65 lines
1.8 KiB
C++
65 lines
1.8 KiB
C++
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/*
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----
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This file is part of SECONDO.
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Copyright (C) 2014,
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Faculty of Mathematics and Computer Science,
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Database Systems for New Applications.
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SECONDO 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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SECONDO 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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You should have received a copy of the GNU General Public License
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along with SECONDO; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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----
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*/
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#include <PrecTools.h>
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#include <vector>
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#include <PrecisePoint.h>
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namespace precisetools{
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bool isClockwise(std::vector<MPrecPoint>& cycle){
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assert(cycle.size()>3);
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int smallestIndex = 0;
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for(size_t i=1;i<cycle.size();i++){
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if(cycle[i] < cycle[smallestIndex]){
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smallestIndex = 0;
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}
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}
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int previous = (smallestIndex + (cycle.size()-1)) % cycle.size();
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int next = (smallestIndex + 1) % cycle.size();
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MPrecPoint p1 = cycle[previous];
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MPrecPoint p2 = cycle[smallestIndex];
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MPrecPoint p3 = cycle[next];
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if(p1.getX()==p2.getX()){ // found vertical line
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return p2.getY() > p1.getY(); // up
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}
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if(p2.getX() == p3.getX()){
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return p2.getY() < p3.getY();
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}
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// no vertical line, compare slopes
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MPrecCoordinate s12 = (p1.getY() - p2.getY()) / (p1.getX() - p2.getX());
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MPrecCoordinate s32 = (p3.getY() - p2.getY()) / (p3.getX() - p2.getX());
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return s12 < s32;
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}
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} // end of namespace precisetools
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