axmol/cocos/3d/CCObjLoader.cpp

//
// Copyright 2012-2015, Syoyo Fujita.
//
// Licensed under 2-clause BSD license.
//

//
// version 0.9.13: Report "Material file not found message" in `err`(#46)
// version 0.9.12: Fix groups being ignored if they have 'usemtl' just before 'g' (#44)
// version 0.9.11: Invert `Tr` parameter(#43)
// version 0.9.10: Fix seg fault on windows.
// version 0.9.9 : Replace atof() with custom parser.
// version 0.9.8 : Fix multi-materials(per-face material ID).
// version 0.9.7 : Support multi-materials(per-face material ID) per
// object/group.
// version 0.9.6 : Support Ni(index of refraction) mtl parameter.
//                 Parse transmittance material parameter correctly.
// version 0.9.5 : Parse multiple group name.
//                 Add support of specifying the base path to load material file.
// version 0.9.4 : Initial support of group tag(g)
// version 0.9.3 : Fix parsing triple 'x/y/z'
// version 0.9.2 : Add more .mtl load support
// version 0.9.1 : Add initial .mtl load support
// version 0.9.0 : Initial
//

#include <cstdlib>
#include <cstring>
#include <cassert>
#include <cmath>
#include <cstddef>

#include <string>
#include <vector>
#include <map>
#include <fstream>
#include <sstream>
#include "platform/CCFileUtils.h"
#include "base/ccUtils.h"

#include "3d/CCObjLoader.h"

namespace tinyobj {
    
#define TINYOBJ_SSCANF_BUFFER_SIZE  (4096)
    
    struct vertex_index {
        int v_idx, vt_idx, vn_idx;
        vertex_index(){};
        vertex_index(int idx) : v_idx(idx), vt_idx(idx), vn_idx(idx){};
        vertex_index(int vidx, int vtidx, int vnidx)
        : v_idx(vidx), vt_idx(vtidx), vn_idx(vnidx){};
    };
    // for std::map
    static inline bool operator<(const vertex_index &a, const vertex_index &b) {
        if (a.v_idx != b.v_idx)
            return (a.v_idx < b.v_idx);
        if (a.vn_idx != b.vn_idx)
            return (a.vn_idx < b.vn_idx);
        if (a.vt_idx != b.vt_idx)
            return (a.vt_idx < b.vt_idx);
        
        return false;
    }
    
    struct obj_shape {
        std::vector<float> v;
        std::vector<float> vn;
        std::vector<float> vt;
    };
    
    static inline bool isSpace(const char c) { return (c == ' ') || (c == '\t'); }
    
    static inline bool isNewLine(const char c) {
        return (c == '\r') || (c == '\n') || (c == '\0');
    }
    
    // Make index zero-base, and also support relative index.
    static inline int fixIndex(int idx, int n) {
        if (idx > 0) return idx - 1;
        if (idx == 0) return 0;
        return n + idx; // negative value = relative
    }
    
    static inline std::string parseString(const char *&token) {
        std::string s;
        token += strspn(token, " \t");
        size_t e = strcspn(token, " \t\r");
        s = std::string(token, &token[e]);
        token += e;
        return s;
    }
    
    static inline int parseInt(const char *&token) {
        token += strspn(token, " \t");
        int i = atoi(token);
        token += strcspn(token, " \t\r");
        return i;
    }
    
    
    // Tries to parse a floating point number located at s.
    //
    // s_end should be a location in the string where reading should absolutely
    // stop. For example at the end of the string, to prevent buffer overflows.
    //
    // Parses the following EBNF grammar:
    //   sign    = "+" | "-" ;
    //   END     = ? anything not in digit ?
    //   digit   = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;
    //   integer = [sign] , digit , {digit} ;
    //   decimal = integer , ["." , integer] ;
    //   float   = ( decimal , END ) | ( decimal , ("E" | "e") , integer , END ) ;
    //
    //  Valid strings are for example:
    //   -0	 +3.1417e+2  -0.0E-3  1.0324  -1.41   11e2
    //
    // If the parsing is a success, result is set to the parsed value and true
    // is returned.
    //
    // The function is greedy and will parse until any of the following happens:
    //  - a non-conforming character is encountered.
    //  - s_end is reached.
    //
    // The following situations triggers a failure:
    //  - s >= s_end.
    //  - parse failure.
    //
    static bool tryParseDouble(const char *s, const char *s_end, double *result)
    {
        if (s >= s_end)
        {
            return false;
        }
        
        double mantissa = 0.0;
        // This exponent is base 2 rather than 10.
        // However the exponent we parse is supposed to be one of ten,
        // thus we must take care to convert the exponent/and or the
        // mantissa to a * 2^E, where a is the mantissa and E is the
        // exponent.
        // To get the final double we will use ldexp, it requires the
        // exponent to be in base 2.
        int exponent = 0;
        
        // NOTE: THESE MUST BE DECLARED HERE SINCE WE ARE NOT ALLOWED
        // TO JUMP OVER DEFINITIONS.
        char sign = '+';
        char exp_sign = '+';
        char const *curr = s;
        
        // How many characters were read in a loop.
        int read = 0;
        // Tells whether a loop terminated due to reaching s_end.
        bool end_not_reached = false;
        
        /*
         BEGIN PARSING.
         */
        
        // Find out what sign we've got.
        if (*curr == '+' || *curr == '-')
        {
            sign = *curr;
            curr++;
        }
        else if (isdigit(*curr)) { /* Pass through. */ }
        else
        {
            goto fail;
        }
        
        // Read the integer part.
        while ((end_not_reached = (curr != s_end)) && isdigit(*curr))
        {
            mantissa *= 10;
            mantissa += static_cast<int>(*curr - 0x30);
            curr++;	read++;
        }
        
        // We must make sure we actually got something.
        if (read == 0)
            goto fail;
        // We allow numbers of form "#", "###" etc.
        if (!end_not_reached)
            goto assemble;
        
        // Read the decimal part.
        if (*curr == '.')
        {
            curr++;
            read = 1;
            while ((end_not_reached = (curr != s_end)) && isdigit(*curr))
            {
                // NOTE: Don't use powf here, it will absolutely murder precision.
                mantissa += static_cast<int>(*curr - 0x30) * pow(10.0, -read);
                read++; curr++;
            }
        }
        else if (*curr == 'e' || *curr == 'E') {}
        else
        {
            goto assemble;
        }
        
        if (!end_not_reached)
            goto assemble;
        
        // Read the exponent part.
        if (*curr == 'e' || *curr == 'E')
        {
            curr++;
            // Figure out if a sign is present and if it is.
            if ((end_not_reached = (curr != s_end)) && (*curr == '+' || *curr == '-'))
            {
                exp_sign = *curr;
                curr++;
            }
            else if (isdigit(*curr)) { /* Pass through. */ }
            else
            {
                // Empty E is not allowed.
                goto fail;
            }
            
            read = 0;
            while ((end_not_reached = (curr != s_end)) && isdigit(*curr))
            {
                exponent *= 10;
                exponent += static_cast<int>(*curr - 0x30);
                curr++;	read++;
            }
            exponent *= (exp_sign == '+'? 1 : -1);
            if (read == 0)
                goto fail;
        }
        
    assemble:
        *result = (sign == '+'? 1 : -1) * ldexp(mantissa * pow(5.0, exponent), exponent);
        return true;
    fail:
        return false;
    }
    static inline float parseFloat(const char *&token) {
        token += strspn(token, " \t");
#ifdef TINY_OBJ_LOADER_OLD_FLOAT_PARSER
        float f = (float)utils::atof(token);
        token += strcspn(token, " \t\r");
#else
        const char *end = token + strcspn(token, " \t\r");
        double val = 0.0;
        tryParseDouble(token, end, &val);
        float f = static_cast<float>(val);
        token = end;
#endif
        return f;
    }
    
    
    static inline void parseFloat2(float &x, float &y, const char *&token) {
        x = parseFloat(token);
        y = parseFloat(token);
    }
    
    static inline void parseFloat3(float &x, float &y, float &z,
                                   const char *&token) {
        x = parseFloat(token);
        y = parseFloat(token);
        z = parseFloat(token);
    }
    
    // Parse triples: i, i/j/k, i//k, i/j
    static vertex_index parseTriple(const char *&token, int vsize, int vnsize,
                                    int vtsize) {
        vertex_index vi(-1);
        
        vi.v_idx = fixIndex(atoi(token), vsize);
        token += strcspn(token, "/ \t\r");
        if (token[0] != '/') {
            return vi;
        }
        token++;
        
        // i//k
        if (token[0] == '/') {
            token++;
            vi.vn_idx = fixIndex(atoi(token), vnsize);
            token += strcspn(token, "/ \t\r");
            return vi;
        }
        
        // i/j/k or i/j
        vi.vt_idx = fixIndex(atoi(token), vtsize);
        token += strcspn(token, "/ \t\r");
        if (token[0] != '/') {
            return vi;
        }
        
        // i/j/k
        token++; // skip '/'
        vi.vn_idx = fixIndex(atoi(token), vnsize);
        token += strcspn(token, "/ \t\r");
        return vi;
    }
    
    static unsigned int
    updateVertex(std::map<vertex_index, unsigned int> &vertexCache,
                 std::vector<float> &positions, std::vector<float> &normals,
                 std::vector<float> &texcoords,
                 const std::vector<float> &in_positions,
                 const std::vector<float> &in_normals,
                 const std::vector<float> &in_texcoords, const vertex_index &i) {
        const std::map<vertex_index, unsigned int>::iterator it = vertexCache.find(i);
        
        if (it != vertexCache.end()) {
            // found cache
            return it->second;
        }
        
        assert(in_positions.size() > (unsigned int)(3 * i.v_idx + 2));
        
        positions.push_back(in_positions[3 * i.v_idx + 0]);
        positions.push_back(in_positions[3 * i.v_idx + 1]);
        positions.push_back(in_positions[3 * i.v_idx + 2]);
        
        if (i.vn_idx >= 0) {
            normals.push_back(in_normals[3 * i.vn_idx + 0]);
            normals.push_back(in_normals[3 * i.vn_idx + 1]);
            normals.push_back(in_normals[3 * i.vn_idx + 2]);
        }
        
        if (i.vt_idx >= 0) {
            texcoords.push_back(in_texcoords[2 * i.vt_idx + 0]);
            texcoords.push_back(in_texcoords[2 * i.vt_idx + 1]);
        }
        
        unsigned int idx = static_cast<unsigned int>(positions.size() / 3 - 1);
        vertexCache[i] = idx;
        
        return idx;
    }
    
    void InitMaterial(material_t &material) {
        material.name = "";
        material.ambient_texname = "";
        material.diffuse_texname = "";
        material.specular_texname = "";
        material.normal_texname = "";
        for (int i = 0; i < 3; i++) {
            material.ambient[i] = 0.f;
            material.diffuse[i] = 0.f;
            material.specular[i] = 0.f;
            material.transmittance[i] = 0.f;
            material.emission[i] = 0.f;
        }
        material.illum = 0;
        material.dissolve = 1.f;
        material.shininess = 1.f;
        material.ior = 1.f;
        material.unknown_parameter.clear();
    }
    
    static bool exportFaceGroupToShape(
                                       shape_t &shape, std::map<vertex_index, unsigned int> vertexCache,
                                       const std::vector<float> &in_positions,
                                       const std::vector<float> &in_normals,
                                       const std::vector<float> &in_texcoords,
                                       const std::vector<std::vector<vertex_index> > &faceGroup,
                                       const int material_id, const std::string &name, bool clearCache) {
        if (faceGroup.empty()) {
            return false;
        }
        
        // Flatten vertices and indices
        for (size_t i = 0; i < faceGroup.size(); i++) {
            const std::vector<vertex_index> &face = faceGroup[i];
            
            vertex_index i0 = face[0];
            vertex_index i1(-1);
            vertex_index i2 = face[1];
            
            size_t npolys = face.size();
            
            // Polygon -> triangle fan conversion
            for (size_t k = 2; k < npolys; k++) {
                i1 = i2;
                i2 = face[k];
                
                unsigned int v0 = updateVertex(
                                               vertexCache, shape.mesh.positions, shape.mesh.normals,
                                               shape.mesh.texcoords, in_positions, in_normals, in_texcoords, i0);
                unsigned int v1 = updateVertex(
                                               vertexCache, shape.mesh.positions, shape.mesh.normals,
                                               shape.mesh.texcoords, in_positions, in_normals, in_texcoords, i1);
                unsigned int v2 = updateVertex(
                                               vertexCache, shape.mesh.positions, shape.mesh.normals,
                                               shape.mesh.texcoords, in_positions, in_normals, in_texcoords, i2);
                
                shape.mesh.indices.push_back(v0);
                shape.mesh.indices.push_back(v1);
                shape.mesh.indices.push_back(v2);
                
                shape.mesh.material_ids.push_back(material_id);
            }
        }
        
        shape.name = name;
        
        if (clearCache)
            vertexCache.clear();
        
        return true;
    }
    
    static std::string& replacePathSeperator(std::string& path)
    {
        for (std::string::size_type i = 0; i < path.size(); i++) {
            if (path[i] == '\\')
                path[i] = '/';
        }
        return path;
    }
    
    std::string LoadMtl(std::map<std::string, int> &material_map,
                        std::vector<material_t> &materials,
                        std::istream &inStream) {
        std::stringstream err;
        
        // Create a default material anyway.
        material_t material;
        InitMaterial(material);
        
        int maxchars = 8192;             // Alloc enough size.
        std::vector<char> buf(maxchars); // Alloc enough size.
        while (inStream.peek() != -1) {
            inStream.getline(&buf[0], maxchars);
            
            std::string linebuf(&buf[0]);
            
            // Trim newline '\r\n' or '\n'
            if (linebuf.size() > 0) {
                if (linebuf[linebuf.size() - 1] == '\n')
                    linebuf.erase(linebuf.size() - 1);
            }
            if (linebuf.size() > 0) {
                if (linebuf[linebuf.size() - 1] == '\r')
                    linebuf.erase(linebuf.size() - 1);
            }
            
            // Skip if empty line.
            if (linebuf.empty()) {
                continue;
            }
            
            // Skip leading space.
            const char *token = linebuf.c_str();
            token += strspn(token, " \t");
            
            assert(token);
            if (token[0] == '\0')
                continue; // empty line
            
            if (token[0] == '#')
                continue; // comment line
            
            // new mtl
            if ((0 == strncmp(token, "newmtl", 6)) && isSpace((token[6]))) {
                // flush previous material.
                if (!material.name.empty()) {
                    material_map.insert(
                                        std::pair<std::string, int>(material.name, static_cast<int>(materials.size())));
                    materials.push_back(material);
                }
                
                // initial temporary material
                InitMaterial(material);
                
                // set new mtl name
                char namebuf[TINYOBJ_SSCANF_BUFFER_SIZE];
                token += 7;
#ifdef _MSC_VER
                sscanf_s(token, "%s", namebuf, _countof(namebuf));
#else
                sscanf(token, "%s", namebuf);
#endif
                material.name = namebuf;
                continue;
            }
            
            // ambient
            if (token[0] == 'K' && token[1] == 'a' && isSpace((token[2]))) {
                token += 2;
                float r, g, b;
                parseFloat3(r, g, b, token);
                material.ambient[0] = r;
                material.ambient[1] = g;
                material.ambient[2] = b;
                continue;
            }
            
            // diffuse
            if (token[0] == 'K' && token[1] == 'd' && isSpace((token[2]))) {
                token += 2;
                float r, g, b;
                parseFloat3(r, g, b, token);
                material.diffuse[0] = r;
                material.diffuse[1] = g;
                material.diffuse[2] = b;
                continue;
            }
            
            // specular
            if (token[0] == 'K' && token[1] == 's' && isSpace((token[2]))) {
                token += 2;
                float r, g, b;
                parseFloat3(r, g, b, token);
                material.specular[0] = r;
                material.specular[1] = g;
                material.specular[2] = b;
                continue;
            }
            
            // transmittance
            if (token[0] == 'K' && token[1] == 't' && isSpace((token[2]))) {
                token += 2;
                float r, g, b;
                parseFloat3(r, g, b, token);
                material.transmittance[0] = r;
                material.transmittance[1] = g;
                material.transmittance[2] = b;
                continue;
            }
            
            // ior(index of refraction)
            if (token[0] == 'N' && token[1] == 'i' && isSpace((token[2]))) {
                token += 2;
                material.ior = parseFloat(token);
                continue;
            }
            
            // emission
            if (token[0] == 'K' && token[1] == 'e' && isSpace(token[2])) {
                token += 2;
                float r, g, b;
                parseFloat3(r, g, b, token);
                material.emission[0] = r;
                material.emission[1] = g;
                material.emission[2] = b;
                continue;
            }
            
            // shininess
            if (token[0] == 'N' && token[1] == 's' && isSpace(token[2])) {
                token += 2;
                material.shininess = parseFloat(token);
                continue;
            }
            
            // illum model
            if (0 == strncmp(token, "illum", 5) && isSpace(token[5])) {
                token += 6;
                material.illum = parseInt(token);
                continue;
            }
            
            // dissolve
            if ((token[0] == 'd' && isSpace(token[1]))) {
                token += 1;
                material.dissolve = parseFloat(token);
                continue;
            }
            if (token[0] == 'T' && token[1] == 'r' && isSpace(token[2])) {
                token += 2;
                // Invert value of Tr(assume Tr is in range [0, 1])
                material.dissolve = 1.0 - parseFloat(token);
                continue;
            }
            
            // ambient texture
            if ((0 == strncmp(token, "map_Ka", 6)) && isSpace(token[6])) {
                token += 7;
                material.ambient_texname = token;
                replacePathSeperator(material.ambient_texname);
                continue;
            }
            
            // diffuse texture
            if ((0 == strncmp(token, "map_Kd", 6)) && isSpace(token[6])) {
                token += 7;
                material.diffuse_texname = token;
                replacePathSeperator(material.diffuse_texname);
                continue;
            }
            
            // specular texture
            if ((0 == strncmp(token, "map_Ks", 6)) && isSpace(token[6])) {
                token += 7;
                material.specular_texname = token;
                replacePathSeperator(material.specular_texname);
                continue;
            }
            
            // normal texture
            if ((0 == strncmp(token, "map_Ns", 6)) && isSpace(token[6])) {
                token += 7;
                material.normal_texname = token;
                replacePathSeperator(material.normal_texname);
                continue;
            }
            
            // unknown parameter
            const char *_space = strchr(token, ' ');
            if (!_space) {
                _space = strchr(token, '\t');
            }
            if (_space) {
                std::ptrdiff_t len = _space - token;
                std::string key(token, len);
                std::string value = _space + 1;
                material.unknown_parameter.insert(
                                                  std::pair<std::string, std::string>(key, value));
            }
        }
        // flush last material.
        material_map.insert(
                            std::pair<std::string, int>(material.name, static_cast<int>(materials.size())));
        materials.push_back(material);
        
        return err.str();
    }
    
    std::string MaterialFileReader::operator()(const std::string &matId,
                                               std::vector<material_t> &materials,
                                               std::map<std::string, int> &matMap) {
        std::string filepath;
        
        if (!m_mtlBasePath.empty()) {
            filepath = std::string(m_mtlBasePath) + matId;
        } else {
            filepath = matId;
        }
        
        std::istringstream matIStream(cocos2d::FileUtils::getInstance()->getStringFromFile(filepath));
        std::string err = LoadMtl(matMap, materials, matIStream);
        if (!matIStream) {
            std::stringstream ss;
            ss << "WARN: Material file [ " << filepath << " ] not found. Created a default material.";
            err += ss.str();
        }
        return err;
    }
    
    std::string LoadObj(std::vector<shape_t> &shapes,
                        std::vector<material_t> &materials, // [output]
                        const char *filename, const char *mtl_basepath) {
        
        shapes.clear();
        
        std::stringstream err;
        
        std::istringstream ifs(cocos2d::FileUtils::getInstance()->getStringFromFile(filename));
        if (!ifs) {
            err << "Cannot open file [" << filename << "]" << std::endl;
            return err.str();
        }
        
        std::string basePath;
        if (mtl_basepath) {
            basePath = mtl_basepath;
        }
        MaterialFileReader matFileReader(basePath);
        
        return LoadObj(shapes, materials, ifs, matFileReader);
    }
    
    std::string LoadObj(std::vector<shape_t> &shapes,
                        std::vector<material_t> &materials, // [output]
                        std::istream &inStream, MaterialReader &readMatFn) {
        std::stringstream err;
        
        std::vector<float> v;
        std::vector<float> vn;
        std::vector<float> vt;
        std::vector<std::vector<vertex_index> > faceGroup;
        std::string name;
        
        // material
        std::map<std::string, int> material_map;
        std::map<vertex_index, unsigned int> vertexCache;
        int material = -1;
        
        shape_t shape;
        
        int maxchars = 8192;             // Alloc enough size.
        std::vector<char> buf(maxchars); // Alloc enough size.
        while (inStream.peek() != -1) {
            inStream.getline(&buf[0], maxchars);
            
            std::string linebuf(&buf[0]);
            
            // Trim newline '\r\n' or '\n'
            if (linebuf.size() > 0) {
                if (linebuf[linebuf.size() - 1] == '\n')
                    linebuf.erase(linebuf.size() - 1);
            }
            if (linebuf.size() > 0) {
                if (linebuf[linebuf.size() - 1] == '\r')
                    linebuf.erase(linebuf.size() - 1);
            }
            
            // Skip if empty line.
            if (linebuf.empty()) {
                continue;
            }
            
            // Skip leading space.
            const char *token = linebuf.c_str();
            token += strspn(token, " \t");
            
            assert(token);
            if (token[0] == '\0')
                continue; // empty line
            
            if (token[0] == '#')
                continue; // comment line
            
            // vertex
            if (token[0] == 'v' && isSpace((token[1]))) {
                token += 2;
                float x, y, z;
                parseFloat3(x, y, z, token);
                v.push_back(x);
                v.push_back(y);
                v.push_back(z);
                continue;
            }
            
            // normal
            if (token[0] == 'v' && token[1] == 'n' && isSpace((token[2]))) {
                token += 3;
                float x, y, z;
                parseFloat3(x, y, z, token);
                vn.push_back(x);
                vn.push_back(y);
                vn.push_back(z);
                continue;
            }
            
            // texcoord
            if (token[0] == 'v' && token[1] == 't' && isSpace((token[2]))) {
                token += 3;
                float x, y;
                parseFloat2(x, y, token);
                vt.push_back(x);
                vt.push_back(y);
                continue;
            }
            
            // face
            if (token[0] == 'f' && isSpace((token[1]))) {
                token += 2;
                token += strspn(token, " \t");
                
                std::vector<vertex_index> face;
                while (!isNewLine(token[0])) {
                    vertex_index vi =
                    parseTriple(token, static_cast<int>(v.size() / 3), static_cast<int>(vn.size() / 3), static_cast<int>(vt.size() / 2));
                    face.push_back(vi);
                    size_t n = strspn(token, " \t\r");
                    token += n;
                }
                
                faceGroup.push_back(face);
                
                continue;
            }
            
            // use mtl
            if ((0 == strncmp(token, "usemtl", 6)) && isSpace((token[6]))) {
                
                char namebuf[TINYOBJ_SSCANF_BUFFER_SIZE];
                token += 7;
#ifdef _MSC_VER
                sscanf_s(token, "%s", namebuf, _countof(namebuf));
#else
                sscanf(token, "%s", namebuf);
#endif
                
                // Create face group per material.
                bool ret = exportFaceGroupToShape(shape, vertexCache, v, vn, vt,
                                                  faceGroup, material, name, true);
                if (ret) {
                    shapes.push_back(shape);
                }
                shape = shape_t();
                faceGroup.clear();
                
                if (material_map.find(namebuf) != material_map.end()) {
                    material = material_map[namebuf];
                } else {
                    // { error!! material not found }
                    material = -1;
                }
                
                continue;
            }
            
            // load mtl
            if ((0 == strncmp(token, "mtllib", 6)) && isSpace((token[6]))) {
                char namebuf[TINYOBJ_SSCANF_BUFFER_SIZE];
                token += 7;
#ifdef _MSC_VER
                sscanf_s(token, "%s", namebuf, _countof(namebuf));
#else
                sscanf(token, "%s", namebuf);
#endif
                
                std::string err_mtl = readMatFn(namebuf, materials, material_map);
                if (!err_mtl.empty()) {
                    faceGroup.clear(); // for safety
                    return err_mtl;
                }
                
                continue;
            }
            
            // group name
            if (token[0] == 'g' && isSpace((token[1]))) {
                
                // flush previous face group.
                bool ret = exportFaceGroupToShape(shape, vertexCache, v, vn, vt,
                                                  faceGroup, material, name, true);
                if (ret) {
                    shapes.push_back(shape);
                }
                
                shape = shape_t();
                
                // material = -1;
                faceGroup.clear();
                
                std::vector<std::string> names;
                while (!isNewLine(token[0])) {
                    std::string str = parseString(token);
                    names.push_back(str);
                    token += strspn(token, " \t\r"); // skip tag
                }
                
                assert(names.size() > 0);
                
                // names[0] must be 'g', so skip the 0th element.
                if (names.size() > 1) {
                    name = names[1];
                } else {
                    name = "";
                }
                
                continue;
            }
            
            // object name
            if (token[0] == 'o' && isSpace((token[1]))) {
                
                // flush previous face group.
                bool ret = exportFaceGroupToShape(shape, vertexCache, v, vn, vt,
                                                  faceGroup, material, name, true);
                if (ret) {
                    shapes.push_back(shape);
                }
                
                // material = -1;
                faceGroup.clear();
                shape = shape_t();
                
                // @todo { multiple object name? }
                char namebuf[TINYOBJ_SSCANF_BUFFER_SIZE];
                token += 2;
#ifdef _MSC_VER
                sscanf_s(token, "%s", namebuf, _countof(namebuf));
#else
                sscanf(token, "%s", namebuf);
#endif
                name = std::string(namebuf);
                
                continue;
            }
            
            // Ignore unknown command.
        }
        
        bool ret = exportFaceGroupToShape(shape, vertexCache, v, vn, vt, faceGroup,
                                          material, name, true);
        if (ret) {
            shapes.push_back(shape);
        }
        faceGroup.clear(); // for safety
        
        return err.str();
    }
}