Question

I need help loading a custom file format into my program made in c++…
I know there’s a simple way of doing this but I think I’m using the
wrong terms to search for it online…

My custom format for 3d objects is as follows:

NumVerts 6
//verts (float)
-1
-1
0
1
-1
0
-1
1
0
1
-1
0
1
1
0
-1
1
0
//texture (float)
0
0
1
0
0
1
1
0
1
1
0
1
//index (int)
0
1
2
1
3
2

And that is a quad… (yeas; I know… horrible format… but it’s what I’m using for an android game).

I want to make a function in c++ for my editor (SDL + OpenGL for windows) that loads these files into data… Unfortunately though I know how to export this format with C++, I can’t figure out how to import them… I wish to use the fstream commands…

If someone could quickly write out a simple version I’d be really thankful.

I just it to do the following:

• Find text file from input string
• read “NumVerts” and grab the integer written after it
• loop through the next (NumVerts*3) lines and grab each number as a float
• loop though the next (NumVerts*2) lines and grab each number as a float
• loop through the next (NumVerts*1) lines and grab each number as an Int
• (skip any line that starts with “//”)
• close file.

Thank you for reading and any help would be really good right now… or a relivent link that is quite simple and reads strings from files and grabs numbers from them to be placed into memory…

I really just want to finish this game and it’s getting really stressful trying to locate helpful tutorials.

Update: updated the script… I accidently forgot to seperate 1’s and 0’s…

Answer 1

Hope this helps. Incidentally, you have the wrong number of vertex components – you need 18 of them.

#include <algorithm>
#include <exception>
#include <fstream>
#include <iostream>
#include <string>
#include <vector>

#include <boost/algorithm/string/trim.hpp>
#include <boost/lexical_cast.hpp>
using boost::lexical_cast;

int load_3d_object(const std::string& filename,
                   std::vector<float>& vertComponents,
                   std::vector<float>& texComponents,
                   std::vector<int>& indices)
{
    std::ifstream fs(filename.c_str());
    std::string line;
    if(!std::getline(fs, line))
    {
        throw std::runtime_error("The input file is empty");
    }

    if(line.substr(0,8) != "NumVerts")
    {
        throw std::runtime_error("The first line must start with NumVerts");
    }

    // Extract the number of vertices.
    int numVerts = lexical_cast<int>(line.substr(line.find(' ') + 1));

    // Read in the vertex components, texture components and indices.
    while(std::getline(fs, line))
    {
        boost::trim(line);
        if(line.substr(0,2) == "//") continue;

        if((int)vertComponents.size() < numVerts * 3)       vertComponents.push_back(lexical_cast<float>(line));
        else if((int)texComponents.size() < numVerts * 2)   texComponents.push_back(lexical_cast<float>(line));
        else                                                indices.push_back(lexical_cast<int>(line));
    }

    return numVerts;
}

int main()
{
    std::vector<float> vertComponents;
    std::vector<float> texComponents;
    std::vector<int> indices;
    try
    {
        int numVerts = load_3d_object("input.txt", vertComponents, texComponents, indices);
    }
    catch(std::exception& e)
    {
        std::cout << e.what() << '\n';
    }
    return 0;
}