Dave Hoover
bc7fd397fb
git-svn-id: svn+ssh://src.earth.threerings.net/nenya/trunk@1034 ed5b42cb-e716-0410-a449-f6a68f950b19
100 lines
3.3 KiB
Java
100 lines
3.3 KiB
Java
//
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// $Id$
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//
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// Nenya library - tools for developing networked games
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// Copyright (C) 2002-2010 Three Rings Design, Inc., All Rights Reserved
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// http://code.google.com/p/nenya/
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//
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// This library is free software; you can redistribute it and/or modify it
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// under the terms of the GNU Lesser General Public License as published
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// by the Free Software Foundation; either version 2.1 of the License, or
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// (at your option) any later version.
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//
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// This library 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 GNU
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// Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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package com.threerings.jme.util;
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/**
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* Used to vary a value over time where time is provided at discrete increments
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* (on the frame tick) and the value is computed appropriately. This can be
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* used for fades and other effects where different functions (linear, ease-in
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* ease-out, etc.) should be easy to plug in.
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*/
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public abstract class TimeFunction
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{
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/**
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* Every time function varies a value from some starting value to some
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* ending value over some duration. The way in which it varies
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* (linearly, for example) is up to the derived class.
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*
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* @param start the starting value.
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* @param end the ending value.
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* @param duration the duration in seconds.
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*/
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public TimeFunction (float start, float end, float duration)
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{
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_start = start;
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_end = end;
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_duration = duration;
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}
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/**
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* Returns the current value given the supplied elapsed time. The value
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* will be bounded to the originally supplied starting and ending values at
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* times 0 (and below) and {@link #_duration} (and above) respectively.
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*
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* @param deltaTime the amount of time that has elapsed since the last call
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* to this method.
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*/
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public float getValue (float deltaTime)
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{
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_elapsed += deltaTime;
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if (_elapsed <= 0) {
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return _start;
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} else if (_elapsed >= _duration) {
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return _end;
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} else {
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return computeValue();
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}
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}
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/**
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* Returns true if this function has proceeded the full length of its
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* duration. This should be called after a call to {@link #getValue} has
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* been made to update our internal elapsed time.
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*/
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public boolean isComplete ()
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{
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return _elapsed >= _duration;
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}
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/** Generates a string representation of this instance. */
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public String toString ()
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{
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return _start + " to " + _end + ", " + _elapsed + " of " + _duration;
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}
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/**
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* This must be implemented by our derived class to compute our value given
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* the currently stored {@link #_elapsed} time.
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*/
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protected abstract float computeValue ();
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/** Our starting and ending values. */
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protected float _start, _end;
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/** The number of milliseconds over which we vary our value. */
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protected float _duration;
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/** The number of seconds that have elapsed since we started. */
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protected float _elapsed;
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}
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