The mathmatics of an oval are well know and can be looked up in Wikkipedia, so you could soon write a bit of VB script to give you the relative x,y positions. The problem is then running it on Mach3, becasue there is a circle command, which, I assume constantly changes the x in relation to y as the cutter moves, but that is all.
All other "shapes" come from many short lines, all joined up, not a smooth transition.
There must be a way to control say the x axis in relation to the y axis smoothly, becasue it is already done for a circle, but how you do that on the fly, so tp speak, with a different equation, I do not know.
We would certainly be getting beyoud the bounds of the original CNC machines then.