No abstract

We prove uniqueness results for conies of minimal area that enclose a compact, fulldimensional subset of the elliptic plane. The minimal enclosing conic is unique if its center or axes are prescribed. Moreover, we provide sufficient conditions on the enclosed set that guarantee uniqueness without restrictions on the enclosing conies. Similar results are formulated for minimal enclosing conies of line sets as well.

We present a method for guaranteed collision detection with toleranced motions. The basic idea is to consider the motion as a curve in the 12-dimensional space of affine displacements, endowed with an object-oriented Euclidean metric, and cover it with balls. The associated orbits of points, lines, planes and polygons have particularly simple shapes that lend themselves well to exact and fast collision queries. We present formulas for elementary collision tests with these orbit shapes and we suggest an algorithm, based on motion subdivision and computation of bounding balls, that can give a no-collision guarantee. It allows a robust and efficient implementation and parallelization. At hand of several examples we explore the asymptotic behavior of the algorithm and compare different implementation strategies.

No abstract

We present uniqueness results for enclosing ellipses of minimal area in the hyperbolic plane. Uniqueness can be guaranteed if the minimizers are sought among all ellipses with prescribed axes or center. In the general case, we present a sufficient and easily verifiable criterion on the enclosed set that ensures uniqueness.