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70 lines
2.2 KiB
70 lines
2.2 KiB
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- |
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/* |
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* polygon.cpp |
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* Copyright (C) Andrew Tridgell 2011 |
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* |
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* This file is free software: you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License as published by the |
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* Free Software Foundation, either version 3 of the License, or |
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* (at your option) any later version. |
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* |
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* This file is distributed in the hope that it will be useful, but |
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* WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. |
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* See the 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 along |
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* with this program. If not, see <http://www.gnu.org/licenses/>. |
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*/ |
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#include "AP_Math.h" |
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/* |
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The point in polygon algorithm is based on: |
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http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html |
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*/ |
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/* |
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Polygon_outside(): test for a point in a polygon |
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Input: P = a point, |
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V[] = vertex points of a polygon V[n+1] with V[n]=V[0] |
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Return: true if P is outside the polygon |
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This does not take account of the curvature of the earth, but we |
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expect that to be very small over the distances involved in the |
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fence boundary |
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*/ |
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bool Polygon_outside(const Vector2l &P, const Vector2l *V, unsigned n) |
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{ |
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unsigned i, j; |
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bool outside = true; |
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for (i = 0, j = n-1; i < n; j = i++) { |
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if ((V[i].y > P.y) == (V[j].y > P.y)) { |
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continue; |
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} |
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float dx1, dx2, dy1, dy2; |
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// we convert the deltas to floating point numbers to |
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// prevent integer overflow while maintaining maximum precision |
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dx1 = P.x - V[i].x; |
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dx2 = V[j].x - V[i].x; |
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dy1 = P.y - V[i].y; |
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dy2 = V[j].y - V[i].y; |
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if ( dx1 < dx2 * dy1 / dy2 ) { |
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outside = !outside; |
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} |
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} |
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return outside; |
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} |
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/* |
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check if a polygon is complete. |
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We consider a polygon to be complete if we have at least 4 points, |
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and the first point is the same as the last point. That is the |
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minimum requirement for the Polygon_outside function to work |
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*/ |
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bool Polygon_complete(const Vector2l *V, unsigned n) |
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{ |
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return (n >= 4 && V[n-1].x == V[0].x && V[n-1].y == V[0].y); |
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}
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