A few designs are predicted to be less efficient when fabricated by 3D printing versus bulk casting, namely the vertically printed parts (12, 17, 18) and the cylinder array (21). This reduced efficiency could be partially explained by the directionality arguments made above: verticallyprinted parts would direct more light towards the top and bottom surfaces rather than the edges, thereby leading to a decrease in the number of photons counted in the edge output. Similarly, for the cylinder array re-emitted rays would be more likely to be emitted perpendicular to the edges and therefore enter another cylinder and potentially be reabsorbed by the luminophore or parasitically-absorbed by the waveguide. Furthermore, for vertically-printed parts, we see a larger reduction in efficiency in the surface normal calculation than the enclosing box calculation. This could be due to the curved surfaces introduced by the 3D printing process, meaning fewer edge faces would satisfy the criteria of being counted by the surface normal method, while the enclosing box method is agnostic to the edge emission surface. .