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A 2D java physics engine, a port of the C++ Box2d engine. This is the core physics engine.
/*******************************************************************************
* 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.
*
* 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.
******************************************************************************/
/*
* JBox2D - A Java Port of Erin Catto's Box2D
*
* JBox2D homepage: http://jbox2d.sourceforge.net/
* Box2D homepage: http://www.box2d.org
*
* This software is provided 'as-is', without any express or implied
* warranty. In no event will the authors be held liable for any damages
* arising from the use of this software.
*
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
*
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/
package org.jbox2d.common;
import java.io.Serializable;
// updated to rev 100
/**
* This describes the motion of a body/shape for TOI computation.
* Shapes are defined with respect to the body origin, which may
* no coincide with the center of mass. However, to support dynamics
* we must interpolate the center of mass position.
*/
public class Sweep implements Serializable {
private static final long serialVersionUID = 1L;
/** Local center of mass position */
public final Vec2 localCenter;
/** Center world positions */
public final Vec2 c0, c;
/** World angles */
public float a0, a;
public String toString() {
String s = "Sweep:\nlocalCenter: " + localCenter + "\n";
s += "c0: " + c0 + ", c: " + c + "\n";
s += "a0: " + a0 + ", a: " + a + "\n";
return s;
}
public Sweep() {
localCenter = new Vec2();
c0 = new Vec2();
c = new Vec2();
}
public final void normalize() {
float d = MathUtils.TWOPI * MathUtils.floor(a0 / MathUtils.TWOPI);
a0 -= d;
a -= d;
}
public final Sweep set(Sweep argCloneFrom) {
localCenter.set(argCloneFrom.localCenter);
c0.set(argCloneFrom.c0);
c.set(argCloneFrom.c);
a0 = argCloneFrom.a0;
a = argCloneFrom.a;
return this;
}
/**
* Get the interpolated transform at a specific time.
*
* @param xf
* the result is placed here - must not be null
* @param t
* the normalized time in [0,1].
*/
public final void getTransform(final Transform xf, final float alpha) {
assert (xf != null);
// if (xf == null)
// xf = new XForm();
// center = p + R * localCenter
/*
* if (1.0f - t0 > Settings.EPSILON) {
* float alpha = (t - t0) / (1.0f - t0);
* xf.position.x = (1.0f - alpha) * c0.x + alpha * c.x;
* xf.position.y = (1.0f - alpha) * c0.y + alpha * c.y;
* float angle = (1.0f - alpha) * a0 + alpha * a;
* xf.R.set(angle);
* } else {
* xf.position.set(c);
* xf.R.set(a);
* }
*/
xf.position.x = (1.0f - alpha) * c0.x + alpha * c.x;
xf.position.y = (1.0f - alpha) * c0.y + alpha * c.y;
// float angle = (1.0f - alpha) * a0 + alpha * a;
// xf.R.set(angle);
xf.R.set((1.0f - alpha) * a0 + alpha * a);
// Shift to origin
// xf.position.subLocal(Mat22.mul(xf.R, localCenter));
xf.position.x -= xf.R.col1.x * localCenter.x + xf.R.col2.x * localCenter.y;
xf.position.y -= xf.R.col1.y * localCenter.x + xf.R.col2.y * localCenter.y;
}
/**
* Advance the sweep forward, yielding a new initial state.
*
* @param t
* the new initial time.
*/
public final void advance(final float t) {
// c0 = (1.0f - t) * c0 + t*c;
c0.x = (1.0f - t) * c0.x + t * c.x;
c0.y = (1.0f - t) * c0.y + t * c.y;
a0 = (1.0f - t) * a0 + t * a;
}
}