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NAME
     pointlist - library for getting  and  setting  the	 list  of
     points in an OOGL object.

SYNOPSIS
     #include "pointlist.h"

     void pointlist_init();

     HPoint3 *PointList_get( Geom *geom, Transform T, int CoordSystem );
     HPoint3 *PointList_fillin(	Geom *geom, Transform T, int CoordSystem,
	  HPoint3 *plist );
     void PointList_set( Geom *geom, int CoordSystem, HPoint3 *plist );
     int PointList_length( Geom	*geom );

DESCRIPTION
     The pointlist library contains several routines for  getting
     and  setting  the list of points in a Geomview object.  This
     is	useful for performings operations which	operate	solely on
     the  points  of  an  object,  for	example, transforming the
     entire object by transforming its points.	 pointlist_init()
     must be called prior to calling any of the	other routines.

     The value CoordSystem is the coordinate system in which  the
     coordinates  are  specified.   It	may  be	set to one of two
     values  declared	in   pointlist.h:    POINTLIST_SELF   and
     POINTLIST_PRIMITIVE.    POINTLIST_SELF  indicates	that  the
     coordinates will be in the	coordinate system  of  the  given
     Geom.   POINTLIST_PRIMITIVE  indicates  that the coordinates
     will be in	the coordinate system of  the  lowest-level  OOGL
     primitive.	  These	 specifications	are analogous to the key-
     words  "self"  and	 "primitive"  in  the  Geomview	  command
     language  (See  geomview(5)).  The	discerning user	will note
     that these	coordinate  systems  will  only	 cause	different
     results if	the geom is an inst or a list containing an inst.
     The not-so-discerning user	needn't	worry about it.

     PointList_get() and  PointList_fillin()  have  very  similar
     functions.	  PointList_get()  takes  a  geom  and	returns	a
     pointer to	an allocated array of  HPoint3's  containing  the
     points  of	 the  object  in the specified coordinate system.
     PointList_fillin()	puts the points	of the geom in the  array
     plist and returns plist.

     The arguement T is	used internally	by  the	 routines  (since
     they  are	recursive).   Passing  in anything other than the
     identity matrix is	very very unwise and will (at best) prob-
     ably produce unexpected results.

     The only slightly special case is that of an inst containing
     more than one appearance of the base geom.	 In the	inst data
     strucutre,	there is actually only one list	of points for the
     base  geom	 no  matter  how  many times it	is instanced.  In
     spite of this, the	routines will return  a	 list  of  points
     which  contains  the  points of the base geom instanced once
     for each transform	in the inst.  For example, a inst  object
     whose  base geom is a cube	and which contains two transforms
     will return a point list sixteen points long, since  a  cube
     has eight points.

     PointList_set() is	used to	set the	points to a geom to those
     contained	in  plist.   In	 general,  plist will be an array
     returned by PointList_get and  somehow  transformed  by  the
     calling program. The only slightly	mysterious aspect of this
     routine is	its handling of	inst objects with more	than  one
     appearance	of the base geom.  In this case, the first set of
     points in the plist is used to redefine the  points  of  the
     base geom.	 The rest of plist is ignored.

     PointList_length()	returns	the total number of points  in	a
     geom,   which  is	the  length  of	 the  array  returned  by
     PointList_get() and the length of the plist arrays	that must
     be	passed to PointList_fillin() and PointList_set().

LINKING
     To	link your program with the pointlist library, you  should
     specify  -lpointlist  followed  by	 the  usual  list of OOGL
     libraries,	as in
     cc	-L${LIBDIR} prog.c -lpointlist ${ALLOOGLLIBS}

SEE ALSO
     geomview(5)

AUTHOR
     Celeste Fowler	      email:  [email protected]
     The Geometry Center      phone:  (612) 626-8304
     1300 South	Second Street
     Minneapolis, MN  55454

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