topic Re: Ellipse hole in POLY2 in Libraries & objects

Ellipse hole in POLY2

Bruce — Sun, 24 Sep 2017 03:41:46 GMT

Does anyone know how to create an ellipse hole in a POLY2 shape? I can create an ellipse by itself, and I can create a circular hole in a POLY2...but I can't figure out a way to do both smoothly.

I know how to run a loop command to create a series of lines that emulate an ellipse, but this is a series of lines, not a smooth ellipse.

I think I know the answer, but you never know...

Re: Ellipse hole in POLY2

Jochen Suehlo — Sun, 24 Sep 2017 14:01:42 GMT

I don't think that it is possible to get a smooth curve, because an ellipse is not a spline; I think you must use segmented poly-lines, where the points are positioned near enough to each other, that you cannot see the segmentation.
Isn't a circular POLY made with 4001 Mask-Value a segmented polyline as well?

Re: Ellipse hole in POLY2

Bruce — Sun, 24 Sep 2017 19:01:06 GMT

I don't know if a POLY2 with a 4000 mask is a series of lines or not...but I can't tell either on the screen or in a print out...and I don't have to define any RESOL to achieve this.

Never mind, with a step angle of 2°, and the below code, I've achieved the results I want.

FOR i = 0 TO 360 STEP 2
   PUT axis1/2*COS(i), axis2/2*SIN(i), 1
NEXT i

If I then use a HOTARC2, the user can snap to this ellipse as well, completing the illusion.

Re: Ellipse hole in POLY2

Laszlo Nagy — Thu, 28 Sep 2017 10:38:26 GMT

Bruce,

I would use exactly the same method as you did to achieve this.
I think that 2-degree value may be a bit high (it is equivalent to a RESOL value of 180 (360/180 = 2). A 10-degree value would achieve the default RESOL value (36).
Of course it depends on how large that ellipse is, so you may actually need that high resolution.

Re: Ellipse hole in POLY2

Bruce — Thu, 28 Sep 2017 19:04:31 GMT

Thanks Laszlo. I agree that it is a high resolution, but given I'm trying to mimic a smooth (not faceted) curve, and the processor overhead for 2D would be quite low, I'm not too concerned about it. I might revisit the appearance at a higher degree step, to see if it's acceptable at the desired output scale.