In the end, I will likely either paint it UFB or line it with appropriate material. I'm not worried about it losing fur. :) But it's an interesting challenge between the computational aspects and the need to 3D print the result. I only have one other complaint about this sensor, that it's TOO SENSITIVE! I've seen it trigger during daytime on lightning 60 miles away. The cube approach is interesting, those would make corner reflectors, but I don't care where else the light bounces, just not into my sensor. The inside surfaces of the pyramid are diffuse reflectors, so even out at +/- 90 degrees almost, some light will hit the inner surface of the pyramid, and some of that will end up in the sensor. If I could make the inner surfaces specular (and FLAT!) then I would actually have a simpler problem in that I could know where the light rays will and won't go. "First, assume the cow is a perfect sphere..." :) -- K1FZY (WA4TPW) SK 9/29/37-4/13/15