The union of congruent cubes in three dimensions

  • Authors:
  • J. Pach;Ido Safruti;Micha Sharir

  • Affiliations:
  • Department of Computer Science, City College, CUNY, New York, NY and Courant Institute of Mathematical Sciences, New York University, New York, NY and Hungarian, Academy of Sciences, Budapest, Hun ...;School of Mathematical Sciences, Tel Aviv University, Tel Aviv, 69978, Israel;School of Mathematical Sciences, Tel Aviv University, Tel Aviv 69978, Israel, and Courant Institute of Mathematical, Sciences, New York University, New York, NY

  • Venue:
  • SCG '01 Proceedings of the seventeenth annual symposium on Computational geometry
  • Year:
  • 2001

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Abstract

A {\em dihedral (trihedral) wedge} is the intersection of two (resp. t hree) half-spaces in $\reals^3$. It is called {\em $\alpha$-fat} if the angle (resp., solid angle) determined by these half-spaces is at least $\alpha0$. If, in addition, the sum of the three face angles of a trihedral wedge is at least $\gamma 4\pi/3$, then it is called {\em $(\gamma,\alpha)$-substantially fat}. We prove that, for any fixed $\gamma4\pi/3, \alpha0$, the combinatorial complexity of the union of $n$ (a) $\alpha$-fat dihedral wedges, (b) $(\gamma,\alpha)$-substantially fat trihedral wedges is at most $O(n^{2+\eps})$, for any $\eps0$, where the constants of proportionality depend on $\eps$, $\alpha$ (and $\gamma$).We obtain as a corollary that the same upper bound holds for the combinatorial complexity of the union of $n$ (nearly) congruent cubes in $\reals^3$. These bounds are not far from being optimal.