org.jbox2d.util.sph.SPHGroup Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of jbox2d-library Show documentation
A 2D java physics engine, a port of the C++ Box2d engine. This is the core physics engine.
There is a newer version: 2.2.1.1
/*******************************************************************************
 * Copyright (c) 2011, Daniel Murphy
 * 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  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 DANIEL MURPHY 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.
 ******************************************************************************/
package org.jbox2d.util.sph;

import org.jbox2d.collision.AABB;
import org.jbox2d.common.MathUtils;
import org.jbox2d.common.Vec2;

//Some default values are in Master.cpp

public class SPHGroup {
	public SmoothParticle[] t;
	public Parameter param;
	
	public SPHGroup(int nParts, AABB aabb, float tStep) {
		// set the parameters to some default values
		param = new Parameter();
		param.numPts 		= nParts;
		param.initVel = new Vec2(0.0f,0.0f);		
		param.machNum      	= 0.5;		
		param.initDensity	= 1000.0;	
		param.initPressure = 10000.0f;
		param.nu 		= 1000.0;
		param.deltaT		= tStep;
		param.numSteps		= 500000;
		param.outputEvery	= 5000;
		param.firstOutput	= 0;
		param.densityVariation   = 0.3;
		param.lengthScale	= 1000.0;
		param.bodyFX 		= 0.0;
		param.bodyFY		= 0.0;
		param.c = 1.0f;
		param.h = 1000.0f;
		t = new SmoothParticle[nParts];
		for (int i=0; i maxAccelSquared)
					maxAccelSquared = accelSquared;
			}	
		}


		double calcDeltaT = 10000000;
		if(maxAccelSquared > 0.0) {
			calcDeltaT = 0.25*Math.sqrt(param.h / Math.sqrt(maxAccelSquared));
		}
		
		if(calcDeltaT < param.deltaT) {
			System.out.println("current DT: " + param.deltaT + " is not small enough.");
			System.out.println("It should be: " + calcDeltaT);
		}
	}
	
	
	/**
	 * Handle a time step, including SPH forces
	 */ 
	public void updateParticles() {
		calcPressure();

		// Interact
		for (int i=0; i