Taking Control of the AutoCAD Display

Taking Control of the AutoCAD Display
By now, you should be familiar with the Pan and Zoom functions in AutoCAD. Many other tools
can also help you get around in your drawing. In this section, you’ll get a closer look at the ways
you can view your drawing.

Understanding Regeneration and Redrawing
AutoCAD uses two commands for refreshing your drawing display: drawing regeneration (Regen)
and Redraw. Each command serves a particular purpose, although it may not be clear to a new user.
To better understand the difference between Regen and Redraw, it helps to know that AutoCAD
stores drawing data in two ways:
◆
In a database of highly accurate coordinate information that is part of the properties of
objects in your drawing
◆
In a simplified database used just for the display of the objects in your drawing
As you draw, AutoCAD starts to build an accurate, core database of objects and their properties.
At the same time, it creates a simpler database that it uses just to display the drawing quickly.
AutoCAD uses this second database to allow quick manipulation of the display of your drawing.
For the purposes of this discussion, I’ll call this simplified database the
virtual display
because it’s
like a computer model of the overall display of your drawing. This virtual display is in turn used
as the basis for what is shown in the drawing area. When you issue a Redraw command, you’re telling
AutoCAD to reread this virtual display data and display that information in the drawing area.
A Regen command, on the other hand, tells AutoCAD to rebuild the virtual display based on information
from the core drawing database.
You may notice that the Pan Realtime and Zoom Realtime commands don’t work beyond a
certain area in the display. When you reach a point where these commands seem to stop working,
you’ve come to the limits of the virtual display data. To go beyond these limits, AutoCAD must
rebuild the virtual display data from the core data; in other words, it must regenerate the drawing.
You can usually do this by zooming out to the extents of the drawing.
Sometimes, when you zoom in to a drawing, arcs and circles may appear to be faceted instead
of smooth curves. This faceting is the result of AutoCAD’s virtual display simplifying curves to
conserve memory. You can force AutoCAD to display the curves in a smoother curve by choosing
View 
Regen.

Controlling Display Smoothness
As you work in AutoCAD, you may notice that linetypes sometimes appear continuous, even when
they’re supposed to be dotted or dashed. You may also notice that arcs and circles occasionally
appear to be segmented lines, although they’re always plotted as smooth curves. A command
called Viewres controls how smoothly linetypes, arcs, and circles are displayed in an enlarged view.
The lower the Viewres value, the fewer the segments, and the faster the redraw and regeneration.
However, a low Viewres value causes noncontinuous linetypes, such as dashes or center lines, to
appear continuous, especially in drawings that cover very large areas (for example, civil site plans).
Finding a Viewres value that best suits the type of work you do will take some experimentation. The
default Viewres setting is 1000. You can try increasing the value to improve the smoothness of arcs and
see if a higher value works for you. Enter
Viewres
↵↵
at the command prompt to change the value. If you
work with complex drawings, you may want to keep the value at 1000; then, when you zoom in close to
a view, use the Regen command to display smooth arcs and complete linetypes.

Creating Multiple Views
So far, you’ve looked at ways to help you get around in your drawing while using a single view window.
You can also set up multiple views of your drawing, called
viewports
. With viewports, you can display
more than one view of your drawing at one time in the AutoCAD drawing area. For example, one viewport
can display a close-up of the bathroom, another viewport can display the overall plan view, and yet
another can display the unit plan.
When viewports are combined with AutoCAD’s Paper Space feature, you can plot multiple views of
your drawing. Paper Space is a display mode that lets you paste up multiple views of a drawing, much
like a page-layout program. To find out more about viewports and Paper Space, see Chapters 16 and 23.