Prismatoid Band-Unfolding Revisited
This addresses a specific case in computational geometry related to Dürer's problem, but it is incremental as it does not solve the broader unsolved problem.
The paper tackles the problem of determining when a band-unfolding of a nested prismatoid results in a nonoverlapping unfolding, showing that a known counterexample is essentially the only possible one, though it does not expand the class of shapes with known edge-unfoldings.
It remains unknown if every prismatoid has a nonoverlapping edge-unfolding, a special case of the long-unsolved "Dürer's problem." Recently nested prismatoids have been settled [Rad24] by mixing (in some sense) the two natural unfoldings, petal-unfolding and band-unfolding. Band-unfolding fails due to a specific counterexample [O'R13b]. The main contribution of this paper is a characterization when a band-unfolding of a nested prismatoid does in fact result in a nonoverlapping unfolding. In particular, we show that the mentioned counterexample is in a sense the only possible counterexample. Although this result does not expand the class of shapes known to have an edge-unfolding, its proof expands our understanding in several ways, developing tools that may help resolve the non-nested case.