🚀 go-pugleaf

M,

I agree with the request for a better ellipse tool, and for a proper arc tool instead of the practically useless one AI presently has. (They should both be combined in a single tool, as in FH and Draw.) However:

      Before anyone gets upset, let me say I KNOW that AI draws circle-shaped
      and arc-shaped polylines.




Describe exactly what your definition of a "polyline" is.

AI, (like FH) neither draws "polylines" nor "circles." It draws Bezier paths. Circular paths are approximated by four Bezier paths.
It does not necessarily follow, just because the interface prompts the user for height and width (which I agree is lame) for an ellipse, that the program is using whatever you mean by "polyline" as its drawing method.

For example: I have an AI Javascript which lets me call for an ellipse the way a drafter would: in terms of major diameter and "angle". (Ex: a 1" 35 degree ellipse.) That doesn't mean the actual way AI draws the resulting path is any different. (It isn't; it's still just drawing four Beziers.) My Javascript just effectively provides a different interface.

Another example is a Javascript that lets one define an equilateral polygon by its side length, instead of its "diameter". Again, there is nothing different about the actual math AI uses to draw the resulting path. Illustrator is still just drawing Bezier curves; I've just injected a multiplication factor.

Similarly, AI's ellipse dialog could (and should) also provide different sets of user inputs for specifying the desired ellipse or arc. (Ex: Radius, Arc, start angle, end angle.) Adobe owns FreeHand's better treatment and could similarly replicated it in AI; were it not for AI's still not providing live geometric shape primitives.

      A circle is defined as a set of points the same distance from a center
      point, its radius.




Yes, that's the definition of a circle. By that definition, Illustrator couldn't draw one if it wanted to. Your monitor displays a rectangular array of pixles. A printing device renders a set of fixed printer spots. Neither of those conform to the definitive requirements of "a circle."

So even programs that do provide the dimensional inputs you desire (ex: Draw, Canvas, FreeHand, CAD programs) effectively draw what I think you are calling a "polyline"--the curve is aproximated by a set of straight line facets which are, in turn, approximated by lighting up the nearest monitor pixels or printer spots or plotter stepper motor increments. (Anyone who has ever imported a DXF into Illustrator has seen this.)

      It is manipulated by changing the radius, diameter, circumference, or
      a combination.




Now you're talking about manipulation, not definition. Manipulation is interface. It has nothing to do with whether AI constructs the ellipse and arc with Beziers or with other curve definition math. It's just a matter of what inputs you want to provide the user.

      It is not defined by its x,y dimension.




Now you're talking about definition again. No, a height value and a width value do not define a circle. But those values can be employed as the user inputs for scaling the results of a math algorithm that generates curves--whether that math is Bezier, or whether it's something else you call "polyline."

This is just one example of what I'm taking about when I charge that these so-called "illustration" programs are really mere page design programs. They don't allow the illustrator to think like an illustrator; they tyrannically force the illustrator to reference everything to the vertical and horizontal edges of the page, rather than the construction axes of his actual drawing.

But it doesn't have to be that way, just because AI constructs curves by Beziers.

JET