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*MonkeyJump
Message 1 of 3 (22 Views)

ellipses in QC7

22 Views, 2 Replies
02-14-2000 02:56 PM
When a narrow ellipse is drawn and you zoom in at one of the narrow
ends, it is quite visible that the ellipse is drawn using straight line
segments. I decided to check to see if internally the ellipse was
defined precisely, so I drew a line through one of the ellipse's
straight segments and tried to snap using the intersection snap. When I
did this, the autosnap snapped to a point outside of the straight-edged
ellipse at a point that was "theoretically" on the ellipse. So in effect
we have QC7 drawing ellipses ( I imagine circles included ) using
straight line segments to the screen, but internally treating them using
precise function definitions. Nice to know. Now I just wish I knew how
splines and fitted curves were treated internally too.
*lscad
Message 2 of 3 (22 Views)

Re: ellipses in QC7

02-14-2000 03:40 PM in reply to: *MonkeyJump
Tools-Drawing Options-Drawing-Ellipse Segments (#bet. 3--1999)

MonkeyJump wrote:

> When a narrow ellipse is drawn and you zoom in at one of the narrow
> ends, it is quite visible that the ellipse is drawn using straight line
> segments. I decided to check to see if internally the ellipse was
> defined precisely, so I drew a line through one of the ellipse's
> straight segments and tried to snap using the intersection snap. When I
> did this, the autosnap snapped to a point outside of the straight-edged
> ellipse at a point that was "theoretically" on the ellipse. So in effect
> we have QC7 drawing ellipses ( I imagine circles included ) using
> straight line segments to the screen, but internally treating them using
> precise function definitions. Nice to know. Now I just wish I knew how
> splines and fitted curves were treated internally too.
*MonkeyJump
Message 3 of 3 (22 Views)

Re:

02-14-2000 05:05 PM in reply to: *MonkeyJump
ya............so?

Did you notice the mistake in QuickCad7 ? The help message for
"Tools-Drawing Options-Drawing-Ellipse Segments" states:

To change the number of segments used when converting an ellipse to a
polyline/polygon, type a number in this box. The default number is 36.
Lower values result in rougher polygons, but they redraw faster and
require less drawing memory.

.... when in reality, it should read:

To change the number of segments used when converting an ellipse to
CURVES, type a number in this box. The default number is 36. Lower
values result in rougher polygons, but they redraw faster and require
less drawing memory.

For some reason or other, when you convert an ellipse to a
polyline/polygon and then explode it you always get 16 polyline
segments, regardless.

lscad@jps.net wrote:
>
> Tools-Drawing Options-Drawing-Ellipse Segments (#bet. 3--1999)
>
> MonkeyJump wrote:
>
> > When a narrow ellipse is drawn and you zoom in at one of the narrow
> > ends, it is quite visible that the ellipse is drawn using straight line
> > segments. I decided to check to see if internally the ellipse was
> > defined precisely, so I drew a line through one of the ellipse's
> > straight segments and tried to snap using the intersection snap. When I
> > did this, the autosnap snapped to a point outside of the straight-edged
> > ellipse at a point that was "theoretically" on the ellipse. So in effect
> > we have QC7 drawing ellipses ( I imagine circles included ) using
> > straight line segments to the screen, but internally treating them using
> > precise function definitions. Nice to know. Now I just wish I knew how
> > splines and fitted curves were treated internally too.

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