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Java class that performs a fixed rate simulation.
/*
* Copyright (c) 2012 Michael Nischt
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* Neither the name of the project's author nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
/**
* Class that performs a fixed rate simulation.
*
* @author Michael Nischt
*/
public final class Simulation {
/**
* Callback interface which is called once for every simulation step at the specified intervall
*/
public interface Updater {
void update(double dT);
}
private static final double SIM_RATE = 1.0/60.0;
private final Updater updater;
private final double stepDuration;
private long lastTime;
private double remainingTime;
/**
* Creates a new simulation routine which calls the updater with a frequency of 60Hz.
* @param updater the simulation callback interface
*/
public Simulation(Updater updater) {
this(updater, SIM_RATE);
}
/**
* Creates a new simulation routine which calls the updater with a frequency of 60Hz.
* @param updater the simulation callback interface
* @param stepDuration the duration of a single simulation step
*/
public Simulation(Updater updater, double stepDuration) {
if(updater == null) {
throw new NullPointerException();
}
if(stepDuration <= 0) {
throw new IllegalArgumentException();
}
this.updater = updater;
this.stepDuration = stepDuration;
}
/**
* Update fuction thats calls the callback as many times as the simulation inverval fits into passed time
* since the last call.
* If the passed time is greated than 100 times the interval, no simulation will take place.
*/
public void update() {
long now = System.nanoTime();
double deltaTime = (now - lastTime) / 1e09 + remainingTime;
if(deltaTime > 100*stepDuration) {
// skip pause
lastTime = now;
remainingTime = 0;
return;
}
while(deltaTime >= stepDuration) {
// fixed rate update
updater.update(stepDuration);
deltaTime -= stepDuration;
}
lastTime = now;
remainingTime = deltaTime;
}
}
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