121 lines
3 KiB
C++
121 lines
3 KiB
C++
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// convex_hull.cxx -- calculate the convex hull of a set of points
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//
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// Written by Curtis Olson, started September 1998.
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//
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// Copyright (C) 1998 Curtis L. Olson - curt@me.umn.edu
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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//
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// $Id$
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// (Log is kept at end of this file)
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//
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#include <stdio.h>
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#include <list>
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#include <map>
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#ifdef NEEDNAMESPACESTD
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using namespace std;
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#endif
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#include "convex_hull.hxx"
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#include "point2d.hxx"
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// calculate the convex hull of a set of points, return as a list of
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// point2d
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list_container convex_hull( list_container input_list )
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{
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list_iterator current, last;
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map_iterator map_current, map_last;
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// list of translated points
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list_container trans_list;
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// points sorted by radian degrees
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map_container radians_map;
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// will contain the convex hull
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list_container con_hull;
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point2d p, average;
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double sum_x, sum_y;
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int in_count;
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// STEP ONE: Find an average midpoint of the input set of points
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current = input_list.begin();
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last = input_list.end();
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in_count = input_list.size();
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sum_x = sum_y = 0.0;
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while ( current != last ) {
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sum_x += (*current).x;
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sum_y += (*current).y;
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current++;
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}
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average.x = sum_x / in_count;
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average.y = sum_y / in_count;
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printf("Average center point is %.4f %.4f\n", average.x, average.y);
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// STEP TWO: Translate input points so average is at origin
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current = input_list.begin();
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last = input_list.end();
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trans_list.erase( trans_list.begin(), trans_list.end() );
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while ( current != last ) {
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p.x = (*current).x - average.x;
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p.y = (*current).y - average.y;
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printf("p is %.6f %.6f\n", p.x, p.y);
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trans_list.push_back(p);
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current++;
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}
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// STEP THREE: convert to radians and sort by theta
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current = trans_list.begin();
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last = trans_list.end();
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radians_map.erase( radians_map.begin(), radians_map.end() );
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while ( current != last ) {
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p = cart_to_polar_2d(*current);
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radians_map[p.theta] = p.dist;
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current++;
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}
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printf("Sorted list\n");
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map_current = radians_map.begin();
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map_last = radians_map.end();
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while ( map_current != map_last ) {
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p.x = (*map_current).first;
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p.y = (*map_current).second;
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printf("p is %.6f %.6f\n", p.x, p.y);
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map_current++;
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}
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return con_hull;
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}
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// $Log$
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// Revision 1.1 1998/09/04 23:04:51 curt
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// Beginning of convex hull genereration routine.
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//
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//
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