Up: Home page for Qhull
Up: Qhull manual: Table of Contents
To: Programs • Options • Output • Formats • Geomview • Print • Qhull • Precision • Trace
To: synopsis • outputs • examples • notes • options

# rbox -- generate point distributions

> rbox generates random or regular points according to the options given, and outputs the points to stdout. The points are generated in a cube, unless 's', 'x', or 'y' are given.

### »rbox synopsis

    rbox- generate various point distributions.  Default is random in cube.

    args (any order, space separated):
      3000    number of random points in cube, lens, spiral, sphere or grid
      D3      dimension 3-d
      c       add a unit cube to the output ('c G2.0' sets size)
      d       add a unit diamond to the output ('d G2.0' sets size)
      l       generate a regular 3-d spiral
      r       generate a regular polygon, ('r s Z1 G0.1' makes a cone)
      s       generate cospherical points
      x       generate random points in simplex, may use 'r' or 'Wn'
      y       same as 'x', plus simplex
      Pn,m,r  add point [n,m,r] first, pads with 0

      Ln      lens distribution of radius n.  Also 's', 'r', 'G', 'W'.
      Mn,m,r  lattice (Mesh) rotated by [n,-m,0], [m,n,0], [0,0,r], ...
              '27 M1,0,1' is {0,1,2} x {0,1,2} x {0,1,2}.  Try 'M3,4 z'.
      W0.1    random distribution within 0.1 of the cube's or sphere's surface
      Z0.5 s  random points in a 0.5 disk projected to a sphere
      Z0.5 s G0.6 same as Z0.5 within a 0.6 gap

      Bn      bounding box coordinates, default 0.5
      h       output as homogeneous coordinates for cdd
      n       remove command line from the first line of output
      On      offset coordinates by n
      t       use time as the random number seed (default is command line)
      tn      use n as the random number seed
      z       print integer coordinates, default 'Bn' is 1e+06

### »rbox outputs

> The format of the output is the following: first line contains the dimension and a comment, second line contains the number of points, and the following lines contain the points, one point per line. Points are represented by their coordinate values.

> For example, `rbox c 10 D2` generates

> >     2 RBOX c 10 D2
> >     14
> >     -0.4999921736307369 -0.3684622117955817
> >     0.2556053225468894 -0.0413498678629751
> >     0.0327672376602583 -0.2810408135699488
> >     -0.452955383763607 0.17886471718444
> >     0.1792964061529342 0.4346928963760779
> >     -0.1164979223315585 0.01941637230982666
> >     0.3309653464993139 -0.4654278894564396
> >     -0.4465383649305798 0.02970019358182344
> >     0.1711493843897706 -0.4923018137852678
> >     -0.1165843490665633 -0.433157762450313
> >       -0.5   -0.5
> >       -0.5    0.5
> >        0.5   -0.5
> >        0.5    0.5

### »rbox examples

           rbox 10
    	      10 random points in the unit cube centered  at  the
    	      origin.

           rbox 10 s D2
    	      10 random points on a 2-d circle.

           rbox 100 W0
    	      100 random points on the surface of a cube.

           rbox 1000 s D4
    	      1000 random points on a 4-d sphere.

           rbox c D5 O0.5
    	      a 5-d hypercube with one corner at the origin.

           rbox d D10
    	      a 10-d diamond.

           rbox x 1000 r W0
    	      100 random points on the surface of a fixed simplex

           rbox y D12
    	      a 12-d simplex.

           rbox l 10
    	      10 random points along a spiral

           rbox l 10 r
    	      10 regular points  along	a  spiral  plus  two  end
    	      points

           rbox 1000 L10000 D4 s
    	      1000 random points on the surface of a narrow lens.

    	   rbox 1000 L100000 s G1e-6
    		  1000 random points near the edge of a narrow lens

           rbox c G2 d G3
    	      a cube with coordinates +2/-2 and  a  diamond  with
    	      coordinates +3/-3.

           rbox 64 M3,4 z
    	      a  rotated,  {0,1,2,3} x {0,1,2,3} x {0,1,2,3} lat-
    	      tice (Mesh) of integer points.

           rbox P0 P0 P0 P0 P0
    	      5 copies of the origin in 3-d.  Try 'rbox P0 P0  P0
    	      P0 P0 | qhull QJ'.

           r 100 s Z1 G0.1
    	      two  cospherical	100-gons plus another cospherical
    	      point.

           100 s Z1
    	      a cone of points.

           100 s Z1e-7
    	      a narrow cone of points with many precision errors.

### »rbox notes

> Some combinations of arguments generate odd results.

### »rbox options

           n      number of points

           Dn     dimension n-d (default 3-d)

           Bn     bounding box coordinates (default 0.5)

           l      spiral distribution, available only in 3-d

           Ln     lens  distribution  of  radius n.  May be used with
    	      's', 'r', 'G', and 'W'.

           Mn,m,r lattice  (Mesh)  rotated	by  {[n,-m,0],	 [m,n,0],
    	      [0,0,r],	...}.	Use  'Mm,n'  for a rigid rotation
    	      with r = sqrt(n^2+m^2).  'M1,0'  is  an  orthogonal
    	      lattice.	 For  example,	'27  M1,0'  is	{0,1,2} x
    	      {0,1,2} x {0,1,2}.

           s      cospherical points randomly generated in a cube and
    	      projected to the unit sphere

           x      simplicial  distribution.   It  is fixed for option
    	      'r'.  May be used with 'W'.

           y      simplicial distribution plus a simplex.	Both  'x'
    	      and 'y' generate the same points.

           Wn     restrict	points	to distance n of the surface of a
    	      sphere or a cube

           c      add a unit cube to the output

           c Gm   add a cube with all combinations of +m  and  -m  to
    	      the output

           d      add a unit diamond to the output.

           d Gm   add a diamond made of 0, +m and -m to the output

           Pn,m,r add point [n,m,r] to the output first.  Pad coordi-
    	      nates with 0.0.

           n      Remove the command line from the first line of out-
    	      put.

           On     offset the data by adding n to each coordinate.

           t      use  time  in  seconds  as  the  random number seed
    	      (default is command line).

           tn     set the random number seed to n.

           z      generate integer coordinates.  Use 'Bn'  to  change
    	      the  range.   The  default  is 'B1e6' for six-digit
    	      coordinates.  In R^4, seven-digit coordinates  will
    	      overflow hyperplane normalization.

           Zn s   restrict points to a disk about the z+ axis and the
    	      sphere (default Z1.0).  Includes the opposite pole.
    	      'Z1e-6'  generates  degenerate  points under single
    	      precision.

           Zn Gm s
    	      same as Zn with an empty center (default G0.5).

           r s D2 generate a regular polygon

           r s Z1 G0.1
    	      generate a regular cone

Up: Home page for Qhull
Up: Qhull manual: Table of Contents
To: Programs • Options • Output • Formats • Geomview • Print • Qhull • Precision • Trace
To: synopsis • outputs • examples • notes • options

The Geometry Center Home Page

Comments to: qhull@geom.umn.edu
Created: Sept. 25, 1995 --- Last modified: August 12, 1998