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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.
******************************************************************************/
package org.jbox2d.collision;
import org.jbox2d.common.Mat22;
import org.jbox2d.common.MathUtils;
import org.jbox2d.common.Settings;
import org.jbox2d.common.Transform;
import org.jbox2d.common.Vec2;
// updated to rev 100
/**
* This is used to compute the current state of a contact manifold.
*
* @author daniel
*/
public class WorldManifold {
/**
* World vector pointing from A to B
*/
public final Vec2 normal;
/**
* World contact point (point of intersection)
*/
public final Vec2[] points;
public WorldManifold() {
normal = new Vec2();
points = new Vec2[Settings.maxManifoldPoints];
for (int i = 0; i < Settings.maxManifoldPoints; i++) {
points[i] = new Vec2();
}
}
private final Vec2 pool3 = new Vec2();
private final Vec2 pool4 = new Vec2();
public final void initialize(final Manifold manifold, final Transform xfA, float radiusA, final Transform xfB,
float radiusB) {
if (manifold.pointCount == 0) {
return;
}
switch (manifold.type) {
case CIRCLES :{
// final Vec2 pointA = pool3;
// final Vec2 pointB = pool4;
//
// normal.set(1, 0);
// Transform.mulToOut(xfA, manifold.localPoint, pointA);
// Transform.mulToOut(xfB, manifold.points[0].localPoint, pointB);
//
// if (MathUtils.distanceSquared(pointA, pointB) > Settings.EPSILON * Settings.EPSILON) {
// normal.set(pointB).subLocal(pointA);
// normal.normalize();
// }
//
// cA.set(normal).mulLocal(radiusA).addLocal(pointA);
// cB.set(normal).mulLocal(radiusB).subLocal(pointB).negateLocal();
// points[0].set(cA).addLocal(cB).mulLocal(0.5f);
final Vec2 pointA = pool3;
final Vec2 pointB = pool4;
normal.x = 1;
normal.y = 0;
pointA.x = xfA.position.x + xfA.R.col1.x * manifold.localPoint.x + xfA.R.col2.x * manifold.localPoint.y;
pointA.y = xfA.position.y + xfA.R.col1.y * manifold.localPoint.x + xfA.R.col2.y * manifold.localPoint.y;
pointB.x = xfB.position.x + xfB.R.col1.x * manifold.points[0].localPoint.x + xfB.R.col2.x * manifold.points[0].localPoint.y;
pointB.y = xfB.position.y + xfB.R.col1.y * manifold.points[0].localPoint.x + xfB.R.col2.y * manifold.points[0].localPoint.y;
if (MathUtils.distanceSquared(pointA, pointB) > Settings.EPSILON * Settings.EPSILON) {
normal.x = pointB.x - pointA.x;
normal.y = pointB.y - pointA.y;
normal.normalize();
}
final float cAx = normal.x * radiusA + pointA.x;
final float cAy = normal.y * radiusA + pointA.y;
final float cBx = -normal.x * radiusB + pointB.x;
final float cBy = -normal.y * radiusB + pointB.y;
points[0].x = (cAx + cBx) *.5f;
points[0].y = (cAy + cBy) *.5f;
}
break;
case FACE_A : {
// final Vec2 planePoint = pool3;
//
// Mat22.mulToOut(xfA.R, manifold.localNormal, normal);
// Transform.mulToOut(xfA, manifold.localPoint, planePoint);
//
// final Vec2 clipPoint = pool4;
//
// for (int i = 0; i < manifold.pointCount; i++) {
// // b2Vec2 clipPoint = b2Mul(xfB, manifold->points[i].localPoint);
// // b2Vec2 cA = clipPoint + (radiusA - b2Dot(clipPoint - planePoint,
// // normal)) * normal;
// // b2Vec2 cB = clipPoint - radiusB * normal;
// // points[i] = 0.5f * (cA + cB);
// Transform.mulToOut(xfB, manifold.points[i].localPoint, clipPoint);
// // use cA as temporary for now
// cA.set(clipPoint).subLocal(planePoint);
// float scalar = radiusA - Vec2.dot(cA, normal);
// cA.set(normal).mulLocal(scalar).addLocal(clipPoint);
// cB.set(normal).mulLocal(radiusB).subLocal(clipPoint).negateLocal();
// points[i].set(cA).addLocal(cB).mulLocal(0.5f);
// }
final Vec2 planePoint = pool3;
normal.x = xfA.R.col1.x * manifold.localNormal.x + xfA.R.col2.x * manifold.localNormal.y;
normal.y = xfA.R.col1.y * manifold.localNormal.x + xfA.R.col2.y * manifold.localNormal.y;
planePoint.x = xfA.position.x + xfA.R.col1.x * manifold.localPoint.x + xfA.R.col2.x * manifold.localPoint.y;
planePoint.y = xfA.position.y + xfA.R.col1.y * manifold.localPoint.x + xfA.R.col2.y * manifold.localPoint.y;
final Vec2 clipPoint = pool4;
for (int i = 0; i < manifold.pointCount; i++) {
// b2Vec2 clipPoint = b2Mul(xfB, manifold->points[i].localPoint);
// b2Vec2 cA = clipPoint + (radiusA - b2Dot(clipPoint - planePoint,
// normal)) * normal;
// b2Vec2 cB = clipPoint - radiusB * normal;
// points[i] = 0.5f * (cA + cB);
clipPoint.x = xfB.position.x + xfB.R.col1.x * manifold.points[i].localPoint.x + xfB.R.col2.x * manifold.points[i].localPoint.y;
clipPoint.y = xfB.position.y + xfB.R.col1.y * manifold.points[i].localPoint.x + xfB.R.col2.y * manifold.points[i].localPoint.y;
final float scalar = radiusA - ((clipPoint.x - planePoint.x) * normal.x + (clipPoint.y - planePoint.y) * normal.y);
final float cAx = normal.x * scalar + clipPoint.x;
final float cAy = normal.y * scalar + clipPoint.y;
final float cBx = - normal.x * radiusB + clipPoint.x;
final float cBy = - normal.y * radiusB + clipPoint.y;
points[i].x = (cAx + cBx)*.5f;
points[i].y = (cAy + cBy)*.5f;
}
}
break;
case FACE_B :
final Vec2 planePoint = pool3;
final Mat22 R = xfB.R;
normal.x = R.col1.x * manifold.localNormal.x + R.col2.x * manifold.localNormal.y;
normal.y = R.col1.y * manifold.localNormal.x + R.col2.y * manifold.localNormal.y;
final Vec2 v = manifold.localPoint;
planePoint.x = xfB.position.x + xfB.R.col1.x * v.x + xfB.R.col2.x * v.y;
planePoint.y = xfB.position.y + xfB.R.col1.y * v.x + xfB.R.col2.y * v.y;
final Vec2 clipPoint = pool4;
for (int i = 0; i < manifold.pointCount; i++) {
// b2Vec2 clipPoint = b2Mul(xfA, manifold->points[i].localPoint);
// b2Vec2 cB = clipPoint + (radiusB - b2Dot(clipPoint - planePoint,
// normal)) * normal;
// b2Vec2 cA = clipPoint - radiusA * normal;
// points[i] = 0.5f * (cA + cB);
// Transform.mulToOut(xfA, manifold.points[i].localPoint, clipPoint);
// cB.set(clipPoint).subLocal(planePoint);
// float scalar = radiusB - Vec2.dot(cB, normal);
// cB.set(normal).mulLocal(scalar).addLocal(clipPoint);
// cA.set(normal).mulLocal(radiusA).subLocal(clipPoint).negateLocal();
// points[i].set(cA).addLocal(cB).mulLocal(0.5f);
// points[i] = 0.5f * (cA + cB);
clipPoint.x = xfA.position.x + xfA.R.col1.x * manifold.points[i].localPoint.x + xfA.R.col2.x * manifold.points[i].localPoint.y;
clipPoint.y = xfA.position.y + xfA.R.col1.y * manifold.points[i].localPoint.x + xfA.R.col2.y * manifold.points[i].localPoint.y;
final float scalar = radiusB - ((clipPoint.x - planePoint.x) * normal.x + (clipPoint.y - planePoint.y) * normal.y);
final float cBx = normal.x * scalar + clipPoint.x;
final float cBy = normal.y * scalar + clipPoint.y;
final float cAx = - normal.x * radiusA + clipPoint.x;
final float cAy = - normal.y * radiusA + clipPoint.y;
points[i].x = (cAx + cBx) *.5f;
points[i].y = (cAy + cBy) *.5f;
}
// Ensure normal points from A to B.
normal.x = -normal.x;
normal.y = -normal.y;
break;
}
}
}