122 lines
3.1 KiB
Java
122 lines
3.1 KiB
Java
/*
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* Copyright (c) 2017, Adam <Adam@sigterm.info>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
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* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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package net.runelite.api.model;
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import java.util.ArrayList;
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import java.util.List;
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import net.runelite.api.Point;
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/**
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* Implementation of the Jarvis march algorithm
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* https://en.wikipedia.org/wiki/Gift_wrapping_algorithm
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* @author adam
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*/
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public class Jarvis
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{
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/**
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* compute the convex hull of a given set of points
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*
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* @param points
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* @return
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*/
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public static List<Point> convexHull(List<Point> points)
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{
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if (points.size() < 3)
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{
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return null;
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}
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List<Point> ch = new ArrayList<>();
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// find the left most point
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Point left = findLeftMost(points);
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// current point we are on
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Point current = left;
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do
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{
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ch.add(current);
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// the next point - all points are to the right of the
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// line between current and next
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Point next = null;
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for (Point p : points)
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{
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if (next == null)
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{
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next = p;
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continue;
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}
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int cp = crossProduct(current, p, next);
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if (cp > 0 || (cp == 0 && current.distanceTo(p) > current.distanceTo(next)))
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{
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next = p;
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}
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}
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// Points can be null if they are behind or very close to the camera.
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if (next == null)
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{
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return null;
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}
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assert ch.size() <= points.size() : "hull has more points than graph";
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current = next;
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}
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while (current != left);
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return ch;
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}
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private static Point findLeftMost(List<Point> points)
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{
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Point left = null;
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for (Point p : points)
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{
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if (left == null || p.getX() < left.getX())
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{
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left = p;
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}
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else if (p.getX() == left.getX() && p.getY() < left.getY())
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{
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left = p;
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}
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}
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return left;
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}
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private static int crossProduct(Point p, Point q, Point r)
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{
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int val = (q.getY() - p.getY()) * (r.getX() - q.getX())
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- (q.getX() - p.getX()) * (r.getY() - q.getY());
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return val;
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}
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}
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