DCL:GRPH1:SCPACK: 3-D User Interface
This is a group of subroutines for the tone primitive for a closed triangular area.
In contrast to 2-D, the 3-D tone primitives can only be used to fill triangles.
This is because a tone primitive fills an area in a 2-D plane, and to
perform this in a 3-D space, the 2-D plane must be specified first.
Furthermore, the front or the reverse side may be visible, so 2 types
of tone patterns must be specified. Here, the front side refers to the side
in which the apexes are seen in the counterclockwise direction.
The rest is the same as for 2-D tone primitives.