private Color getDiffuseColor(Vector3D pt, Light light, Vector3D normal,
			Material material) {
		Color diffuse = null;
		if (light.getType() == Light.SPOT_LIGHT_ALL_DIRECTION) {
			Vector3D toLightDirection = Vector3D.Substract(light.getPos(), pt);
			double cos = Vector3D.cos(toLightDirection, normal);

			if (cos > 0) {
				diffuse = Color.DotMultiply(light.getDiffuse(),
						material.getDiffuse());
				diffuse.Scale(cos);
				System.out.println("cos = " + cos);
			}
		}
		return diffuse;
	}