tiny_obj_loader example

    // Load mesh
    std::vector<vertex_t> objModel;
    bool hasNormals = false;
    {
        // A constant scale to apply to all vertex positions
        float scale = 0.5f;

        std::string warn;
        std::string err;
        tinyobj::attrib_t attrib;
        std::vector<tinyobj::shape_t> shapes;

        tinyobj::LoadObj(&attrib, &shapes, NULL, &warn, &err, "media/teapot.obj", NULL, true);
        if (!err.empty())
            printf("Error loading obj: %s\n", err.c_str());
        if (!warn.empty())
            printf("Warning loading obj: %s\n", warn.c_str());

        hasNormals = !attrib.normals.empty();

        for (const tinyobj::shape_t& shape : shapes)
        {
            for (const tinyobj::index_t& index : shape.mesh.indices)
            {
                vertex_t v;
                v.position = {
                    scale * attrib.vertices[index.vertex_index * 3 + 0],
                    scale * attrib.vertices[index.vertex_index * 3 + 1],
                    scale * attrib.vertices[index.vertex_index * 3 + 2]
                };

                if (hasNormals)
                {
                    v.normal = {
                        attrib.normals[index.normal_index * 3 + 0],
                        attrib.normals[index.normal_index * 3 + 1],
                        attrib.normals[index.normal_index * 3 + 2]
                    };
                }

                objModel.push_back(v);
            }
        }
    }

    if (!hasNormals)
    {
        for (int i = 0; i < objModel.size(); i += 3)
        {
            vertex_t& v0 = objModel[i+0];
            vertex_t& v1 = objModel[i+1];
            vertex_t& v2 = objModel[i+2];

            vec3_t normal = vec3_cross((v1.position - v0.position), (v2.position - v0.position));
            v0.normal = v1.normal = v2.normal = normal;
        }
    }