This design was inspired by a larger bronze cast sculpture I made in Spring 2007 which can be seen on my university website www.math.binghamton.edu/alex/sculptures_spr07.html Each of the two upwardly spiraling surfaces has a hypocycloid cross section (concave triangle), and they meet at the top so that the piece is strong enough to withstand the polishing process after 3D printing. Many variations of this design are possible, including those with more twisting as the curves ascend, and a steeper ascent with fewer turns to the top. It was not intended to look like a Christmas tree, but has that look, and would hang nicely from a thin nylon wire, twisting in the wind. Other designers on Shapeways have used such a spiraling design tapering at both top and bottom, but perhaps not with the same triangular cross section. This would look cool on your desk top.