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149 lines
4.7 KiB
Java
149 lines
4.7 KiB
Java
// $Id$
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/*
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* WorldEditLibrary
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* Copyright (C) 2010 sk89q <http://www.sk89q.com> and contributors
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*
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* This program 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 3 of the License, or
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* (at your option) any later version.
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*
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* This program 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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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package com.sk89q.worldedit.interpolation;
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import java.util.List;
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import java.util.Map.Entry;
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import java.util.TreeMap;
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import com.sk89q.worldedit.Vector;
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/**
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* Reparametrises another interpolation function by arc length.<br />
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* This is done so entities travel at roughly the same speed across
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* the whole route.
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*
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* @author TomyLobo
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*
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*/
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public class ReparametrisingInterpolation implements Interpolation {
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private final Interpolation baseInterpolation;
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private double totalArcLength;
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private final TreeMap<Double, Double> cache = new TreeMap<Double, Double>();
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public ReparametrisingInterpolation(Interpolation baseInterpolation) {
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this.baseInterpolation = baseInterpolation;
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}
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@Override
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public void setNodes(List<Node> nodes) {
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baseInterpolation.setNodes(nodes);
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cache.clear();
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cache.put(0.0, 0.0);
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cache.put(totalArcLength = baseInterpolation.arcLength(0.0, 1.0), 1.0);
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}
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public Interpolation getBaseInterpolation() {
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return baseInterpolation;
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}
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@Override
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public Vector getPosition(double position) {
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if (position > 1)
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return null;
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return baseInterpolation.getPosition(arcToParameter(position));
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}
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@Override
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public Vector get1stDerivative(double position) {
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if (position > 1)
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return null;
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return baseInterpolation.get1stDerivative(arcToParameter(position)).normalize().multiply(totalArcLength);
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}
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@Override
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public double arcLength(double positionA, double positionB) {
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return baseInterpolation.arcLength(arcToParameter(positionA), arcToParameter(positionB));
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}
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private double arcToParameter(double arc) {
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if (cache.isEmpty())
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throw new IllegalStateException("Must call setNodes first.");
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if (arc > 1) arc = 1;
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arc *= totalArcLength;
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Entry<Double, Double> floorEntry = cache.floorEntry(arc);
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final double leftArc = floorEntry.getKey();
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final double leftParameter = floorEntry.getValue();
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if (leftArc == arc) {
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return leftParameter;
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}
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Entry<Double, Double> ceilingEntry = cache.ceilingEntry(arc);
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if (ceilingEntry == null) {
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System.out.println("Error in arcToParameter: no ceiling entry for "+arc+" found!");
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return 0;
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}
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final double rightArc = ceilingEntry.getKey();
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final double rightParameter = ceilingEntry.getValue();
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if (rightArc == arc) {
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return rightParameter;
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}
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return evaluate(arc, leftArc, leftParameter, rightArc, rightParameter);
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}
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private double evaluate(double arc, double leftArc, double leftParameter, double rightArc, double rightParameter) {
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double midParameter = 0;
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for (int i = 0; i < 10; ++i) {
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midParameter = (leftParameter + rightParameter) * 0.5;
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//final double midArc = leftArc + baseInterpolation.arcLength(leftParameter, midParameter);
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final double midArc = baseInterpolation.arcLength(0, midParameter);
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cache.put(midArc, midParameter);
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if (midArc < leftArc) {
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return leftParameter;
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}
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if (midArc > rightArc) {
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return rightParameter;
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}
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if (Math.abs(midArc - arc) < 0.01) {
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return midParameter;
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}
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if (arc < midArc) {
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// search between left and mid
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rightArc = midArc;
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rightParameter = midParameter;
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}
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else {
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// search between mid and right
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leftArc = midArc;
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leftParameter = midParameter;
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}
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}
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return midParameter;
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}
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@Override
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public int getSegment(double position) {
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if (position > 1)
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return Integer.MAX_VALUE;
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return baseInterpolation.getSegment(arcToParameter(position));
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}
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}
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