The perspective imaging program built
into AutoCAD will prove itself easier to do than manually constructing
a perspective drawing of your project the old fashion way. AutoCAD's
command stands for "Dynamic VIEW." This means that as you manipulate the
parameters of perspective, you will be able to dynamically adjust your
view and the appearance of the drawing. This gives you a very powerful
ability to select the most pleasing view of the group of buildings.
The first step is to bring the drawing
back into the plan view. Make sure that you are in the World Coordiante
System - type UCS<RET><RET> (note the two carriage returns).
Then type PLAN <RET><RET> (note the two carriage returns).
Zoom to extents, and then zoom to half of the extents by typing Z
<RET> .5X <RET><RET>.
Type DV<RET> on the keyboard
(or select "View" from the pull-down menu then "3D Dynamic View").
At the prompt "Select Objects:"
select the area of the drawing you want to view during the preparation
of the perspective viewing by selecting objects by placing a "window" around
the entire drawing image.
At this point you will successively select
the "TArget" point (where you are looking toward), and the "CAmera" point
(where you are looking from). To do this, type PO <RET> (this
stands for "POints"). You will be prompted to select the location of the
"TArget" point first. Pick one corner of the building as your "TArget"
point. Then you will be prompted to select the "CAmera" point in the same
manner. The "CAmera" point means where your eye is placed in relation to
the "TArget" point. In this exercise, to set the "CAmera" point, pick the
diagonally opposite corner of the building for the "CAmera" point. The
view will automatically change to align with the camera to target vector.
Note that both target and camera are located at the ground level ("0" height
Next you will adjust the distance
between the "CAmera" point and the "TArget" point. Type D <RET>.
This will bring up a slider bar at the top of the screen where you can
slide a pointer left or right until you have a satisfactory size to the
image. The Distance command will place your eye on the diagonal line established
by selecting the "TArget" and "CAmera" POints, but will increase or decrease
the actual distance between them. The "TArget" remains where it was set,
and the "CAmera" moves along the line. The effect is that the object you
are looking at will become smaller or larger. Once the Distance between
the "TArget" and "CAmera" has been set, AutoCAD will switch to perspective
viewing, so that parallel lines converge, and vanishing points are established.
Next you will change the angle of the
line between the "CAmera" point and the "TArget" point, through the "CAmera"
command. Type CA <RET> then move the mouse to fly up and around
the perspective dynamically. Do not dip the cursor below the center
of the screen, or you will be looking from under the drawing.
If you need to enlarge the image on the
screen, you can change the distance again - type D<RET>
and use the slider bars. You cannot use the standard AutoCAD Zoom
command. The DVIEW Zoom command is different from the standard
AutoCAD "Zoom" command - it allows you to change the length of your imaginary
lens in your imaginary camera, that is the lens to film distance.
As you might expect, a 50mm lens is a so-called "normal lens," a 30mm lens
is a "wide angle," for example, and a 800mm lens is a "telephoto lens."
Note that as you move your pointer mouse back and forth over the slider
bar the status line shows the resultant lens length, and the view will
dynamically change to show you what it will look like. The results of the
view in terms of potential distortion will follow that of an actual camera.
What is actually happening is that the "cone of vision" widens with a shorter
lens, and narrows with a longer lens. The DVIEW Zoom command does not affect
the distance between the "CAmera" point and the "Target" point. This command
will possibly take some time to get used to. You should try out various
lens lengths to see how it varies the perspective view. I suggest a relatively
short lens length, say about 30 mm, because it increases the dramatic angularity
of the perspective.
Type <RET> to end the perspective setup.
This will bring you back to the Command: prompt and out of the perspective
imaging program. The drawing will still appear in perspective view,
and you will not be able to edit it. You will need to return to an
orthogonal view (i.e., a non-perspective view) to edit your drawing.
Once you are pleased with your perspective
view and you are through tinkering with it, you should save it as a memorized
"view." To do this, type V <RET>. This will bring up the
"View Control Dialogue Box." Select the "New" button. Type in the
name of this view P1. Then pick the "Save View" button. Then
pick the "OK" button. This view in its perspective mode will then
be able to be brought back "restored" in any viewport.
To allow editing of the drawing, you should
return to the "plan" view by typing PLAN <RET><RET>.