A ray is a line in three dimensional space that starts at a point and extends to infinity. Because rays extend to infinity, they are not calculated as part of the drawing extents. The default method for drawing a ray is to select the start point of the ray and then specify its direction.
You can draw a ray in any of the following ways:
Horizontal draws the ray parallel to the x-axis of the current user coordinate system (UCS).
Vertical draws the ray parallel to the y axis of the current UCS.
Angle draws the ray parallel to a specified angle.
Bisect draws the ray perpendicular to an existing object.
Parallel draws the ray parallel to an existing object.
To draw a ray
Choose Draw > Ray.
Specify the start point.
Specify the direction.
To complete the command, press Enter.
Command line RAY
Start point (A) and direction (B).
LINE: Creates straight line segments
RAY: Creates a semi-infinite line
XLINE: Creates an infinite line
System Variables Reference