mirror of https://github.com/ArduPilot/ardupilot
124 lines
4.0 KiB
C++
124 lines
4.0 KiB
C++
/*
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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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* https://wrf.ecse.rpi.edu//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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template <typename T>
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bool Polygon_outside(const Vector2<T> &P, const Vector2<T> *V, unsigned n)
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{
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const bool complete = Polygon_complete(V, n);
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if (complete) {
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// the last point is the same as the first point; treat as if
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// the last point wasn't passed in
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n--;
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}
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unsigned i, j;
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// step through each edge pair-wise looking for crossings:
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bool outside = true;
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for (i=0; i<n; i++) {
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j = i+1;
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if (j >= n) {
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j = 0;
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}
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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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const T dx1 = P.x - V[i].x;
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const T dx2 = V[j].x - V[i].x;
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const T dy1 = P.y - V[i].y;
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const T dy2 = V[j].y - V[i].y;
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const int8_t dx1s = (dx1 < 0) ? -1 : 1;
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const int8_t dx2s = (dx2 < 0) ? -1 : 1;
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const int8_t dy1s = (dy1 < 0) ? -1 : 1;
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const int8_t dy2s = (dy2 < 0) ? -1 : 1;
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const int8_t m1 = dx1s * dy2s;
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const int8_t 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 {
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if (std::is_floating_point<T>::value) {
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if ( dx1 * dy2 > dx2 * dy1 ) {
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outside = !outside;
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}
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} else {
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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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} 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 {
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if (std::is_floating_point<T>::value) {
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if ( dx1 * dy2 < dx2 * dy1 ) {
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outside = !outside;
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}
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} else {
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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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}
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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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template <typename T>
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bool Polygon_complete(const Vector2<T> *V, unsigned n)
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{
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return (n >= 4 && V[n-1] == V[0]);
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}
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// Necessary to avoid linker errors
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template bool Polygon_outside<int32_t>(const Vector2l &P, const Vector2l *V, unsigned n);
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template bool Polygon_complete<int32_t>(const Vector2l *V, unsigned n);
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template bool Polygon_outside<float>(const Vector2f &P, const Vector2f *V, unsigned n);
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template bool Polygon_complete<float>(const Vector2f *V, unsigned n);
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