If the annulus is acceptable as a 2-D solution (mentioned earlier in this discussion), then your annular torus would have to be acceptable in 3-D too. I don't think either should count. It has to be actually physically viable for fertilizer purposes. On 5/9/12, Warren Smith <warren.wds@gmail.com> wrote:
Actually, a nice 3D solution occurs to me... which unfortunately seems useless and is kind of a cheat.
Make a torus, i.e. the points within distance <=1 from a large circle. Also, make that circle itself be a "surface" (of area=0, or you could make it be another torus so the area was positive).
The torus erodes from both the outside-in and the inside-out and always has constant surface until the instant it vanishes.
Cute... except not useful for fertilizer purposes since only the surfaces ACCESSIBLE from the outside are allowed to erode in real life. [...]
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