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/*
* crop_algorithms.h -- clipping/cropping templates
*
* This file is part of ePiX, a C++ library for creating high-quality
* figures in LaTeX
*
* Version 1.1.9
* Last Change: July 31, 2007
*/
/*
* Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007
* Andrew D. Hwang <rot 13 nujnat at zngupf dot ubylpebff dot rqh>
* Department of Mathematics and Computer Science
* College of the Holy Cross
* Worcester, MA, 01610-2395, USA
*/
/*
* ePiX is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* ePiX is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
* License for more details.
*
* You should have received a copy of the GNU General Public License
* along with ePiX; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* This file defines list<edge> manipulating template functions and
* associated utilities. Each chop function returns a reference to its
* list<edge> argument.
*
* double height(perp, base, arg)
* PT cut_location(perp, base, tail, head)
* cull(edges) // remove edges whose tail and head are equal
* loopify(edges) // replace contiguous unseen edges with one seen edge
* chop_path(perp, base, edges) // cull to a halfspace/halfplane
* chop_loop(perp, base, edges) // same, for loops
*/
#ifndef EPIX_CROP_ALGO
#define EPIX_CROP_ALGO
#include <list>
#include "constants.h"
namespace ePiX {
// perp assumed to be *unit*
template <typename PT>
double height(const PT& perp, const PT& base, const PT& arg)
{
// return (perp|(operator-(arg, base)));
return (perp|(arg - base));
}
// no check for parallel
template <typename PT>
PT cut_location(const PT& perp, const PT& base, const PT& p1, const PT& p2)
{
// PT dir(operator-(p2, p1)); // -dir to base
// return p1 + (((operator-(base, p1))|perp)/(dir|perp))*dir;
PT dir(p2 - p1); // -dir to base
return p1 + (((base - p1)|perp)/(dir|perp))*dir;
}
// remove edges whose tail, head are equal
template <typename PT>
std::list<edge_data<PT> >& cull(std::list<edge_data<PT> >& edges)
{
typename std::list<edge_data<PT> >::iterator ep(edges.begin());
while (ep != edges.end())
{
if ((*ep).is_null())
ep = edges.erase(ep);
else
++ep;
}
return edges;
}
template <typename PT>
std::list<edge_data<PT> >& loopify(std::list<edge_data<PT> >& edges)
{
if (edges.begin() == edges.end())
return edges;
typename std::list<edge_data<PT> >::iterator ep(edges.begin());
bool in_path(false); // currently in a visible sublist?
// After first pass, ep points to first visible edge
while (ep != edges.end())
{
if (!(*ep).is_seen()) // invisible edge
{
ep=edges.erase(ep);
in_path=false;
continue;
}
// else visible edge
if (in_path)
{
++ep;
continue;
}
// else
in_path=true;
if (ep != edges.begin()) // join our tail to previous head
{
typename std::list<edge_data<PT> >::iterator prev(ep);
--prev;
ep = edges.insert(ep, edge_data<PT>((*prev).head(),
(*ep).tail(),
true));
++ep;
++ep;
}
}
// all edges examined; if we contain multiple edges, close final cut
ep = edges.begin();
// contains at most one edge
if (ep == edges.end())
; // return below
else if (++ep == edges.end())
edges.erase(edges.begin());
else
{
ep = edges.end();
--ep;
edges.push_back(edge_data<PT>((*ep).head(),
(*edges.begin()).tail(),
true));
}
return edges;
} // end of loopify()
// return result of clipping edges to half space/plane through base
// with unit inward normal perp
template <typename PT>
std::list<edge_data<PT> >& chop_path(const PT& perp, const PT& base,
std::list<edge_data<PT> >& edges)
{
typename std::list<edge_data<PT> >::iterator ep(edges.begin());
while(ep != edges.end())
{
if (!(*ep).is_seen())
{
++ep;
continue;
}
// else
const PT tail((*ep).tail());
const PT head((*ep).head());
const double ht_tail(height(perp, base, tail));
const double ht_head(height(perp, base, head));
// non-crossings:
// unclipped
if (-EPIX_EPSILON < ht_tail && -EPIX_EPSILON < ht_head)
{
++ep;
continue;
}
// clipped
else if (ht_tail <= 0 && ht_head <= 0)
{
(*ep).seen(false);
++ep;
continue;
}
// else one end below -EPS, one above 0; split edge
const PT crossing(cut_location(perp, base, tail, head));
// visibility of segments
bool vis_tail(false), vis_head(true);
if (0 < ht_tail)
{
vis_tail=true;
vis_head=false;
}
ep = edges.erase(ep);
ep=edges.insert(ep, edge_data<PT>(crossing, head, vis_head));
ep=edges.insert(ep, edge_data<PT>(tail, crossing, vis_tail));
++ep;
++ep;
} // all edges examined
return cull(edges);
} // end of chop_path()
template <typename PT>
std::list<edge_data<PT> >& chop_loop(const PT& perp, const PT& base,
std::list<edge_data<PT> >& edges)
{
return loopify(chop_path(perp, base, edges));
}
} // end of namespace
#endif /* EPIX_CROP_ALGO */
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