Why isn't my lighting working properly? Are my normals messed up?
- by Radek Slupik
I'm relatively new to OpenGL and I am trying to draw a 3D model (loaded from a 3ds file using lib3ds) using OpenGL with lighting, but about half of it is drawn in black.
I set up the light as such:
glEnable(GL_LIGHTING);
glShadeModel(GL_SMOOTH);
GLfloat ambientColor[] = {0.2f, 0.2f, 0.2f, 1.0f};
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientColor);
glEnable(GL_LIGHT0);
GLfloat lightColor0[] = {1.0f, 1.0f, 1.0f, 1.0f};
GLfloat lightPos0[] = {4.0f, 0.0f, 8.0f, 0.0f};
glLightfv(GL_LIGHT0, GL_DIFFUSE, lightColor0);
glLightfv(GL_LIGHT0, GL_POSITION, lightPos0);
The model is in a VBO and drawn using glDrawArrays. The normals are in a separate VBO, and the normals are calculated using lib3ds_mesh_calculate_vertex_normals:
std::vector<std::array<float, 3>> normals;
for (std::size_t i = 0; i < model->nmeshes; ++i) {
auto& mesh = *model->meshes[i];
std::vector<float[3]> vertex_normals(mesh.nfaces * 3);
lib3ds_mesh_calculate_vertex_normals(&mesh, vertex_normals.data());
for (std::size_t j = 0; j < mesh.nfaces; ++j) {
auto& face = mesh.faces[j];
normals.push_back(make_array(vertex_normals[j]));
}
}
glBindBuffer(GL_ARRAY_BUFFER, normal_vbo_);
glBufferData(GL_ARRAY_BUFFER,
normals.size() * sizeof(decltype(normals)::value_type),
normals.data(),
GL_STATIC_DRAW);
The problem isn't the vertices; the model is drawn correctly when drawing it as a wireframe. I also fixed the normals in Blender using controlN. What could be the problem? Should I store the normals in a different order?
