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I am using Data CAD 20 LT and have been working with creating voids in hatching in 2D. So far, I have had no problem creating rectangular/circular-shaped voids from the polyline menu, but how do I create ellipse-shaped voids or other shaped voids for that matter? I appreciate any light that can be shed on this question...

An ellipse you can turn on the Knock Out setting to make that work. Can also do that to circles.
If you have a set a lines/arcs/curves, you should be able to go to the polyline edit menu, and select the S3 Line to Poly command, and join any set of connected entities into a polyline which then can become a void.

The best way to have an elliptical void, is to draw the ellipse, and then trace it with the 4 arcs that approximate it. You can draw a polyline, and then convert it to a void, or create a new void with 3-point arcs.

I have tried to find out about KnockOuts and haven't found any info. in the manual. Also, I have tried to use the edit polyline menu to convert an ellipse into a polyline and convert does not come up on the menu. I have 20LT. I believe the manual shows it is only available on the full version.

I have tried the second method suggested, but haven't been able to get the 3-point arc to match the ellipse close enough. I would know how to convert the new ellipse-shaped polyline to a void if it would close as one polyline. I am not so sure that it will take four separate segments of polyline and make it one closed polyline with this approach. I do thank both of you very much for your help with this, although I am still searching for the answer to my question...

Strange, you are correct, not much in the manual about it. Look here https://is.gd/zgtEBd
Think of Knockouts are like a special type of void, they mask over anything that is before it in the drawing file.
Yes, for some reason you can not make a ellipse directly into a polyline. Work around is to make the ellipse, go to 3d menu, explode to 3dlines, go to polyline menu, and use F2 Cont Search inside the lines and it will become a polyline. You will need to delete the 3dlines, erase by area, left 1/2, right 1/2 of area.
Now the polyline can become a void.

Strange, you are correct, not much in the manual about it. Look here https://is.gd/zgtEBd

There is also an informative article by Clay Rogers regarding knockouts at https://www.datacad.com/bbs/viewtopic.php?f=58&t=16566 (in the Priority Service Plan area of the forum, so not sure if you will have access to it ... but worth reading if you do).

I have struggled to fully understand knockouts in the past. There is some information in the 'Whats New' document (apparently functionality added to Datacad in the last several years is documented in this document instead of in the actual manual). My understanding was helped a bit by a post from Josh Huggins (https://www.datacad.com/bbs/viewtopic.php?f=71&t=16624&p=75081#p75079) in a 'Knockout Voids'thread on this forum a few months ago.

Thank you for the additional information! I have tried, and am in the process of trying these methods. The Knockout Sheet was helpful in understanding what they are for. Still am trying to locate the keystrokes to go about it. I just tried the ellipse exploding into lines in 3D, everything moves forward until the contour search. That function is not available in 20LT. Will continue drilling down with Knockouts. I have waded through the steps on the illustration from your other post from Josh. I really appreciate your help on this and will continue trying...

Approximate Ellipse
I don't think anyone mentioned this yet, but you can create an approximate ellipse out of multiple arcs via the Ellipse menu. Toggle on Approximate and set the number of arcs per quadrant. Use less for 'fat' ellipses and more for 'thin' ellipses.

Mark, how long has that feature been hiding? The best part is, that the "approximate" ellipse can then be converted to a polyline - which can be turned into a void!

Mark's tip may have lead me to another way that shaves 2 milliseconds off of his technique

1. Create the ellipse with the "approximate" menu item in the ellipse menu in Curves menu.
2. Using DCSPRINT macro and the Lin2Pln function, window around the ellipse.
3. In the Polyline menu, select the hatched area, then Add Voids, and then select Voids and then window around the ellipse.

You should get what I show here.

You don't need the DCsprint macro - the Line To Poly in the Polyline / Edit menu does this, too.

Neil Blanchard wrote:...how long has that feature been hiding?

This feature first appeared in DataCAD 18.01.00 Subscription.

Mark and Neil's information has been helpful, but still having a problem with the void process. Even though I do not close the polylines, it wants to show all four segments closed in the add void process. What am I doing wrong? Maybe the problem is in the grouping of the four segments or the original ellipse below. I am drawing the 2D ellipse with approximate setting of 2 per quadrant. Then, I am drawing a polyline over the top with the curves 3 Pt Arc. Lastly, I group the polyline segments and add void. Each original polyline shows a closed polyline or, in other words, a line connecting the start and finish of each arc. I am close, but not quite there. Thank you, I appreciate all your help!

Hi Eric,

If you draw the ellipse with the Approximate toggled on, and the convert that to a polyline with the Line To Poly function, you then just need to select that as a void. If part of the ellipse is outside the perimeter of the hatch, then that isn't a void - it is part of the perimeter.

Can you post a screen grab of what you are trying to do? You can use Alt-Print Screen to get it on the computer's clipboard, and then Paste it in a image editor, and save it to you hard drive. Then upload it as an attachment to your post, and show it inline.