Are you tried of the normal rectangular viewports ? You may be wondering if you can create viewports in irregular shapes such as polygonal viewports or circular viewports, here is how.
1. Switch to Layout Space and draw a circle next to the default viewport,
2. Enter -VPORTS, and press Enter, then we get the following prompt,
You might have noticed that entering VPORTS will pop up the Viewports dialog box,but with a hyphen, the dialog box will not pop up, instead the above prompt show up,
(See how a hyphen makes things different in CAD, check this post https://blog.gstarcad.net/whats-the-meaning-of-a-dash-or-hyphen-before-the-name-of-a-command/)
3. Enter O, press Enter, and select object to clip viewport.
4. Select the circle we just created, voila, you’ve created a circle viewport, shown as below,
Voila, we have made a circular viewport.
You can repeat the command and enter P to have a polygonal viewport.