C ++ OBJ文件解析器

Question

I am making a file parser for the OBJ files and everything is going into the correct place but for some reason it doesn't run till the end of the file.

    void loader::readIn()
{
    //!takes in the all the data and 
    //!puts in string first.
    std::string line;

    while(!myFile.eof())
    {

        linetype = unknown;//enum set to uknown
        line.clear(); // clear line
        ss.clear();  // clear string stream
        std::getline(myFile,line); //intake line , to string line

        //found = line.find("v "); //enum to check the line type i,e Face ,vertex
        if(line[0] == 'v') //! check to see if the first char is v
           {
             linetype = vertex;   

           }

    //  found = line.find("f ");
        if(line[0] == 'f') //! checkl to see if the first char is f
        {
            linetype = face;

        }

    //  found = line.find("vn ");
        if(line[0] == 'vn') //! checkl to see if the first char is vn 
        {

            linetype = vertexNormal;

        }
        //  found = line.find("vt ")
        if(line[0] == 'vt') //! checkl to see if the first char is vt
        {
            linetype = vertexTexture;

        }

            if(line[0] == ' ' || '#') // if the start of the line is empty or a #
        {
            line.clear();   //clear line
                std::getline(myFile,line); // intake the next line
        }



        switch(linetype)
        { 
        case vertex:     //!stores the verrtex floats in vert.

            ss >> vertexFloat[0] >> vertexFloat[1] >> vertexFloat[2];
            verts.push_back(new coordinate(vertexFloat[0],vertexFloat[1],vertexFloat[2])); //creates new coord
            linetype = unknown;
            break;

        case face:
            int n; // these are the counters for the float arrays
            int m;
            int b;
            n = 0;
            m = 0;
            b = 0;
            int faces[3];   //temperary float array
            int faceText[3];
            int faceNorm[3];
            ss.str(line);  //string stream  intake line
            ss.ignore(1); 
            while( !ss.eof())
            {

                ss >> faces[n]; // intake first umber
                n++;

                 if(ss.peek() == '/')
                 {
                     ss.ignore(1);

                     if(ss.peek() != '/')
                    { 
                      ss >> faceText[m];
                      m++;
                     }
                 }

                ss.ignore(1);
                ss >> faceNorm[b];
                b++;

             }


            for( int i = 0; i < 3 ; ++i)
            {
            totalFaces.push_back(faces[i]);  // push back all the ints on the correct
            faceTexture.push_back(faceText[i]); // vector
            faceNormal.push_back(faceNorm[i]);
            }
            break;

This is the code it takes in the first 3 lines then just stops. I am checking the totalFaces vector which takes in the first number of each set of 3.

**f 1/2/3 4//6 7/8/9
f 1/2/3 4//6 7/8/9
f 1/2/3 4//6 7/8/9
f 1/2/3 4//6 7/8/9
f 1/2/3 4//6 7/8/9
f 1/2/3 4//6 7/8/9
f 1/2/3 4//6 7/8/9
f 1/2/3 4//6 7/8/9
f 1/2/3 4//6 7/8/9**

is my obj file.

Answer 1

You don't have to use eof(). Look my code:

void Mesh::LoadObjModel(const char *filename)
{
  std::ifstream in(filename, std::ios::in);
  if (!in)
    {
        std::cerr << "Cannot open " << filename << std::endl;
        exit(1);

    }
  std::string line;
  while (std::getline(in, line))
  {
    //check v for vertices
     if (line.substr(0,2)=="v "){
        std::istringstream v(line.substr(2));
        glm::vec3 vert;
        double x,y,z;
        v>>x;v>>y;v>>z;
        vert=glm::vec3(x,y,z);
        vertices.push_back(vert);
  }
  //check for texture co-ordinate
  else if(line.substr(0,2)=="vt"){

      std::istringstream v(line.substr(3));
      glm::vec2 tex;
      int U,V;
      v>>U;v>>V;
      tex=glm::vec2(U,V);
      texture.push_back(tex);

  }
  //check for faces
  else if(line.substr(0,2)=="f "){
    int a,b,c; //to store mesh index
    int A,B,C; //to store texture index
    //std::istringstream v;
  //v.str(line.substr(2));
  const char* chh=line.c_str();
    sscanf (chh, "f %i/%i %i/%i %i/%i",&a,&A,&b,&B,&c,&C); //here it read the line start with f and store the corresponding values in the variables

    //v>>a;v>>b;v>>c;
    a--;b--;c--;
    A--;B--;C--;
    //std::cout<<a<<b<<c<<A<<B<<C;
    faceIndex.push_back(a);textureIndex.push_back(A);
    faceIndex.push_back(b);textureIndex.push_back(B);
    faceIndex.push_back(c);textureIndex.push_back(C);
  }

}
//the mesh data is finally calculated here
for(unsigned int i=0;i<faceIndex.size();i++)
{
    glm::vec3 meshData;
    glm::vec2 texData;
    meshData=glm::vec3(vertices[faceIndex[i]].x,vertices[faceIndex[i]].y,vertices[faceIndex[i]].z);
    texData=glm::vec2(texture[textureIndex[i]].x,texture[textureIndex[i]].y);
    meshVertices.push_back(meshData);
    texCoord.push_back(texData);
}

}

In above sample code the 'Vn' for normal is missing. You can add another condition to check 'Vn' similar to other. I hope this could solve you problem. If you need complete sample program then look here .

Answer 2

It's incorrect to check eof() in the loop condition. It's not a prediction, it indicates that the previous read failed because of EOF. Eg even an empty file doesn't start with .eof true.

Also, 'vn' is neither one character nor two characters. line[0] definitely is one character and obviously cannot equal the two characters "vn".