Hi Anthony,

> and yes by real life i mean make an approximate sketch with paper
> and some sort of drafting tools. what i'm really curious about is how
> a draftsmen would have went about this in the 1950's and if that
> method would work in moi. again, only out of curiosity, not to
> implement for daily use in moi.

I guess check out "The Draftsman's method" that's described here:
http://www.uwgb.edu/dutchs/MATHALGO/Ellipses.HTM

Seems to be an approximation based on sampling several points and then I guess connecting them with line segments - you can repeat the same steps in MoI if you want, but the result will be a polyline approximation of an ellipse and the approximation will be kind of rough as far as CAD accuracy goes.

An approximated sketch on paper is a lot different kind of a thing than actual geometry that you then want to use directly as a basis for further 3D construction in MoI.


> i have found several sketching methods for real life, and of
> course many equations to calculate points. i'm most curious
> if you can use lines and arcs to approximate an ellipse, possibly
> the five center method.

The five center method is described there as well, I was not familiar with it. Since it involves drawing circles, lines, and arcs and finding intersection points I think you should be able to repeat the process in MoI. The result will however be again by CAD standards a pretty rough approximation, probably without a known error bound, and will again be a segmented series of curves rather than just one smooth curve.

It would not be desirable to use a segmented approximation like that as the generator for further 3D shapes, because extrusions and stuff like that which you construct off of it will inherit the segmentation and inaccuracies as well.


So although you could use one of those old drafting methods for constructing some approximation of an ellipse in MoI, it would be a kind of pointless exercise since it would not work well to use the result for much of anything after that.

Meanwhile using one of the ellipse tools generates a mathematically exact ellipse that's made up of just a single totally smooth segment, with a lot less effort involved as well.

So I do not see how one of those methods would be very practical for use in MoI.

- Michael