Friday, December 5, 2008

AutoCAD limits

What are the limits in AutoCAD? I’m not talking about AutoCAD limits in functionality (there are) but rather the command “limits”. Here are probably most things worth knowing about limits mentioned. If I forgot something please add a comment.

Command: limits
Reset Model space limits:
Specify lower left corner or [ON/OFF] <0.0000,0.0000>:
Specify upper right corner <420.0000,297.0000>:

Here are some things related to these limits.

LIMITS sets and controls the limits of the grid display in the current Model or layout tab.

The command can be called transparently using 'LIMITS.

When limits checking is on, you cannot enter points outside the grid limits. Because limits checking tests only points that you enter, portions of objects such as circles can extend outside the grid limits.

This is what it will look like:

Command: LINE
Specify first point:
**Outside limits

In Drafting Settings (DSETTINGS) you can force the grid to display beyond the limits.

Drafting Settings

The STATUS command shows the limits among other things:

Command: status
121 objects in Drawing1.dwg
Model space limits are X:    0.0000   Y:    0.0000  (Off)
                       X:  420.0000   Y:  297.0000

The limits are saved in each drawing through the drawing variables LIMMIN and LIMMAX.

LIMMIN stores the lower-left grid limits for the current space, expressed as a world coordinate. LIMMIN is read-only when paper space is active and the paper background or printable area is displayed.

LIMMAX stores the upper-right grid limits for the current space, expressed as a world coordinate. LIMMAX is read-only when paper space is active and the paper background or printable area is displayed.

You can plot using the limits but only in model space (TILEMODE=1).

You can zoom to limits using a macro like this:
'_zoom _w (getvar "limmax") (getvar "limmin");

Zoom All displays the entire drawing. If the objects extend beyond the limits, Zoom All displays the extents of the objects. If the objects are drawn within the limits, Zoom All displays the limits.

If your drawing has no objects, Zoom Extents zoom to the drawing limits.

One great usage of LIMITS and the GRID I have found is when working in 3D as it will make it easy to find the “floor” when navigating around using commands like 3DORBIT and the like.


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