3-D CITY IN PERSPECTIVE WITH WINDOWS
This is an exercise in developing your
drawing of an imaginary city, using 3D FACE commands to create windows
and the DVIEW command to set up perspective views. The end result will
be a drawing which will be plotted on the HP Laser Jet printer.
END OF EXERCISE NO. 9
Start up AutoCAD.
Open exercise no. 8, and save it
as "[your initials]9.dwg.
You are now going to add windows and doors
to each side of the buildings and skylights to one of the roofs, and then
view and plot it in true perspective.
Turn Tilemode On to temporarily put away
the paper. Select from the Pull-down menu "View" then "Tilemode."
Do one building at a time. This is where
having each building on a separate layer will come in handy so you can
freeze and thaw layers to be able to work on one layer at a time. Freeze
the C-WALK layer on which the hatch pattern of the ground plane is drawn
to eliminate the possibility of making a mistake in snapping to the wrong
If it is not already showing on the drawing,
turn the UCSICON on and set it at the Origin of the UCS. To do this, select
from the Pull-down menu "View" then "Display" then "UCS
Icon" then make sure that both the "On" and "Origin"
Create a "User Coordinate System" parallel
to a vertical face of one of the buildings. To make the UCS, type UCS
<RET> 3 <RET> and pick the three corners of the vertical plane.
Save this UCS to a name. To do this, type
"DDUCS" then pick on the word *NO NAME* in the list. Then
hold down the left button of the mouse and highlight the word *NO NAME*
in the box to the right of the "Rename to:" button and type in a
new name for this UCS. Make up a name that will be descriptive enough so
that you can identify what it refers to later. Do not include any spaces
in the name. Then click on "OK."
Set the current thickness to 18"
and set the current elevation to -18". This will make your windows
appear to have some depth to them. To do this, type ELEV <RET>
<RET> -18 <RET>
Draw one rectangular window on the side
of this building. Array that window in a rectangular array in both directions
(across and up) in such a fashion that they will look well proportioned
to the size of the building.
Draw 3D Faces between each window. Remember
that 3D Faces can only be either 3 sided or 4 sided flat planes. You
should do the least work possible. Try to do only one 3D Face between
windows and array that entity to fill in the other spaces. Also, since
the building is symmetrical on each face, you could possibly draw only
half of the building and then mirror that half to the other side of the
wall. Where the 3D Faces need to be invisible because they are next to
other 3D Faces to fill an irregular area, you will need to precede the
selection of the next point in drawing the invisible with typing the letter
<RET>. If you need to see all of the invisible lines for some reason
(to see where you may have made a mistake, for instance), you need to set
the AutoCAD variable "splframe" to 1 (that is "on"). Do this
by typing splframe <RET> 1 <RET>. To make them invisible
again, simply turn the variable splframe back to 0 ("off"). Do this
by typing splframe <RET> 0 <RET>. Note that once a
3D Face has been drawn, the only way to change the visibility of an edge
is to use the "Modify" "Properties" command from the Pull-down menu. Select
"Modify" then "Properties" then pick the 3D Face of you want
to change the visibility of one or more of the edges. The "Modify 3D Face"
Dialogue Box will appear. The bottom of this Dialogue Box shows the visibility
of each face. A check mark in one of the boxes means that face is visible.
To make it invisible, just remove the check by picking in the box.
After you finish drawing the windows and
the 3D Faces on one of the 4 walls, make a block out of that side of the
building and insert it back to the same side on which it was drawn. That
will give you the capability of universally changing all sides of the building
by simply re-defining that block later on, if you wish.
Make the World UCS current by typing UCS
Polar Array the block you just
made around the center of the building in plan, with a number
of items = 4 and the angle to fill = 360 degrees (the default).
Using the "Modify" "Properties" command,
change the thickness of the original extruded rectangle making up the sides
of the building to zero. This will allow the windows to be seen through.
You are now going to use the AutoCAD perspective
system to study this more detailed drawing in true 3d. The perspective
imaging program built into AutoCAD is difficult to get used to, but when
you do you will find that it has some very powerful capabilities. In any
event, it will prove itself easier to do than manually constructing a perspective
drawing of your project the old fashion way. AutoCAD's DVIEW 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 to the plan view. Make sure that you are in the World Coordiante System
and 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 DVIEW<RET> on the keyboard
or by selecting "View" from the pull-down menu then "3D Dynamic
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. The drawing of the city block in this exercise
is simple enough to allow dynamic viewing of all the objects.
At this point you will successively select
the "TArget" point (where you are looking to), and the "CAmera" point (where
you are looking from). To do this type PO (this stands for "POints").
will be prompted to select the location of the "TArget" point first. Pick
one corner of the site as your "TArget" point. First filter out the x and
y coordinates by typing .XY <RET> prior to OSNAPping to the point.
When you pick the point with the aperture, you will see the prompt "(need
z)." Respond to this by typing 0 <RET> (you are setting the
height of the TArget on the xy plane at 0 feet). 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 object and the
"TArget" point. In this exercise, to set the "CAmera" point, pick the diagonally
opposite corner of the site for the "CAmera" point, first filtering out
To respond to the question "(need z)," type in 200' <RET>.
This will place your eye above the tallest building, so you will see the
whole city from the air.
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 appearance
to the perspective. 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, or, if
the line of vision is not truly in the center of the object, it may disappear
altogether. The spread of cone of vision remains the same as you change
the Distance. Suggested distance is 1000 feet. 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.
If you need to "zoom in" closer you may
use the Zoom command within DVIEW. You cannot use the standard AutoCAD
Zoom command. The DVIEW Zoom command is different from the standard
AutoCAD "Zoom" command in that it allows you to change the length of your
imaginary lens in your imaginary camera. 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. Suggested lens length for this exercise is 40mm.
To get this, simply type in 40<RET> instead of selecting a number
from the slider bar.
Next you may want to change the angle
of the line between the "CAmera" point and the "TArget" point, through
the "CAmera" or the "TArget" commands in DVIEW. The "CAmera"
command will bring up two bars in succession, first a vertical bar on the
right side of the screen which will allow you to change the angle of the
line between the "CAmera" point and the "TArget" Point, with relation to
the xy plane. If you like the angle as it was, simply make a "null" response
(that is a Carriage Return). After the vertical adjustment is made, a horizontal
slider bar will appear on top of the screen. You can then visually ("dynamically")
change the angle of the line of vision in the xy plane from the x axis.
Once you are pleased with your perspective
view and you are through tinkering with it, save it as a view. To do this
select from the Pull-down menu "View" then "Named View..."
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.
Create and memorize at least three perspective
Turn Tilemode off to bring back the viewports
and sheet title.
Restore one of the saved perspective views
in each of the four viewports. There should be a plan view and three perspective
or isometric views in four viewports.
Plot this drawing using the HP 350C plotter.
Plot the drawing in Paper Space just like Exercise No. 8.
Copy your drawing to your floppy disk.
Place your floppy disk in the A: drive of the computer. Copy the drawing
from the hard drive to your floppy disk by using the Windows Explorer.