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user_eg.c
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/*<html><pre> -<a href="../libqhull/qh-user.htm"
>-------------------------------</a><a name="TOP">-</a>
user_eg.c
sample code for calling qhull() from an application
call with:
user_eg "cube/diamond options" "delaunay options" "halfspace options"
for example:
user_eg # return summaries
user_eg "n" "o" "Fp" # return normals, OFF, points
user_eg "n Qt" "o" "Fp" # triangulated cube
user_eg "QR0 p" "QR0 v p" "QR0 Fp" # rotate input and return points
# 'v' returns Voronoi
# transform is rotated for halfspaces
main() makes three runs of qhull.
1) compute the convex hull of a cube
2a) compute the Delaunay triangulation of random points
2b) find the Delaunay triangle closest to a point.
3) compute the halfspace intersection of a diamond
notes:
For another example, see main() in unix.c and user_eg2.c.
These examples, call qh_qhull() directly. They allow
tighter control on the code loaded with Qhull.
For a C++ example, see user_eg3/user_eg3_r.cpp
Summaries are sent to stderr if other output formats are used
compiled by 'make bin/user_eg'
see libqhull.h for data structures, macros, and user-callable functions.
*/
#define qh_QHimport
#include "libqhull/qhull_a.h"
/*-------------------------------------------------
-internal function prototypes
*/
void print_summary(void);
void makecube(coordT *points, int numpoints, int dim);
void makeDelaunay(coordT *points, int numpoints, int dim, int seed);
void findDelaunay(int dim);
void makehalf(coordT *points, int numpoints, int dim);
/*-------------------------------------------------
-print_summary()
*/
void print_summary(void) {
facetT *facet;
int k;
printf("\n%d vertices and %d facets with normals:\n",
qh num_vertices, qh num_facets);
FORALLfacets {
for (k=0; k < qh hull_dim; k++)
printf("%6.2g ", facet->normal[k]);
printf("\n");
}
}
/*--------------------------------------------------
-makecube- set points to vertices of cube
points is numpoints X dim
*/
void makecube(coordT *points, int numpoints, int dim) {
int j,k;
coordT *point;
for (j=0; j<numpoints; j++) {
point= points + j*dim;
for (k=dim; k--; ) {
if (j & ( 1 << k))
point[k]= 1.0;
else
point[k]= -1.0;
}
}
} /*.makecube.*/
/*--------------------------------------------------
-makeDelaunay- set points for dim Delaunay triangulation of random points
points is numpoints X dim.
notes:
makeDelaunay() in user_eg2.c uses qh_setdelaunay() to project points in place.
*/
void makeDelaunay(coordT *points, int numpoints, int dim, int seed) {
int j,k;
coordT *point, realr;
printf("seed: %d\n", seed);
qh_RANDOMseed_( seed);
for (j=0; j<numpoints; j++) {
point= points + j*dim;
for (k= 0; k < dim; k++) {
realr= qh_RANDOMint;
point[k]= 2.0 * realr/(qh_RANDOMmax+1) - 1.0;
}
}
} /*.makeDelaunay.*/
/*--------------------------------------------------
-findDelaunay- find Delaunay triangle for [0.5,0.5,...]
assumes dim < 100
notes:
calls qh_setdelaunay() to project the point to a parabaloid
warning:
This is not implemented for tricoplanar facets ('Qt'),
See <a href="../html/qh-code.htm#findfacet">locate a facet with qh_findbestfacet()</a>
*/
void findDelaunay(int dim) {
int k;
coordT point[ 100];
boolT isoutside;
realT bestdist;
facetT *facet;
vertexT *vertex, **vertexp;
for (k= 0; k < dim; k++)
point[k]= 0.5;
qh_setdelaunay(dim+1, 1, point);
facet= qh_findbestfacet(point, qh_ALL, &bestdist, &isoutside);
if (facet->tricoplanar) {
fprintf(stderr, "findDelaunay: not implemented for triangulated, non-simplicial Delaunay regions (tricoplanar facet, f%d).\n",
facet->id);
qh_errexit(qh_ERRqhull, facet, NULL);
}
FOREACHvertex_(facet->vertices) {
for (k=0; k < dim; k++)
printf("%5.2f ", vertex->point[k]);
printf("\n");
}
} /*.findDelaunay.*/
/*--------------------------------------------------
-makehalf- set points to halfspaces for a (dim)-dimensional diamond
points is numpoints X dim+1
each halfspace consists of dim coefficients followed by an offset
*/
void makehalf(coordT *points, int numpoints, int dim) {
int j,k;
coordT *point;
for (j=0; j<numpoints; j++) {
point= points + j*(dim+1);
point[dim]= -1.0; /* offset */
for (k=dim; k--; ) {
if (j & ( 1 << k))
point[k]= 1.0;
else
point[k]= -1.0;
}
}
} /*.makehalf.*/
#define DIM 3 /* dimension of points, must be < 31 for SIZEcube */
#define SIZEcube (1<<DIM)
#define SIZEdiamond (2*DIM)
#define TOTpoints (SIZEcube + SIZEdiamond)
/*--------------------------------------------------
-main- derived from Qhull-template in user.c
see program header
this contains three runs of Qhull for convex hull, Delaunay
triangulation or Voronoi vertices, and halfspace intersection
*/
int main(int argc, char *argv[]) {
int dim= DIM; /* dimension of points */
int numpoints; /* number of points */
coordT points[(DIM+1)*TOTpoints]; /* array of coordinates for each point */
coordT *rows[TOTpoints];
boolT ismalloc= False; /* True if qhull should free points in qh_freeqhull() or reallocation */
char flags[250]; /* option flags for qhull, see qh-quick.htm */
FILE *outfile= stdout; /* output from qh_produce_output()
use NULL to skip qh_produce_output() */
FILE *errfile= stderr; /* error messages from qhull code */
int exitcode; /* 0 if no error from qhull */
facetT *facet; /* set by FORALLfacets */
int curlong, totlong; /* memory remaining after qh_memfreeshort */
int i;
QHULL_LIB_CHECK
printf("This is the output from user_eg.c\n\n\
It shows how qhull() may be called from an application using the qhull\n\
shared library. user_eg is not part of qhull itself. If it appears\n\
accidently, please remove user_eg.c from your project. If it fails\n\
immediately, user_eg.c was incorrectly linked to the reentrant library.\n\
Also try 'user_eg T1 2>&1'\n\n");
#if qh_QHpointer /* see user.h */
if (qh_qh){
printf("QH6233: Qhull link error. The global variable qh_qh was not initialized\n\
to NULL by global.c. Please compile user_eg.c with -Dqh_QHpointer_dllimport\n\
as well as -Dqh_QHpointer, or use libqhullstatic, or use a different tool chain.\n\n");
return -1;
}
#endif
/*
Run 1: convex hull
*/
printf( "\ncompute convex hull of cube after rotating input\n");
sprintf(flags, "qhull s Tcv %s", argc >= 2 ? argv[1] : "");
numpoints= SIZEcube;
makecube(points, numpoints, DIM);
for (i=numpoints; i--; )
rows[i]= points+dim*i;
qh_printmatrix(outfile, "input", rows, numpoints, dim);
exitcode= qh_new_qhull(dim, numpoints, points, ismalloc,
flags, outfile, errfile);
if (!exitcode) { /* if no error */
/* 'qh facet_list' contains the convex hull */
print_summary();
FORALLfacets {
/* ... your code ... */
}
}
qh_freeqhull(!qh_ALL); /* free long memory */
qh_memfreeshort(&curlong, &totlong); /* free short memory and memory allocator */
if (curlong || totlong)
fprintf(errfile, "qhull internal warning (user_eg, #1): did not free %d bytes of long memory (%d pieces)\n", totlong, curlong);
/*
Run 2: Delaunay triangulation
*/
printf( "\ncompute %d-d Delaunay triangulation\n", dim);
sprintf(flags, "qhull s d Tcv %s", argc >= 3 ? argv[2] : "");
numpoints= SIZEcube;
makeDelaunay(points, numpoints, dim, (int)time(NULL));
for (i=numpoints; i--; )
rows[i]= points+dim*i;
qh_printmatrix(outfile, "input", rows, numpoints, dim);
exitcode= qh_new_qhull(dim, numpoints, points, ismalloc,
flags, outfile, errfile);
if (!exitcode) { /* if no error */
/* 'qh facet_list' contains the convex hull */
/* If you want a Voronoi diagram ('v') and do not request output (i.e., outfile=NULL),
call qh_setvoronoi_all() after qh_new_qhull(). */
print_summary();
FORALLfacets {
/* ... your code ... */
}
printf( "\nfind %d-d Delaunay triangle closest to [0.5, 0.5, ...]\n", dim);
exitcode= setjmp(qh errexit);
if (!exitcode) {
/* Trap Qhull errors in findDelaunay(). Without the setjmp(), Qhull
will exit() after reporting an error */
qh NOerrexit= False;
findDelaunay(DIM);
}
qh NOerrexit= True;
}
#if qh_QHpointer /* see user.h */
{
qhT *oldqhA, *oldqhB;
coordT pointsB[DIM*TOTpoints]; /* array of coordinates for each point */
printf( "\nsave first triangulation and compute a new triangulation\n");
oldqhA= qh_save_qhull();
sprintf(flags, "qhull s d Tcv %s", argc >= 3 ? argv[2] : "");
numpoints= SIZEcube;
makeDelaunay(pointsB, numpoints, dim, (int)time(NULL)+1);
for (i=numpoints; i--; )
rows[i]= pointsB+dim*i;
qh_printmatrix(outfile, "input", rows, numpoints, dim);
exitcode= qh_new_qhull(dim, numpoints, pointsB, ismalloc,
flags, outfile, errfile);
if (!exitcode)
print_summary();
printf( "\nsave second triangulation and restore first one\n");
oldqhB= qh_save_qhull();
qh_restore_qhull(&oldqhA);
print_summary();
printf( "\nfree first triangulation and restore second one.\n");
qh_freeqhull(qh_ALL); /* free short and long memory used by first call */
/* do not use qh_memfreeshort */
qh_restore_qhull(&oldqhB);
print_summary();
}
#endif
qh_freeqhull(!qh_ALL); /* free long memory */
qh_memfreeshort(&curlong, &totlong); /* free short memory and memory allocator */
if (curlong || totlong)
fprintf(errfile, "qhull internal warning (user_eg, #2): did not free %d bytes of long memory (%d pieces)\n", totlong, curlong);
/*
Run 3: halfspace intersection about the origin
*/
printf( "\ncompute halfspace intersection about the origin for a diamond\n");
sprintf(flags, "qhull H0 s Tcv %s", argc >= 4 ? argv[3] : "Fp");
numpoints= SIZEcube;
makehalf(points, numpoints, dim);
for (i=numpoints; i--; )
rows[i]= points+(dim+1)*i;
qh_printmatrix(outfile, "input as halfspace coefficients + offsets", rows, numpoints, dim+1);
/* use qh_sethalfspace_all to transform the halfspaces yourself.
If so, set 'qh feasible_point and do not use option 'Hn,...' [it would retransform the halfspaces]
*/
exitcode= qh_new_qhull(dim+1, numpoints, points, ismalloc,
flags, outfile, errfile);
if (!exitcode)
print_summary();
qh_freeqhull(!qh_ALL);
qh_memfreeshort(&curlong, &totlong);
if (curlong || totlong) /* could also check previous runs */
fprintf(stderr, "qhull internal warning (user_eg, #3): did not free %d bytes of long memory (%d pieces)\n",
totlong, curlong);
return exitcode;
} /* main */

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