HROOF                                                      Menu: (HELPL) ADHLP
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Creates a help-line at the intersection of two planes.

         1.  (NUM) angle of first line
         2.  (NUM) angle of second line
         3.* (POINT) intersecting point of lines
         4.* (POINT) point on first line
         5.* (POINT) point on second line

Description
This command creates a help-line at the intersection of two planes.  Each
plane is defined by a line (usually the top base of a wall), and the angle
from that line to the xy plane, measured perpendicular to the xy plane.  This
is especially useful for the creation of pitched roofs.

Enter the desired angle of the first plane (containing the first line), and
then enter the angle of the second plane (containing the second line).  Pick
three points: the first point is the intersection of the two lines; the second
and third points indicate the other ends of the first and second lines
respectively.

The roof planes are calculated so that they include the two lines, and the
help-line marking the intersection is created.

The order in which the three points are entered is important: if they are
entered counterclockwise the roof will be above the plane defined by the three
indicated points; if the points are entered clockwise, the roof will be
concave, i.e.  underneath that plane.

You are prompted for additional sets of three points until you enter another
command.
