ball_funcs.h

00001 // ball_funcs.h (n-dimensional ball implementation)
00002 //
00003 //  The WorldForge Project
00004 //  Copyright (C) 2000, 2001  The WorldForge Project
00005 //
00006 //  This program is free software; you can redistribute it and/or modify
00007 //  it under the terms of the GNU General Public License as published by
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00009 //  (at your option) any later version.
00010 //
00011 //  This program is distributed in the hope that it will be useful,
00012 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 //  GNU General Public License for more details.
00015 //
00016 //  You should have received a copy of the GNU General Public License
00017 //  along with this program; if not, write to the Free Software
00018 //  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
00019 //
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00021 //  the Worldforge Web Site at http://www.worldforge.org.
00022 //
00023 
00024 // Author: Ron Steinke
00025 
00026 #ifndef WFMATH_BALL_FUNCS_H
00027 #define WFMATH_BALL_FUNCS_H
00028 
00029 #include <wfmath/const.h>
00030 #include <wfmath/point.h>
00031 #include <wfmath/axisbox.h>
00032 #include <wfmath/ball.h>
00033 #include <wfmath/miniball.h>
00034 
00035 namespace WFMath {
00036 
00037 template<const int dim>
00038 inline bool Ball<dim>::isEqualTo(const Ball<dim>& b, double epsilon) const
00039 {
00040   return Equal(m_center, b.m_center, epsilon)
00041       && Equal(m_radius, b.m_radius, epsilon);
00042 }
00043 
00044 template<const int dim>
00045 AxisBox<dim> Ball<dim>::boundingBox() const
00046 {
00047   Point<dim> p_low, p_high;
00048 
00049   for(int i = 0; i < dim; ++i) {
00050     p_low[i] = m_center[i] - m_radius;
00051     p_high[i] = m_center[i] + m_radius;
00052   }
00053 
00054   bool valid = m_center.isValid();
00055 
00056   p_low.setValid(valid);
00057   p_high.setValid(valid);
00058 
00059   return AxisBox<dim>(p_low, p_high, true);
00060 }
00061 
00062 #ifndef WFMATH_NO_TEMPLATES_AS_TEMPLATE_PARAMETERS
00063 template<const int dim, template<class, class> class container>
00064 Ball<dim> BoundingSphere(const container<Point<dim>, std::allocator<Point<dim> > >& c)
00065 {
00066   _miniball::Miniball<dim> m;
00067   _miniball::Wrapped_array<dim> w;
00068 
00069   typename container<Point<dim>, std::allocator<Point<dim> > >::const_iterator i, end = c.end();
00070   bool valid = true;
00071 
00072   for(i = c.begin(); i != end; ++i) {
00073     valid = valid && i->isValid();
00074     for(int j = 0; j < dim; ++j)
00075       w[j] = (*i)[j];
00076     m.check_in(w);
00077   }
00078 
00079   m.build();
00080 
00081 #ifndef NDEBUG
00082   double dummy;
00083 #endif
00084   assert("Check that bounding sphere is good to library accuracy" &&
00085          m.accuracy(dummy) < WFMATH_EPSILON);
00086 
00087   w = m.center();
00088   Point<dim> center;
00089 
00090   for(int j = 0; j < dim; ++j)
00091     center[j] = w[j];
00092 
00093   center.setValid(valid);
00094 
00095   return Ball<dim>(center, sqrt(m.squared_radius()));
00096 }
00097 
00098 template<const int dim, template<class, class> class container>
00099 Ball<dim> BoundingSphereSloppy(const container<Point<dim>, std::allocator<Point<dim> > >& c)
00100 {
00101   // This is based on the algorithm given by Jack Ritter
00102   // in Volume 2, Number 4 of Ray Tracing News
00103   // <http://www.acm.org/tog/resources/RTNews/html/rtnews7b.html>
00104 
00105   typename container<Point<dim>, std::allocator<Point<dim> > >::const_iterator i = c.begin(),
00106                                                 end = c.end();
00107   assert(i != end);
00108 
00109   CoordType min[dim], max[dim];
00110   typename container<Point<dim>, std::allocator<Point<dim> > >::const_iterator min_p[dim], max_p[dim];
00111   bool valid = i->isValid();
00112 
00113   for(int j = 0; j < dim; ++j) {
00114     min[j] = max[j] = (*i)[j];
00115     min_p[j] = max_p[j] = i;
00116   }
00117 
00118   while(++i != end) {
00119     valid = valid && i->isValid();
00120     for(int j = 0; j < dim; ++j) {
00121       if(min[j] > (*i)[j]) {
00122         min[j] = (*i)[j];
00123         min_p[j] = i;
00124       }
00125       if(max[j] < (*i)[j]) {
00126         max[j] = (*i)[j];
00127         max_p[j] = i;
00128       }
00129     }
00130   }
00131 
00132   CoordType span = -1;
00133   int direction = -1;
00134 
00135   for(int j = 0; j < dim; ++j) {
00136     CoordType new_span = max[j] - min[j];
00137     if(new_span > span) {
00138       span = new_span;
00139       direction = j;
00140     }
00141   }
00142 
00143   assert("Have a direction of maximum size" && direction != -1);
00144 
00145   Point<dim> center = Midpoint(*(min_p[direction]), *(max_p[direction]));
00146   CoordType dist = SloppyDistance(*(min_p[direction]), center);
00147 
00148   for(i = c.begin(); i != end; ++i) {
00149     if(i == min_p[direction] || i == max_p[direction])
00150       continue; // We already have these
00151 
00152     CoordType new_dist = SloppyDistance(*i, center);
00153 
00154     if(new_dist > dist) {
00155       CoordType delta_dist = (new_dist - dist) / 2;
00156       // Even though new_dist may be too large, delta_dist / new_dist
00157       // always gives enough of a shift to include the new point.
00158       center += (*i - center) * delta_dist / new_dist;
00159       dist += delta_dist;
00160       assert("Shifted ball contains new point" &&
00161              SquaredDistance(*i, center) <= dist * dist);
00162     }
00163   }
00164 
00165   center.setValid(valid);
00166 
00167   return Ball<2>(center, dist);
00168 }
00169 #endif
00170 
00171 // These two are here, instead of defined in the class, to
00172 // avoid include order problems
00173 
00174 template<const int dim>
00175 inline Ball<dim> Point<dim>::boundingSphere() const
00176 {
00177   return Ball<dim>(*this, 0);
00178 }
00179 
00180 template<const int dim>
00181 inline Ball<dim> Point<dim>::boundingSphereSloppy() const
00182 {
00183   return Ball<dim>(*this, 0);
00184 }
00185 
00186 } // namespace WFMath
00187 
00188 #endif  // WFMATH_BALL_FUNCS_H

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