PLANE allows you to define a selection plane, using 
orientation and depth. This method is especially useful 
for entities that are difficult to select, due to their 
placement (e.g., entities that lie on top of each other).

Only those entities that lie completely within the defined 
plane are selected.


Define the plane by choosing from the following options:

3 PTS - to define a plane using three positions in space.
Choose an option from the Position Menu to indicate the
position of each point.  Colinear points are not accepted.

PT LINE  - to define a plane using a point (or position) in 
space and a selected line entity. Indicate a position using
an option from the Position Menu, and select a line entity.

2 LINES - to define a plane using the endpoints of two
lines, and their 3-D intersection (or potential 3-D
intersection). Select two intersecting (or potentially
intersecting) lines.

VW/DPTH - to define a plane using a specified view and
depth. Enter a view number and specify a depth by entering 
a value or by indicating a position using an option from 
the Position Menu.

ENTITY - to define a plane using a selected line, arc,
conic, or 2-D spline. A line entity defines the plane as
being normal to the screen, at the same inclination as the 
line projected onto the screen.  An arc or spline entity 
defines the plane in the view of definition and at the 
depth of the selected entity. Select the desired line, arc,
conic, or 2 D spline.
