Visualizing 3D Models - Autodesk AutoCAD 2013 Practical 3D Drafting and Design - page 43

thographic coordinate system, so the working XY plane becomes parallel to the view.
This behavior may be undesirable and can be turned off by assigning the value 0 to
the UCSORTHO variable. This variable is saved in the registry and doesn't depend on
drawings.
The Viewport controls
Since Version 2012, in the top-left corner of the viewport, by default, there are three
controls. The second one allows the activation of the predefined or saved views.
Viewport controls are presented later.
The PLAN command
This command directly activates the Top view for the current coordinate system (de-
fault), any saved coordinate system, or the world coordinate system. It processes the
ZOOM command's Extents option in the model.
The VPOINT and DDVPOINT commands
Two more commands are available for changing the viewing direction:
• VPOINT : This command (alias -VP ) defines the viewing direction by a
vector that connects a point to the origin. The command just asks for this
point. For instance, looking at the origin, 0,0,1 indicates that we are on
the Z axis; it means this is the top view. The ZOOM command's Extents
option is always processed, so 0,0,2 will give exactly the same result.
1,1,1 means that we are at the same distance from all the positive axes
( Northeast Isometric ). This command has the advantage of replicating
a precise non-orthographic view. The other options are less important.
• DDVPOINT : This command (alias VP ) shows a dialogue box where the
viewing direction is defined by two angles, the first on the plane from the
X axis, and the second from the XY plane. We can enter these values or
just pick on the images.