private void AddCube(float cube_half_size, Point3d point, Color color, float specular = 0, float reflecive = 0, float transparent = 0)
{
var cube = new Polyhedron();
cube.MakeHexahedron(cube_half_size);
cube.Translate(point.X, point.Y, point.Z);
cube.color = color;
cube.specular = specular;
cube.reflective = reflecive;
cube.transparent = transparent;
cube.FindNormals();
polyhedrons.Add(cube);
}