How to lock scale of nonrectangular viewports and more about viewports in AutoCAD

If you usually work with the Properties palette you might wonder how to lock the scale or access other properties on nonrectangular viewports.

Here is when a rectangular viewport is selected.

But when a nonrectangular viewport is selected it looks like this.

The reason for this is that a polyline is added and works as a clipping entity for the viewport. What you need to do is to take the extra step and in the drop-down box where it says All (2) select Viewport (1).

Now you can see that the properties are available.

A quicker way though is to select the viewport, right-click and select Display Locked>Yes. 

Here is a little about viewport locking from the help documentation.

By locking the viewport scale first, you can zoom in to view different levels of detail in your viewport without altering the viewport scale.

Once you set the viewport scale, you cannot zoom within a viewport without changing the viewport scale. By locking the viewport scale first, you can zoom in to view different levels of detail in your viewport without altering the viewport scale.

Scale locking locks the scale that you set for the selected viewport. Once the scale is locked, you can continue to modify the geometry in the viewport without affecting the viewport scale. If you turn a viewport's scale locking on, most of the viewing commands, such as VPOINT, DVIEW, 3DORBIT, PLAN, and VIEW, no longer function in that viewport.

NoteViewport scale locking is also available for nonrectangular viewports. To lock a nonrectangular viewport, you must perform an extra step in the Properties palette to select the viewport object rather than the viewport clipping boundary.

On the topic of viewports.

• The clipped viewports or so called nonrectangular viewports on the images where created using the MVIEW command and then selecting extisting polyline objects. Objects allowed are a closed polyline, ellipse, spline, region, or circle. The polyline you specify must be closed and contain at least three vertices. It can be self-intersecting, and it can contain an arc as well as line segments.
• Here is a patent on Reactor-based viewport clipping using arbitrary graphical entities.
• Viewports where introduced with AutoCAD R11.
• Nonrectangular Viewports where introduced with AutoCAD 2000.
• New viewport layer properties where introduced with AutoCAD 2008. These new properties enable you to apply layer properties on a per-viewport basis. Independent LT scale per viewport. Viewport Layer Freeze. The new annotation functionaly makes it possible to display objects differently in individual viewports.
• Create a polyline in modelspace based on a viewport.
• Speed up your work when you work with viewports.
• The undocumented SPACESWITCH system variable makes it possible to lock usage of double-click to enter into model space.
• AutoLISP sample code to get viewport scale even for clipped viewports.
• AutoLISP freeware program VPlayers.lsp to save, load, copy layer settings per viewport.
• AutoLISP code vpsel.lsp to select all visible objects in selected or active paperspace viewport.
• Creation of viewports using AutoLISP.
• The readme for AutoCAD 2008 has things to say about viewports that is good to know.