generates vmd script (tcl) that draw polygon on vmd from STL binary format file.

stl_to_vmd.cpp

/* Description: this program generates vmd script file (.tcl file) that draws    *
 *              polygon structure on vmd from STL binary-format file.            *
 *                                                                               *
 * Licensing Terms : This code is licensed under the MIT License.                *
 * copyright (c) 2016 Toru Niina (niina.toru.68u@gmail.com)                      *
 * all rights reserved.                                                     　   *
 *                                                                               *
 * Permission is hereby granted, free of charge, to any person obtaining a copy  *
 * of this software and associated documentation files (the "Software"), to deal *
 * in the Software without restriction, including without limitation the rights  *
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell     *
 * copies of the Software, and to permit persons to whom the Software is         *
 * furnished to do so, subject to the following conditions:                      *
 *                                                                               *
 * The above copyright notice and this permission notice shall be included in    *
 * all copies or substantial portions of the Software.                           *
 *                                                                               *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR    *
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,      *
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE   *
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER        *
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, *
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN     *
 * THE SOFTWARE.                                                                 *
 *                                                                               */

#include <iostream>
#include <fstream>
#include <string>
#include <stdexcept>

constexpr static std::size_t sizeof_uint  = sizeof(unsigned int);
constexpr static std::size_t sizeof_float = sizeof(float);

struct position
{
    float x, y, z;
};

struct triangle
{
    position a, b, c;
};

std::ostream& operator<<(std::ostream& os, const position& pos)
{
    os << pos.x << " " << pos.y << " " << pos.z;
    return os;
}

std::ostream& operator<<(std::ostream& os, const triangle& tri)
{
    os << "draw triangle {" << tri.a << "} {"
                            << tri.b << "} {" << tri.c << "}" << std::endl;
    return os;
}

position read_vector(std::ifstream& ifs)
{
    char *float0 = new char [sizeof_float];
    char *float1 = new char [sizeof_float];
    char *float2 = new char [sizeof_float];

    ifs.read(float0, sizeof_float);
    ifs.read(float1, sizeof_float);
    ifs.read(float2, sizeof_float);

    const float x = *reinterpret_cast<float*>(float0);
    const float y = *reinterpret_cast<float*>(float1);
    const float z = *reinterpret_cast<float*>(float2);

    delete [] float0;
    delete [] float1;
    delete [] float2;

    return position{x, y, z};
}

void read_triangle(std::ifstream& ifs)
{
    const position normal = read_vector(ifs);
    std::cout << "# normal " << normal << std::endl;
    const position A = read_vector(ifs);
    const position B = read_vector(ifs);
    const position C = read_vector(ifs);

    triangle tri = {A, B, C};
    std::cout << tri << std::endl;

    char *unused_data = new char [2];
    ifs.read(unused_data, 2);
    delete [] unused_data;

    return;
}

int main(int argc, char **argv)
{
    try
    {
    if(argc != 2)
    {
        std::cerr << "usage: ./stl2vmd [filename].stl (binary only) > vmd.tcl" << std::endl;
        return 1;
    }
    const std::string filename = argv[1];
    std::ifstream stlfile(filename, std::ios::in | std::ios::binary);
    if(!stlfile.good())
        throw std::runtime_error("file open error");

    std::cerr << "file reading start." << std::endl;
    std::cout << "draw delete all" << std::endl;

    stlfile.seekg(0, stlfile.end);
    const std::size_t size_of_file = stlfile.tellg();
    stlfile.seekg(0, stlfile.beg);

    std::cerr << "file size: " << size_of_file << std::endl;

    char *ch_header = new char[81];
    stlfile.read(ch_header, 80);
    ch_header[80] = '\0';
    const std::string header(ch_header);
    delete [] ch_header;

    std::cerr << "header   : " << header << std::endl;

    char *ch_numTriangle = new char [sizeof_uint];
    stlfile.read(ch_numTriangle, sizeof_uint);
    const std::size_t num_Triangle = *reinterpret_cast<unsigned int*>(ch_numTriangle);
    delete [] ch_numTriangle;
    std::cerr << "# of face: " << num_Triangle << std::endl;

    if(50 * num_Triangle + 80 + sizeof_uint != size_of_file)
    {
        std::cerr << "file size must be 50 * number of triangle + 80 + 4" << std::endl;
        std::cerr << " = " << 50 * num_Triangle + 80 + sizeof_uint << std::endl;
        throw std::runtime_error("invalid filesize");
    }

    for(std::size_t i=0; i < num_Triangle; ++i)
    {
        read_triangle(stlfile);
    }

    return 0;
    }
    catch(std::exception& except)
    {
    std::cerr << "exception thrown. what: " << except.what() << std::endl;
    return 1;
    }
}