After playing with the magnitude of a diamond pattern as LED diffuser for Glow Flow, it looked like the easiest thing to do for a good blend is put more distance between the LEDs and their diffuser. Which led to the next question: where should that distance be? Because these diffusers were printed in vase mode, they actually have two surfaces to help with diffusion: an inner layer and an outer layer. It looks like the outer layer needs to be about 2cm away from the LEDs, but where should the inner layer be?
If we put the inner layer close to the LEDs, it would get first stab at diffusing light early, hopefully increasing its impact on outer layer diffusion. If we put the inner layer further away, it would receive a more diffuse input to begin with. Which would end up looking better?
To test which of the two might be better, a quick test was printed up with two different separation distances between inner and outer layers. Putting them up against Glow Flow LED core, the winner was… neither. It was basically a tie.
When we held the outer layer at the same distance from LEDs, visual output is nearly indistinguishable up close. From further away, they were identical. It appears for this 3D printed diffuser approach, the position of inner layer does not matter. It is the position of outer layer that will determine diffusion.
Based on these experiments with 3D printed diffusers, neither a surface texture nor texture magnitude nor layer separation made a significant improvement in appearance. The variable with most impact is distance of outer surface from LEDs.
In commercial product development, devoting such distance for diffusers is problematic because that is empty space not productive for whatever the product is supposed to do. One example: LED taillights in cars have a very limited space budget, because any volume consumed for good diffusion means less trunk space.
But for a hobbyist project like Glow Flow, where the whole point is appearance, we can freely devote volume to allow LED diffusion with a simple 3D printed mechanism. The next step is to think about how this diffuser will be installed.