objpar

Single header Wavefront OBJ parser.

Currently it depends on stdlib's atoi and atof. You can provide your own implementation by doing

#define objpar_atoi my_atoi

#define objpar_atof my_atof

For now it only supports:

• Geometric Vertices.
• Vertex Normals.
• Texture Vertices
• Faces

The current implementation defines two structures. The first one is struct objpar_data and the second one is struct objpar_mesh.

The only function call needed to parse the OBJ string is objpar.

This is the signature of the function:

unsigned int objpar(
    const char* p_string,               /* Raw string */
    unsigned int string_size,           /* String size */
    void* p_buffer,                     /* User allocated buffer with the size provided by objpar_get_size() */
    struct objpar_data* p_data          /* Structure used to store the OBJ parsed data */
);

/* Usage */

struct objpar_data obj_data;

p_data = open_file("my_file.obj", &file_size);

p_buffer = malloc(objpar_get_size(p_data, file_size));

objpar(p_data, file_size, p_buffer, &obj_data);

The function objpar_build_mesh will generate a flat array containing the vertex data for the specified struct objpar_data structure.

The vertex structure will depend on which parameters are stored on the parsed obj file. Here is how it would look for a file with position, normals and texture coordinates.

struct vertex
{
    float position[POSITION_WIDTH];
    float texcoord[TEXCOORD_WIDTH];
    float normals[NORMALS_WIDTH];
};

The struct objpar_mesh structure will provide the data, vertex stride, vertex count, position, texcoord and normal offsets. With this information you can define your vertex input layout for different graphics API. If an offset has a value of -1 it means that it's not part of the vertex.

The signature for the function objpar_build_mesh is:

unsigned int objpar_build_mesh(
    const struct objpar_data* p_data,       /* Data obtained by objpar function */
    void* p_buffer,                         /* User allocated buffer with the size provided by objpar_get_mesh_size() */
    struct objpar_mesh* p_mesh              /* Structure used to store the mesh data */ 
);

/* Usage */

void* p_mesh_buffer = malloc(objpar_get_mesh_size(&obj_data));

objpar_build_mesh(&obj_data, p_mesh_buffer, &obj_mesh);

Repo: https://github.com/bitnenfer/objpar/

Wavefront OBJ Format Specification: http://www.martinreddy.net/gfx/3d/OBJ.spec

  Copyright © 2000 Felipe Alfonso <felipe@voidptr.io>
  This work is free. You can redistribute it and/or modify it under the
  terms of the Do What The Fuck You Want To Public License, Version 2,
  as published by Sam Hocevar. See http://www.wtfpl.net/ for more details.