|
Desiring God The Spurgeon Archive Last Issued
Ref.Issue #1
Ref.Issue #2
Ref.Issue #3
Ref.Issue #4
|
|
Ref. Issue #5 - 19 May 2008 - Using DVIEW
Using DVIEW to a Create a Perspective View
The original command for defining views with perspective from any angle and distance was
DVIEW. The newer 3D Orbit feature is easier to use than DVIEW, but you may still find DVIEW
helpful for its precise ways of defining a view. DVIEW is also useful if you want to create 3D
views using AutoLISP or VBA. Note that the DVIEW command has been removed from
AutoCAD LT.
Like 3D Orbit, DVIEW uses the metaphor of a camera. There is a camera point (where you are
standing) and a target point (what you are looking at). By defining these two points, you can
create either close-up or distance views, much as you would with the zoom or panoramic
lens of a camera. The DVIEW command creates both parallel and perspective views.
Using DVIEW
To create a perspective view, type dview ↵ on the command line. At the Select objects or <use DVIEWBLOCK>: prompt, select the objects that you want to include in the process of
defining the perspective view.
You should select as few objects as you need to visualize the final result if you have a complex
drawing. If you want to select the entire drawing, type all ↵ even if the current view
doesn’t display the entire drawing.
Press Enter if you don’t want to choose any objects. The command substitutes a block called
dviewblock, which is a simple house. You can use the house to set your perspective view.
If you want, you can create your own block and name it dviewblock. Create it with X, Y, and
Z dimensions of 1. When you press Enter at the Select objects or <use DVIEWBLOCK>:
prompt, the command looks for dviewblock and uses it to display the results of the perspective
view settings.
Understanding the DVIEW options
When you start DVIEW, you see the following prompt. You use these options to define the
3D view.
Enter option
[CAmera/TArget/Distance/POints/PAn/Zoom/TWist/CLip/Hide/Off/Undo]:
Here’s how to use the DVIEW options:
✦ Camera: Specifies the angle of the camera, which represents where you’re standing.
You need to specify the angle from the X axis in the XY plane and the angle from the XY
plane. This is very similar to the way that you specify a view using the DDVPOINT command,
explained earlier in this chapter. At the Specify camera location, or enter
angle from XY plane, or [Toggle (angle in)] <35.2644>: prompt, type in an angle
from the XY plane, or move the cursor vertically to dynamically see the results. Keep in
mind that moving the cursor horizontally changes the angle from the X axis in the XY
plane. It can be confusing to change both angles at once, and so you can limit the effect
of your cursor movement to one angle with the Toggle suboption. At the Specify
camera location, or enter angle in XY plane from X axis, or [Toggle (angle
from)] <66.12857>: prompt, move the cursor horizontally to see your objects rotate
around you at a constant altitude. Now, your cursor affects only the angle from the X
axis. You can press Enter when you like what you see, or you can type in an angle.
✦ Target: Works exactly like the Camera option, except that it defines the angles for the
target of your viewpoint (what you would see through the camera lens). However, the
angles are relative to the camera position. If you’ve already set the camera angles, then
the target angles default to those angles that you create by drawing a straight line from
the camera angle through 0,0,0. As with the Camera option, use the Toggle suboption to
switch between the two angles that you need to specify.
✦ Distance: This option is very important because you use it to turn on Perspective
mode. Before you use this option, the views that you see are parallel views. When you
use the Distance option, you see a slider bar at the top of the screen. After you choose
a distance, the Perspective mode icon replaces the UCS icon if your UCS display is set
to 2D. At the Specify new camera-target distance <3.0000>: prompt, you can type
a distance from the camera to the target or use the slider bar. Move the cursor to the
right to zoom out. Moving the cursor to 4x is equivalent to using the ZOOM command
and typing 4x ↵. Move the cursor to the left of 1x to zoom in. The zoom factor is relative
to the current display, and so 1x leaves the zoom unchanged. You can also type a
distance in drawing units.
✦ Points: Define the camera and target by specifying two points. The command line displays
the Specify target point <0.3776, -0.1618, 1.0088>: prompt. The default
target point, which is different for each drawing, is the center of the current view. You
see a rubber-band line from the target point, which you can use to find your bearings
when choosing a new target point. You can also type a coordinate. At the Specify
camera point <-1.5628, 0.9420, 2.2787>: prompt, pick or type a point. You can use
the rubber-band line stretching from the target so that you can visualize the camera
and target points. Because it’s difficult to know which 3D points you’re picking, you
should use an object snap or XYZ point filters to pick points.
Although it is common to choose a target point on one of the objects in your drawing, you
often want the camera point to be off of the objects so that you’re looking at the objects
from a certain distance and angle. To pick the camera point, choose Format ➪Point Style
(before starting DVIEW) and choose an easily visible point style. Decide which elevation you
want, type elev ↵, and set a new elevation. From plan view, choose Point from the Draw
toolbar and pick a point. The point is created on the current elevation. Then use the Node
object snap to snap to the point when specifying the camera point in the Points option.
✦ Pan: At the Specify displacement base point: prompt, pick any point. At the
Specify second point: prompt, pick the point to which you want the first point to
pan. The model moves the distance and direction indicated by an imaginary line from
the base point to the second point.
✦ Zoom: The Zoom option displays the same slider bar that you see with the Distance
option, as I explained previously. If Perspective mode is not on, then you see the
Specify zoom scale factor <1>: prompt, which works like the Distance option slider
bar. If Perspective mode is on, then you see the Specify lens length <50.000mm>:
prompt. A shorter lens length, such as 35mm, zooms you out, giving a wider viewing
angle. A longer lens length, such as 70mm, zooms you in, giving a narrower viewing
angle. Although the prompt shows a default in the form 50.000mm, you can only type in
a number. Omit the mm.
✦ Twist: Turns your objects around in a circle parallel to the current view that you have
defined. The default is 0 (zero) degrees, which is no twist. Assuming your current view
looks at the objects right-side up, then 180 degrees turns the objects upside down, as
if you had turned the camera in your hands upside down. You see a rubber-band line
from the center of the view, which you can use to pick a twist point, or you can type in
an angle.
✦ Clip: Enables you to create front and back planes that clip off the view. Objects in front
of the front clipping plane or behind the back clipping plane are not displayed. You can
use the front clipping plane to clip off a wall in front of the camera, thus letting you see
through the wall to the objects beyond—a kind of CAD x-ray vision. Use the back clipping
plane when you want to exclude objects in the distance from your perspective
view. The clipping planes are always perpendicular to the line of sight, and so you only
need to set their distance from the target point. At the Enter clipping option [Back/
Front/Off] <Off>: prompt, specify Back or Front to set the back or front clipping
planes. Specify Off to turn off all previously defined clipping planes.
When you use the Distance option to create a perspective view, the option automatically
turns on a front clipping plane at the camera point.
• Front suboption: At the Specify distance from target or [set to Eye
(camera)/ON/OFF] <2.5682>: prompt, specify Eye to set the clipping plane
at the camera point. You can define the clipping plane by typing in a distance,
or using the slider bar that appears at the top of your screen. As you move the
cursor on the slider bar, stop to let the drawing redraw so that you can see the
result.
• Back suboption: At the Specify distance from target or [ON/OFF]<-5.5826>: prompt, specify On or Off to turn the clipping plane on or off, or
specify the distance as for the front clipping plane.
✦ Hide: Performs a hide, just like the HIDE command, thus letting you clearly see the
results of the view that you’ve created.
✦ Off: Turns off Perspective mode and returns you to a parallel view. Otherwise, when
you leave DVIEW after going into Perspective mode, your drawing retains the perspective
view until you change the view—for example, with VPOINT. Undo
✦ Undo: Undoes the effect of the last DVIEW option. You can undo through all of the
changes that you have made in DVIEW.
Source : AutoCAD2007 and AutoCAD2007 LT Bible
by Ellen Finkelstein
Thanks to the source
|
|
