redef var vertices is lazy do
		var a = [-0.5, 0.0, -0.5]
		var b = [ 0.5, 0.0, -0.5]
		var c = [-0.5, 0.0,  0.5]
		var d = [ 0.5, 0.0,  0.5]

		var vertices = new Array[Float]
		for v in [c, d, a, b] do vertices.add_all v
		return vertices
	end