mirror of https://github.com/ArduPilot/ardupilot
92 lines
2.9 KiB
C++
92 lines
2.9 KiB
C++
/// -*- 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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*
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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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int32_t dx1, dx2, dy1, dy2;
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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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int8_t dx1s, dx2s, dy1s, dy2s, m1, m2;
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#define sign(x) ((x)<0 ? -1 : 1)
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dx1s = sign(dx1);
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dx2s = sign(dx2);
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dy1s = sign(dy1);
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dy2s = sign(dy2);
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m1 = dx1s * dy2s;
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m2 = dx2s * dy1s;
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// we avoid the 64 bit multiplies if we can based on sign checks.
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if (dy2 < 0) {
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if (m1 > m2) {
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outside = !outside;
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} else if (m1 < m2) {
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continue;
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} else if ( dx1 * (int64_t)dy2 > dx2 * (int64_t)dy1 ) {
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outside = !outside;
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}
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} else {
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if (m1 < m2) {
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outside = !outside;
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} else if (m1 > m2) {
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continue;
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} else if ( dx1 * (int64_t)dy2 < dx2 * (int64_t)dy1 ) {
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outside = !outside;
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}
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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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*
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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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