s.sweep(1)		      Grass User's Manual		    s.sweep(1)



NNAAMMEE
       ss..sswweeeepp	-  computes Voronoi diagram or Delaunay triangulation (used by
       s.voronoi and s.delaunay)

SSYYNNOOPPSSIISS
       ss..sswweeeepp [[--ddssttpp]]

DDEESSCCRRIIPPTTIIOONN
       s.sweep reads the standard input for a set  of  points  in  the	 plane
       and   writes   either the Voronoi diagram or the Delaunay triangulation
       to the standard output.	Each input  line   should   consist   of   two
       real  numbers,  separated  by  white  space.   The  program  is used by
       s.voronoi and s.delaunay and is not meant to be useful as a  standalone
       program.   If   option	-t  is	present, the Delaunay triangulation is
       produced.  Each output line is a triple i j k,  which  are the  indices
       of   the  three	points	in  a  Delaunay triangle.  Points are numbered
       starting at 0.  If option -t is not present, the  Voronoi  diagram   is
       produced.  There are four output record types.

	      s a b  indicates	that  an  input point at coordinates a b
		     was seen.

	      l a b c
		     indicates a line with equation ax + by = c.

	      v a b  indicates a vertex at a b.

	      e l v1 v2
		     indicates a Voronoi segment which is  a  subsegment
		     of line number l with endpoints numbered v1 and v2.
		     If v1 or v2 is -1, the line extends to infinity.

       The other options are:

	      s      The input is sorted by  y	coordinate  (the  second
		     number  in  the pair).  The first input line should
		     be npoints xmin xmax ymin ymax.  This describes the
		     number of points and the range of the points.  This
		     line is used to determine internal hash table size;
		     it  need not be exact but performance suffers if it
		     is grossly wrong.

	      p      Produce output suitable  for  input  to  plot  (1),
		     rather than the forms described above.

       On unsorted data uniformly distributed in the unit square, s.sweep uses
       about 20n+140/n bytes of storage.  On sorted data, s.sweep  uses  about
       160/n bytes.

RREEFFEERREENNCCEESS
       Steve  J.  Fortune,  (1987).   A  Sweepline  Algorithm for Voronoi Dia-
       grams, Algorithmica 2, 153-174.

SSEEEE AALLSSOO
       _v_._a_u_t_o_c_o_r_r_, _v_._s_p_a_g_, _v_._s_u_p_p_o_r_t_, _s_._d_e_l_a_u_n_a_y_, _s_._s_w_e_e_p

AAUUTTHHOORR
       James Darrell McCauley,

       GRASS 5 update, improvements: Andrea Aime, Modena, Italy

       _L_a_s_t _c_h_a_n_g_e_d_: _$_D_a_t_e_: _2_0_0_2_/_0_1_/_2_5 _0_5_:_4_5_:_3_5 _$



GRASS 5.0							    s.sweep(1)
