,"LINE") || reader.Is(0,"3DLINE")) {
            //http://sourceforge.net/tracker/index.php?func=detail&aid=2970566&group_id=226462&atid=1067632
            Parse3DFace(++reader, output);
            continue;
        }

        ++reader;
    }

    ASSIMP_LOG_VERBOSE_DEBUG( "DXF: got ", block.lines.size()," polylines and ", block.insertions.size(),
        " inserted blocks in ENTITIES" );
}

void DXFImporter::ParseInsertion(DXF::LineReader& reader, DXF::FileData& output) {
    output.blocks.back().insertions.push_back( DXF::InsertBlock() );
    DXF::InsertBlock& bl = output.blocks.back().insertions.back();

    while( !reader.End() && !reader.Is(0)) {
        switch(reader.GroupCode()) {
            // name of referenced block
        case GroupCode_Name:
            bl.name = reader.Value();
            break;

            // translation
        case GroupCode_XComp:
            bl.pos.x = reader.ValueAsFloat();
            break;
        case GroupCode_YComp:
            bl.pos.y = reader.ValueAsFloat();
            break;
        case GroupCode_ZComp:
            bl.pos.z = reader.ValueAsFloat();
            break;

            // scaling
        case 41:
            bl.scale.x = reader.ValueAsFloat();
            break;
        case 42:
            bl.scale.y = reader.ValueAsFloat();
            break;
        case 43:
            bl.scale.z = reader.ValueAsFloat();
            break;

            // rotation angle
        case 50:
            bl.angle = reader.ValueAsFloat();
            break;
        }
        reader++;
    }
}

#define DXF_POLYLINE_FLAG_CLOSED        0x1
#define DXF_POLYLINE_FLAG_3D_POLYLINE   0x8
#define DXF_POLYLINE_FLAG_3D_POLYMESH   0x10
#define DXF_POLYLINE_FLAG_POLYFACEMESH  0x40

// ------------------------------------------------------------------------------------------------
void DXFImporter::ParsePolyLine(DXF::LineReader& reader, DXF::FileData& output) {
    output.blocks.back().lines.push_back( std::shared_ptr<DXF::PolyLine>( new DXF::PolyLine() ) );
    DXF::PolyLine& line = *output.blocks.back().lines.back();

    unsigned int iguess = 0, vguess = 0;
    while( !reader.End() && !reader.Is(0,"ENDSEC")) {

        if (reader.Is(0,"VERTEX")) {
            ParsePolyLineVertex(++reader,line);
            if (reader.Is(0,"SEQEND")) {
                break;
            }
            continue;
        }

        switch(reader.GroupCode())
        {
        // flags --- important that we know whether it is a
        // polyface mesh or 'just' a line.
        case 70:
            if (!line.flags)    {
                line.flags = reader.ValueAsSignedInt();
            }
            break;

        // optional number of vertices
        case 71:
            vguess = reader.ValueAsSignedInt();
            line.positions.reserve(vguess);
            break;

        // optional number of faces
        case 72:
            iguess = reader.ValueAsSignedInt();
            line.indices.reserve(iguess);
            break;

        // 8 specifies the layer on which this line is placed on
        case 8:
            line.layer = reader.Value();
            break;
        }

        reader++;
    }

    //if (!(line.flags & DXF_POLYLINE_FLAG_POLYFACEMESH))   {
    //  DefaultLogger::get()->warn((Formatter::format("DXF: polyline not currently supported: "),line.flags));
    //  output.blocks.back().lines.pop_back();
    //  return;
    //}

    if (vguess && line.positions.size() != vguess) {
        ASSIMP_LOG_WARN("DXF: unexpected vertex count in polymesh: ",
            line.positions.size(),", expected ", vguess );
    }

    if (line.flags & DXF_POLYLINE_FLAG_POLYFACEMESH ) {
        if (line.positions.size() < 3 || line.indices.size() < 3)   {
            ASSIMP_LOG_WARN("DXF: not enough vertices for polymesh; ignoring");
            output.blocks.back().lines.pop_back();
            return;
        }

        // if these numbers are wrong, parsing might have gone wild.
        // however, the docs state that applications are not required
        // to set the 71 and 72 fields, respectively, to valid values.
        // So just fire a warning.
        if (iguess && line.counts.size() != iguess) {
            ASSIMP_LOG_WARN( "DXF: unexpected face count in polymesh: ", line.counts.size(),", expected ", iguess );
        }
    }
    else if (!line.indices.size() && !line.counts.size()) {
        // a poly-line - so there are no indices yet.
        size_t guess = line.positions.size() + (line.flags & DXF_POLYLINE_FLAG_CLOSED ? 1 : 0);
        line.indices.reserve(guess);

        line.counts.reserve(guess/2);
        for (unsigned int i = 0; i < line.positions.size()/2; ++i) {
            line.indices.push_back(i*2);
            line.indices.push_back(i*2+1);
            line.counts.push_back(2);
        }

        // closed polyline?
        if (line.flags & DXF_POLYLINE_FLAG_CLOSED) {
            line.indices.push_back(static_cast<unsigned int>(line.positions.size()-1));
            line.indices.push_back(0);
            line.counts.push_back(2);
        }
    }
}

#define DXF_VERTEX_FLAG_PART_OF_POLYFACE 0x80
#define DXF_VERTEX_FLAG_HAS_POSITIONS 0x40

// ------------------------------------------------------------------------------------------------
void DXFImporter::ParsePolyLineVertex(DXF::LineReader& reader, DXF::PolyLine& line) {
    unsigned int cnti = 0, flags = 0;
    unsigned int indices[4];

    aiVector3D out;
    aiColor4D clr = AI_DXF_DEFAULT_COLOR;

    while( !reader.End() ) {

        if (reader.Is(0)) { // SEQEND or another VERTEX
            break;
        }

        switch (reader.GroupCode()) {
        case 8:
                // layer to which the vertex belongs to - assume that
                // this is always the layer the top-level poly-line
                // entity resides on as well.
                if(reader.Value() != line.layer) {
                    ASSIMP_LOG_WARN("DXF: expected vertex to be part of a poly-face but the 0x128 flag isn't set");
                }
                break;

        case 70:
                flags = reader.ValueAsUnsignedInt();
                break;

        // VERTEX COORDINATES
        case GroupCode_XComp:
            out.x = reader.ValueAsFloat();
            break;

        case GroupCode_YComp:
            out.y = reader.ValueAsFloat();
            break;

        case GroupCode_ZComp:
            out.z = reader.ValueAsFloat();
            break;

        // POLYFACE vertex indices
        case 71:
        case 72:
        case 73:
        case 74:
            if (cnti == 4) {
                ASSIMP_LOG_WARN("DXF: more than 4 indices per face not supported; ignoring");
                break;
            }
            indices[cnti++] = reader.ValueAsUnsignedInt();
            break;

        // color
        case 62:
            clr = g_aclrDxfIndexColors[reader.ValueAsUnsignedInt() % AI_DXF_NUM_INDEX_COLORS];
            break;
        };

        reader++;
    }

    if (line.flags & DXF_POLYLINE_FLAG_POLYFACEMESH && !(flags & DXF_VERTEX_FLAG_PART_OF_POLYFACE)) {
        ASSIMP_LOG_WARN("DXF: expected vertex to be part of a polyface but the 0x128 flag isn't set");
    }

    if (cnti) {
        line.counts.push_back(cnti);
        for (unsigned int i = 0; i < cnti; ++i) {
            // IMPORTANT NOTE: POLYMESH indices are ONE-BASED
            if (indices[i] == 0) {
                ASSIMP_LOG_WARN("DXF: invalid vertex index, indices are one-based.");
                --line.counts.back();
                // Workaround to fix issue 2229
                if (line.counts.back() == 0) {
                    line.counts.pop_back();
                }
                continue;
            }
            line.indices.push_back(indices[i]-1);
        }
    } else {
        line.positions.push_back(out);
        line.colors.push_back(clr);
    }
}

// ------------------------------------------------------------------------------------------------
void DXFImporter::Parse3DFace(DXF::LineReader& reader, DXF::FileData& output)
{
    // (note) this is also used for for parsing line entities, so we
    // must handle the vertex_count == 2 case as well.

    output.blocks.back().lines.push_back( std::shared_ptr<DXF::PolyLine>( new DXF::PolyLine() )  );
    DXF::PolyLine& line = *output.blocks.back().lines.back();

    aiVector3D vip[4];
    aiColor4D  clr = AI_DXF_DEFAULT_COLOR;

    bool b[4] = {false,false,false,false};
    while( !reader.End() ) {

        // next entity with a groupcode == 0 is probably already the next vertex or polymesh entity
        if (reader.GroupCode() == 0) {
            break;
        }
        switch (reader.GroupCode())
        {

        // 8 specifies the layer
        case 8:
            line.layer = reader.Value();
            break;

        // x position of the first corner
        case 10:
            vip[0].x = reader.ValueAsFloat();
            b[2] = true;
            break;

        // y position of the first corner
        case 20:
            vip[0].y = reader.ValueAsFloat();
            b[2] = true;
            break;

        // z position of the first corner
        case 30:
            vip[0].z = reader.ValueAsFloat();
            b[2] = true;
            break;

        // x position of the second corner
        case 11:
            vip[1].x = reader.ValueAsFloat();
            b[3] = true;
            break;

        // y position of the second corner
        case 21:
            vip[1].y = reader.ValueAsFloat();
            b[3] = true;
            break;

        // z position of the second corner
        case 31:
            vip[1].z = reader.ValueAsFloat();
            b[3] = true;
            break;

        // x position of the third corner
        case 12:
            vip[2].x = reader.ValueAsFloat();
            b[0] = true;
            break;

        // y position of the third corner
        case 22:
            vip[2].y = reader.ValueAsFloat();
            b[0] = true;
            break;

        // z position of the third corner
        case 32:
            vip[2].z = reader.ValueAsFloat();
            b[0] = true;
            break;

        // x position of the fourth corner
        case 13:
            vip[3].x = reader.ValueAsFloat();
            b[1] = true;
            break;

        // y position of the fourth corner
        case 23:
            vip[3].y = reader.ValueAsFloat();
            b[1] = true;
            break;

        // z position of the fourth corner
        case 33:
            vip[3].z = reader.ValueAsFloat();
            b[1] = true;
            break;

        // color
        case 62:
            clr = g_aclrDxfIndexColors[reader.ValueAsUnsignedInt() % AI_DXF_NUM_INDEX_COLORS];
            break;
        };

        ++reader;
    }

    // the fourth corner may even be identical to the third,
    // in this case we treat it as if it didn't exist.
    if (vip[3] == vip[2]) {
        b[1] = false;
    }

    // sanity checks to see if we got something meaningful
    if ((b[1] && !b[0]) || !b[2] || !b[3]) {
        ASSIMP_LOG_WARN("DXF: unexpected vertex setup in 3DFACE/LINE/FACE entity; ignoring");
        output.blocks.back().lines.pop_back();
        return;
    }

    const unsigned int cnt = (2+(b[0]?1:0)+(b[1]?1:0));
    line.counts.push_back(cnt);

    for (unsigned int i = 0; i < cnt; ++i) {
        line.indices.push_back(static_cast<unsigned int>(line.positions.size()));
        line.positions.push_back(vip[i]);
        line.colors.push_back(clr);
    }
}

#endif // !! ASSIMP_BUILD_NO_DXF_IMPORTER