perm filename PAGE14[00,BGB] blob sn#046246 filedate 1973-06-05 generic text, type T, neo UTF8
~F83. POLYGON NODE FORMAT.

	_____________________________________________ 
	word |        CW         |        CCW        |
	  0  |             polygon ring              | 3
	_____|___________________|___________________|
	word |        DAD        |        SON        |
	  1  |       level       |     1st vector    | 3
	_____|___________________|___________________|
	word |       type        |       reloc       |
	  2  |        10         |      33 3233      |
	_____|___________________|___________________|
	word |       ENDO        |        EXO        |
	  3  |1st polygon within |polygon surround me| 3
	_____|___________________|___________________|
	word |       ALT         |       ncnt        |
	  4  | shape {or 1st arc}|  number of sides  | 2
	_____|___________________|___________________|
	word |       NGON        |       PGON        |
	  5  | nest bro polygon  | nest sis polygon  | 3
	_____|___________________|___________________|
	word |                   |                   |
	  6  |       NTIME   time line   PTIME       | 3
	_____|___________________|___________________|

	Every polygon belongs to a level pointed  at by the DAD link;
the ring  of polygons of a  level is formed in the  CW and CCW links;
the son of a  polygon is its first vector  (or arc after the  polygon
has been  smoothed) and  that first  vector has  the upper  left most
locus of any vector of the polygon.

	The  ENDO,   EXO,  NGON,   PGON are  used to  form the nested
polygon tree.   Every polygon  has non-NIL NGON  and PGON links;  the
trivial  case being that  the polygon  points at itself  twice. Every
polygon except one,  the outer  border polygon,   has  a non-NIL  EXO
link.  Every polygon that surrounds one or  more other polygons has a
non-NIL ENDO link.

	The ALT link  position of a polygon temporarily points to the
first arc  of a  polygon during  smoothing when  a  polygon has  both
vectors and arcs. The final contents of  the ALT link is a pointer to
the  shape node of the  polygon. The ncnt  datum indicates the number
of sides of the polygon.
	
	The time  line  of polygons  runs thru  the  NTIME and  PTIME
links which point either  to a nearly exact match of a polygon; or to
a fusion  polygon of  a two  for  one match;  or to  one of  the  two
fission parts  of a  one for  two match; (to  find the  other fission
part, the time links of the vectors must be scanned).
~I1973,800;F8- 14 -