Hull 1.0:
This program computes convex hulls, Delaunay triangulations, alpha shapes,
and Voronoi volumes, using an incremental algorithm and exact arithmetic.

To install, type "make", possibly after adjusting the Makefile.

Author:
Ken Clarkson,
clarkson@research.bell-labs.com,
http://cm.bell-labs.com/who/clarkson.

https://netlib.sandia.gov/voronoi/hull.html

Ken Clarkson先生的版本，在windows中编译时会出现一些错误，我改正了这些错误，使本程序可以在windows版本的CodeBlocks中编译。

这个程序对点的数量有限制：
原始文件中都是10000
所以当点数超过1万时，会出错。

hull.h
#define MAXPOINTS 10000

pointsites.h
#define MAXBLOCKS 10000



##Synopsis

hull -d -f<format> -A -aa<alpha> -af<format> -oN -ov -s<seed> -r -m<multiplier> -X<debug_file> -i<input_file> -oF<output_file>
Description
The input_file (default stdin) is a sequence of points (also called sites), separated by \n; a d-dimensional point is specified as a group of d floats separated by whitespace (other than \n).
The output_file (default stdout) gives d-tuples of the input points, where a point is given as an integer i if it was the i'th point in the input_file. If the convex hull lies in a flat (affine subspace) of dimension d', the output will comprise a list of d'-tuples, the vertices of the convex hull relative to that flat.

The output tuples represent the facets of the convex hull of the input set. A facet which is not a simplex is output implicitly as the collection of simplices of its triangulation.

The output for Delaunay triangulation includes a "point at infinity", numbered -1; facets including it correspond to facets of the convex hull of the sites.

Some chatter will appear on debug_file (default stderr).

The coordinates of the input points are rounded to integers. With -m<multiplier>, the coordinates are multiplied by multiplier before this rounding.

The program attempts to use a method that gives exact answers to numerical tests; in some circumstances, this may fail, and with some warnings, the program continues, using approximate arithmetic.

##More detail on the options:

-d
compute the Delaunay triangulation of the input set.
-f<format>
give the main output (convex hull or Delaunay triangulation) in output <format>, which is by default the list of vertex numbers described above, or ps, for postscript output of planar points, or off, for OFF output of 3d points.
-aa<alpha>
compute the alpha shape using parameter < alpha >: the output is the set of all d-tuples of sites such that there is a ball of radius < alpha > containing those sites on its bounding sphere, and containing no other sites. A Delaunay triangulation computation is implied by this option and by -A.
-af<format>
output the alpha shape in format <format>, as in option -f.
-A
compute the alpha shape of the input, finding the smallest alpha so that the sites are all contained in the alpha-shape.
-r
randomly shuffle the input points; this may speed up the program.
-s<seed>
randomly shuffle using < seed > for the random number generator.
-oN
do not produce main output (convex hull or Delaunay triangulation). If you want an alpha shape only, you need this to turn off the Delaunay output.
-ov
Give volumes of Voronoi regions of input sites, and in general d'-volumes of d'-dimensional Voronoi cells. Implies -d.
Bugs/Portability
If the convex hull is a single point, the algorithm will fail to report it. All other degeneracies should be handled. Tie-breaking is done so that all reported facets are simplices. If the input points are degenerate, some hull facets may be; for example, some Delaunay simplices may have zero volume. Determining non-simplicial facets or deleting zero-volume Delaunauy simplices could be done in post-processing (not implemented).
The file rand.c includes calls to pseudo-random number generators;

No simplices are deleted; the only way to free storage is to free it all using free_hull_storage.

##Author
Ken Clarkson, (clarkson@research.bell-labs.com),
using an earlier version written by Susan Dorward, who is not to blame.