i'd say that's because culling is not enabled so it's lighting both the back and front faces. you can call:
glEnable(GL_CULL_FACE);
glCullFace(GL_FRONT);there's a problem with some primitives in OF where the culling is reversed because of the way we create the mesh, we'll fix it in the next release but by now, if that doesn't work try with glCullFace(GL_BACK)
