tinyobjloader/examples/callback_api/main.cc

//
// An example of how to use callback API.
// This example is minimum and incomplete. Just showing the usage of callback
// API.
// You need to implement your own Mesh data struct constrution based on this
// example in practical.
//
#define TINYOBJLOADER_IMPLEMENTATION
#include "tiny_obj_loader.h"

#include <cassert>
#include <cstdio>
#include <cstdlib>
#include <fstream>
#include <iostream>
#include <sstream>

typedef struct {
  std::vector<float> vertices;
  std::vector<float> normals;
  std::vector<float> texcoords;
  std::vector<int> v_indices;
  std::vector<int> vn_indices;
  std::vector<int> vt_indices;

  std::vector<tinyobj::material_t> materials;

} MyMesh;

void vertex_cb(void *user_data, float x, float y, float z, float w) {
  MyMesh *mesh = reinterpret_cast<MyMesh *>(user_data);
  printf("v[%ld] = %f, %f, %f (w %f)\n", mesh->vertices.size() / 3, x, y, z, w);

  mesh->vertices.push_back(x);
  mesh->vertices.push_back(y);
  mesh->vertices.push_back(z);
  // Discard w
}

void normal_cb(void *user_data, float x, float y, float z) {
  MyMesh *mesh = reinterpret_cast<MyMesh *>(user_data);
  printf("vn[%ld] = %f, %f, %f\n", mesh->normals.size() / 3, x, y, z);

  mesh->normals.push_back(x);
  mesh->normals.push_back(y);
  mesh->normals.push_back(z);
}

void texcoord_cb(void *user_data, float x, float y, float z) {
  MyMesh *mesh = reinterpret_cast<MyMesh *>(user_data);
  printf("vt[%ld] = %f, %f, %f\n", mesh->texcoords.size() / 3, x, y, z);

  mesh->texcoords.push_back(x);
  mesh->texcoords.push_back(y);
  mesh->texcoords.push_back(z);
}

void index_cb(void *user_data, tinyobj::index_t *indices, int num_indices) {
  // NOTE: the value of each index is raw value.
  // For example, the application must manually adjust the index with offset
  // (e.g. v_indices.size()) when the value is negative(whic means relative
  // index).
  // Also, the first index starts with 1, not 0.
  // See fixIndex() function in tiny_obj_loader.h for details.
  // Also, 0 is set for the index value which
  // does not exist in .obj
  MyMesh *mesh = reinterpret_cast<MyMesh *>(user_data);

  for (int i = 0; i < num_indices; i++) {
    tinyobj::index_t idx = indices[i];
    printf("idx[%ld] = %d, %d, %d\n", mesh->v_indices.size(), idx.vertex_index,
           idx.normal_index, idx.texcoord_index);

    if (idx.vertex_index != 0) {
      mesh->v_indices.push_back(idx.vertex_index);
    }
    if (idx.normal_index != 0) {
      mesh->vn_indices.push_back(idx.normal_index);
    }
    if (idx.texcoord_index != 0) {
      mesh->vt_indices.push_back(idx.texcoord_index);
    }
  }
}

void usemtl_cb(void *user_data, const char *name, int material_idx) {
  MyMesh *mesh = reinterpret_cast<MyMesh *>(user_data);
  if ((material_idx > -1) && (material_idx < mesh->materials.size())) {
    printf("usemtl. material id = %d(name = %s)\n", material_idx,
           mesh->materials[material_idx].name.c_str());
  } else {
    printf("usemtl. name = %s\n", name);
  }
}

void mtllib_cb(void *user_data, const tinyobj::material_t *materials,
               int num_materials) {
  MyMesh *mesh = reinterpret_cast<MyMesh *>(user_data);
  printf("mtllib. # of materials = %d\n", num_materials);

  for (int i = 0; i < num_materials; i++) {
    mesh->materials.push_back(materials[i]);
  }
}

void group_cb(void *user_data, const char **names, int num_names) {
  // MyMesh *mesh = reinterpret_cast<MyMesh*>(user_data);
  printf("group : name = \n");

  for (int i = 0; i < num_names; i++) {
    printf("  %s\n", names[i]);
  }
}

void object_cb(void *user_data, const char *name) {
  // MyMesh *mesh = reinterpret_cast<MyMesh*>(user_data);
  printf("object : name = %s\n", name);
}

int main(int argc, char **argv) {
  tinyobj::callback_t cb;
  cb.vertex_cb = vertex_cb;
  cb.normal_cb = normal_cb;
  cb.texcoord_cb = texcoord_cb;
  cb.index_cb = index_cb;
  cb.usemtl_cb = usemtl_cb;
  cb.mtllib_cb = mtllib_cb;
  cb.group_cb = group_cb;
  cb.object_cb = object_cb;

  MyMesh mesh;
  std::string warn;
  std::string err;
  std::string filename = "../../models/cornell_box.obj";
  if (argc > 1) {
    filename = std::string(argv[1]);
  }
  std::ifstream ifs(filename.c_str());

  if (ifs.fail()) {
    std::cerr << "file not found." << std::endl;
    return EXIT_FAILURE;
  }

  tinyobj::MaterialFileReader mtlReader("../../models/");

  bool ret = tinyobj::LoadObjWithCallback(ifs, cb, &mesh, &mtlReader, &warn, &err);

  if (!warn.empty()) {
    std::cout << "WARN: " << warn << std::endl;
  }

  if (!err.empty()) {
    std::cerr << err << std::endl;
  }

  if (!ret) {
    std::cerr << "Failed to parse .obj" << std::endl;
    return EXIT_FAILURE;
  }

  printf("# of vertices         = %ld\n", mesh.vertices.size() / 3);
  printf("# of normals          = %ld\n", mesh.normals.size() / 3);
  printf("# of texcoords        = %ld\n", mesh.texcoords.size() / 2);
  printf("# of vertex indices   = %ld\n", mesh.v_indices.size());
  printf("# of normal indices   = %ld\n", mesh.vn_indices.size());
  printf("# of texcoord indices   = %ld\n", mesh.vt_indices.size());
  printf("# of materials = %ld\n", mesh.materials.size());

  return EXIT_SUCCESS;
}