Simultaneous Ellipse Scan Conversion

Question

Problem: Given two points (lying on an ellipse) (x1,y1) and (x2,y2) in the first quadrant. Scan convert the ellipse/elliptical arc from both ends simultaneously/point plotting should begin from both the ends at the same time.

My solution so far: I can scan convert the ellipse from (x1,y1) to (x2,y2) or vice versa easily using Mid-Point Scan Conversion algorithm. However, when it needs to be done simultaneously, I have no idea. The sources I've referred to show there is only quadrant symmetry in an ellipse, so I'm unable to think on how to simultaneously plot it.

Answer 1

If your threads are allowed to communicate while they progress, let them do the work from their respective endpoint and stop when they meet.

If they can't communicate, decide the meeting point in advance in a balanced way, ie by predicting where half the number of steps will lead you.