Calculates lines that are tangential to both the first and the second curve. Returns an array of 2D points, where each pair of points represent a line. The number of points is always even. Implemented for circles or arcs only.

Calculates the start- and endpoints of lines that are tangential to the given curves. There may be any number of solutions, including no solution. Each solution consists of two points: 1.: the startpoint, 2.: the endpoint of the Line. the startpoint lies on the first curve, the endpoint on the second. The length of the returned array is a multiple of 2 (or 0). If both curves are circles or arcs, all possible solutions are returned. If a curve is mor complex than a circle (e.g. bspline, ellipse) only the solution closest to the points p1 and p2 is returned.