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1.13 The Stack.
GEOMED commands take their arguments from and leave their
results in a push down stack of bodies, faces, edges and vertices.
The contents of the stack are displayed on the left hand side of the
display screen. Every kind of node has a default print identifier,
for the first body created a `B1' is displayed in the stack. Making a
second cube will push a `B2' into the stack. To retrieve `B1' use the
"↑" stack pop command or the "α↑" stack rotate up or "α↓" stack rotate down
or "↔" the swap top of stack command. The "↓" command pushs the stack
down and places in the new top the entity that was previously top of stack.
1.14 The Face, Edge and Vertex Rings.
A polyhedron consists of three circular double linked lists
(called rings); there is a ring of faces, a ring of edges and a ring
of vertices. The head of each ring is the body node. The rings can be
traveled by using the commands "<" and ">" to go forwards and back
through the face ring, the commands "≤" and "≥" for the edge ring, and
the commands "∨" and "∧" for the vertex ring. Notice that when a
face, edge or vertex node is in the top of the stack the
corresponding entity is intensified in the drawing.
1.15 Hidden Line Elimination.
Typing ALT-MODE causes your drawing to be displayed with its
hidden lines eliminated;
as is illustrated by the two pictures of a log cabin in the woods.
To stay in hidden line display mode use the
"_" underbar command; the "β_" returns the display mode default to
display all the lines. The hidden line eliminator, named OCCULT, does
not display concave faces correctly; and for the
sake of speed it does not check for them. The faces of a
polyhedra can be forced convex by applying the "$" command to a body
or to a face.
~X0.60;
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