Points of Graphic Oval

Quentin Long cubist at aol.com
Mon Jul 31 21:46:18 CEST 2017


The obvious method for generating the points of an oval—use a loop that generates sin(x) & cos(x) coördinate-pairs—has already been mentioned. What's *not* so obvious, is that the points generated by that method are not evenly spaced! Not unless you're working with a perfect circle, anyway. For non-circle ovals, the distance between any two consecutive points will rise with the distance between those points and the origin. So if you're using those points in a "move [whatever] to the points of"-type command, the thing you're moving will not move at a constant speed… well, not unless your 'oval' is a circle, in which case the distance to the origin will be constant, hence the resulting speed of motion will also be constant.

The closer your 'oval' is to a perfect circle, the less obvious the deviations from constant speed will be, of course. You'll have to decide for yourself whether those deviations are of great-enough magnitude to be worth worrying about.

If deviations from constant speed *are* worth worrying about? Depending on what you're actually doing, you may actually want to have the oval-path-constrained motion vary in speed, and the particular mode of variance you end up with may be exactly the mode of variance you get from using the obvious method. But in any other case, you may want to look into a different method for generating the set of oval-points you use.

   
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