10.3 Point/point"intersection Check if R1-R2 e, where e represents the maximum allowable tolerance Choice of"tolerances"in a geometric modeller is difficult-an open question Lack of transitivity, see Figure 10.4 R1=R2→R1≠R3 R=Rs R R Figure 10.4: Intersections of points within a tolerance is intransitive ● What should e reflect?10.3 Point/point “intersection” • Check if |R1 − R2| < , where  represents the maximum allowable tolerance. • Choice of “tolerances” in a geometric modeller is difficult–an open question. • Lack of transitivity, see Figure 10.4: R1 = R2 R2 = R3 ⇒ R1 6= R3 R2 R3   . . . R1 Figure 10.4: Intersections of points within a tolerance is intransitive. • What should  reflect? 7