CONSTRUCT SPACE CURS-SHPE Control

This command enables coordinates input by cursor to be projected onto a previously defined shape.

Control	Comments
DEFAULT	The default mode of operation in which the out of screen (z)
	coordinate of cursor input is calculated as the projection of the
	cursor hit onto an xy plane of z=0. If this plane is normal to the
	screen then the out of screen (y) coordinate is calculated as the
	projection onto a zx plane of y=0. If this plane is normal to the
	screen then the out of screen (x)coordinate is calculated as the
	projection onto a yz plane of x=0.
Z 'real'	Specify that the out of screen coordinate of cursor input be
Y 'real'	calculated as the projection on to a plane parallel to a coordinate
X 'real'	plane and displaced by distance `real'.
Shape_name	Enables the z coordinate of cursor input to be calculated from
	the projection of the cursor hit onto a previously defined shape.
	Shapes may be defined using the command
	CONSTRUCT SHAPE. The z coordinate is calculated to
	lie on the specified shape at its intersection with an imaginary
	line drawn perpendicular to the screen from the cursor hit
	position. If this line intersects the shape twice then the position
	nearest to the view point is taken.