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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.collision.Distance.DistanceProxy;
import org.jbox2d.collision.Distance.SimplexCache;
import org.jbox2d.common.Mat22;
import org.jbox2d.common.MathUtils;
import org.jbox2d.common.Settings;
import org.jbox2d.common.Sweep;
import org.jbox2d.common.Transform;
import org.jbox2d.common.Vec2;
import org.jbox2d.pooling.IWorldPool;
/**
* Class used for computing the time of impact. This class should not be
* constructed usually, just retrieve from the {@link SingletonPool#getTOI()}.
*
* @author daniel
*/
public class TimeOfImpact {
public static final int MAX_ITERATIONS = 1000;
public static int toiCalls = 0;
public static int toiIters = 0;
public static int toiMaxIters = 0;
public static int toiRootIters = 0;
public static int toiMaxRootIters = 0;
/**
* Input parameters for TOI
* @author Daniel Murphy
*/
public static class TOIInput {
public final DistanceProxy proxyA = new DistanceProxy();
public final DistanceProxy proxyB = new DistanceProxy();
public final Sweep sweepA = new Sweep();
public final Sweep sweepB = new Sweep();
/**
* defines sweep interval [0, tMax]
*/
public float tMax;
}
public static enum TOIOutputState {
UNKNOWN, FAILED, OVERLAPPED, TOUCHING, SEPARATED
}
/**
* Output parameters for TimeOfImpact
* @author daniel
*/
public static class TOIOutput {
public TOIOutputState state;
public float t;
}
// djm pooling
private final SimplexCache cache = new SimplexCache();
private final DistanceInput distanceInput = new DistanceInput();
private final Transform xfA = new Transform();
private final Transform xfB = new Transform();
private final DistanceOutput distanceOutput = new DistanceOutput();
private final SeparationFunction fcn = new SeparationFunction();
private final int[] indexes = new int[2];
private final Sweep sweepA = new Sweep();
private final Sweep sweepB = new Sweep();
private final IWorldPool pool;
public TimeOfImpact(IWorldPool argPool){
pool = argPool;
}
/**
* Compute the upper bound on time before two shapes penetrate. Time is represented as
* a fraction between [0,tMax]. This uses a swept separating axis and may miss some
* intermediate,
* non-tunneling collision. If you change the time interval, you should call this
* function
* again.
* Note: use Distance to compute the contact point and normal at the time of impact.
*
* @param output
* @param input
*/
public final void timeOfImpact(TOIOutput output, TOIInput input) {
// CCD via the local separating axis method. This seeks progression
// by computing the largest time at which separation is maintained.
++toiCalls;
output.state = TOIOutputState.UNKNOWN;
output.t = input.tMax;
final DistanceProxy proxyA = input.proxyA;
final DistanceProxy proxyB = input.proxyB;
sweepA.set(input.sweepA);
sweepB.set(input.sweepB);
// Large rotations can make the root finder fail, so we normalize the
// sweep angles.
sweepA.normalize();
sweepB.normalize();
float tMax = input.tMax;
float totalRadius = proxyA.m_radius + proxyB.m_radius;
// djm: whats with all these constants?
float target = MathUtils.max(Settings.linearSlop, totalRadius - 3.0f * Settings.linearSlop);
float tolerance = 0.25f * Settings.linearSlop;
assert (target > tolerance);
float t1 = 0f;
int iter = 0;
cache.count = 0;
distanceInput.proxyA = input.proxyA;
distanceInput.proxyB = input.proxyB;
distanceInput.useRadii = false;
// The outer loop progressively attempts to compute new separating axes.
// This loop terminates when an axis is repeated (no progress is made).
for (;;) {
sweepA.getTransform(xfA, t1);
sweepB.getTransform(xfB, t1);
// System.out.printf("sweepA: %f, %f, sweepB: %f, %f\n",
// sweepA.c.x, sweepA.c.y, sweepB.c.x, sweepB.c.y);
// Get the distance between shapes. We can also use the results
// to get a separating axis
distanceInput.transformA = xfA;
distanceInput.transformB = xfB;
pool.getDistance().distance(distanceOutput, cache, distanceInput);
// System.out.printf("Dist: %f at points %f, %f and %f, %f. %d iterations\n",
// distanceOutput.distance, distanceOutput.pointA.x, distanceOutput.pointA.y,
// distanceOutput.pointB.x, distanceOutput.pointB.y,
// distanceOutput.iterations);
// If the shapes are overlapped, we give up on continuous collision.
if (distanceOutput.distance <= 0f) {
// System.out.println("failure, overlapped");
// Failure!
output.state = TOIOutputState.OVERLAPPED;
output.t = 0f;
break;
}
if (distanceOutput.distance < target + tolerance) {
// System.out.println("touching, victory");
// Victory!
output.state = TOIOutputState.TOUCHING;
output.t = t1;
break;
}
// Initialize the separating axis.
fcn.initialize(cache, proxyA, sweepA, proxyB, sweepB, t1);
// Compute the TOI on the separating axis. We do this by successively
// resolving the deepest point. This loop is bounded by the number of
// vertices.
boolean done = false;
float t2 = tMax;
int pushBackIter = 0;
for (;;) {
// Find the deepest point at t2. Store the witness point indices.
float s2 = fcn.findMinSeparation(indexes, t2);
// System.out.printf("s2: %f\n", s2);
// Is the final configuration separated?
if (s2 > target + tolerance) {
// Victory!
// System.out.println("separated");
output.state = TOIOutputState.SEPARATED;
output.t = tMax;
done = true;
break;
}
// Has the separation reached tolerance?
if (s2 > target - tolerance) {
// System.out.println("advancing");
// Advance the sweeps
t1 = t2;
break;
}
// Compute the initial separation of the witness points.
float s1 = fcn.evaluate(indexes[0], indexes[1], t1);
// Check for initial overlap. This might happen if the root finder
// runs out of iterations.
// System.out.printf("s1: %f, target: %f, tolerance: %f\n", s1, target,
// tolerance);
if (s1 < target - tolerance) {
// System.out.println("failed?");
output.state = TOIOutputState.FAILED;
output.t = t1;
done = true;
break;
}
// Check for touching
if (s1 <= target + tolerance) {
// System.out.println("touching?");
// Victory! t1 should hold the TOI (could be 0.0).
output.state = TOIOutputState.TOUCHING;
output.t = t1;
done = true;
break;
}
// Compute 1D root of: f(x) - target = 0
int rootIterCount = 0;
float a1 = t1, a2 = t2;
for (;;) {
// Use a mix of the secant rule and bisection.
float t;
if ((rootIterCount & 1) == 1) {
// Secant rule to improve convergence.
t = a1 + (target - s1) * (a2 - a1) / (s2 - s1);
}
else {
// Bisection to guarantee progress.
t = 0.5f * (a1 + a2);
}
float s = fcn.evaluate(indexes[0], indexes[1], t);
if (MathUtils.abs(s - target) < tolerance) {
// t2 holds a tentative value for t1
t2 = t;
break;
}
// Ensure we continue to bracket the root.
if (s > target) {
a1 = t;
s1 = s;
}
else {
a2 = t;
s2 = s;
}
++rootIterCount;
++toiRootIters;
// djm: whats with this? put in settings?
if (rootIterCount == 50) {
break;
}
}
toiMaxRootIters = MathUtils.max(toiMaxRootIters, rootIterCount);
++pushBackIter;
if (pushBackIter == Settings.maxPolygonVertices) {
break;
}
}
++iter;
++toiIters;
if (done) {
// System.out.println("done");
break;
}
if (iter == MAX_ITERATIONS) {
// System.out.println("failed, root finder stuck");
// Root finder got stuck. Semi-victory.
output.state = TOIOutputState.FAILED;
output.t = t1;
break;
}
}
// System.out.printf("final sweeps: %f, %f, %f; %f, %f, %f", input.s)
toiMaxIters = MathUtils.max(toiMaxIters, iter);
}
}
enum Type {
POINTS, FACE_A, FACE_B;
}
class SeparationFunction {
public DistanceProxy m_proxyA;
public DistanceProxy m_proxyB;
public Type m_type;
public final Vec2 m_localPoint = new Vec2();
public final Vec2 m_axis = new Vec2();
public Sweep m_sweepA;
public Sweep m_sweepB;
// djm pooling
private final Vec2 localPointA = new Vec2();
private final Vec2 localPointB = new Vec2();
private final Vec2 pointA = new Vec2();
private final Vec2 pointB = new Vec2();
private final Vec2 localPointA1 = new Vec2();
private final Vec2 localPointA2 = new Vec2();
private final Vec2 normal = new Vec2();
private final Vec2 localPointB1 = new Vec2();
private final Vec2 localPointB2 = new Vec2();
private final Vec2 temp = new Vec2();
private final Transform xfa = new Transform();
private final Transform xfb = new Transform();
// TODO_ERIN might not need to return the separation
public float initialize(final SimplexCache cache, final DistanceProxy proxyA, final Sweep sweepA,
final DistanceProxy proxyB, final Sweep sweepB, float t1) {
m_proxyA = proxyA;
m_proxyB = proxyB;
int count = cache.count;
assert (0 < count && count < 3);
m_sweepA = sweepA;
m_sweepB = sweepB;
m_sweepA.getTransform(xfa, t1);
m_sweepB.getTransform(xfb, t1);
// log.debug("initializing separation.\n" +
// "cache: "+cache.count+"-"+cache.metric+"-"+cache.indexA+"-"+cache.indexB+"\n"
// "distance: "+proxyA.
if (count == 1) {
m_type = Type.POINTS;
/*
* Vec2 localPointA = m_proxyA.GetVertex(cache.indexA[0]);
* Vec2 localPointB = m_proxyB.GetVertex(cache.indexB[0]);
* Vec2 pointA = Mul(transformA, localPointA);
* Vec2 pointB = Mul(transformB, localPointB);
* m_axis = pointB - pointA;
* m_axis.Normalize();
*/
localPointA.set(m_proxyA.getVertex(cache.indexA[0]));
localPointB.set(m_proxyB.getVertex(cache.indexB[0]));
Transform.mulToOut(xfa, localPointA, pointA);
Transform.mulToOut(xfb, localPointB, pointB);
m_axis.set(pointB).subLocal(pointA);
float s = m_axis.normalize();
return s;
}
else if (cache.indexA[0] == cache.indexA[1]) {
// Two points on B and one on A.
m_type = Type.FACE_B;
localPointB1.set(m_proxyB.getVertex(cache.indexB[0]));
localPointB2.set(m_proxyB.getVertex(cache.indexB[1]));
temp.set(localPointB2).subLocal(localPointB1);
Vec2.crossToOut(temp, 1f, m_axis);
m_axis.normalize();
Mat22.mulToOut(xfb.R, m_axis, normal);
m_localPoint.set(localPointB1).addLocal(localPointB2).mulLocal(.5f);
Transform.mulToOut(xfb, m_localPoint, pointB);
localPointA.set(proxyA.getVertex(cache.indexA[0]));
Transform.mulToOut(xfa, localPointA, pointA);
temp.set(pointA).subLocal(pointB);
float s = Vec2.dot(temp, normal);
if (s < 0.0f) {
m_axis.negateLocal();
s = -s;
}
return s;
}
else {
// Two points on A and one or two points on B.
m_type = Type.FACE_A;
localPointA1.set(m_proxyA.getVertex(cache.indexA[0]));
localPointA2.set(m_proxyA.getVertex(cache.indexA[1]));
temp.set(localPointA2).subLocal(localPointA1);
Vec2.crossToOut(temp, 1.0f, m_axis);
m_axis.normalize();
Mat22.mulToOut(xfa.R, m_axis, normal);
m_localPoint.set(localPointA1).addLocal(localPointA2).mulLocal(.5f);
Transform.mulToOut(xfa, m_localPoint, pointA);
localPointB.set(m_proxyB.getVertex(cache.indexB[0]));
Transform.mulToOut(xfb, localPointB, pointB);
temp.set(pointB).subLocal(pointA);
float s = Vec2.dot(temp, normal);
if (s < 0.0f) {
m_axis.negateLocal();
s = -s;
}
return s;
}
}
private final Vec2 axisA = new Vec2();
private final Vec2 axisB = new Vec2();
// float FindMinSeparation(int* indexA, int* indexB, float t) const
public float findMinSeparation(int[] indexes, float t) {
m_sweepA.getTransform(xfa, t);
m_sweepB.getTransform(xfb, t);
switch (m_type) {
case POINTS : {
Mat22.mulTransToOut(xfa.R, m_axis, axisA);
Mat22.mulTransToOut(xfb.R, m_axis.negateLocal(), axisB);
m_axis.negateLocal();
indexes[0] = m_proxyA.getSupport(axisA);
indexes[1] = m_proxyB.getSupport(axisB);
localPointA.set(m_proxyA.getVertex(indexes[0]));
localPointB.set(m_proxyB.getVertex(indexes[1]));
Transform.mulToOut(xfa, localPointA, pointA);
Transform.mulToOut(xfb, localPointB, pointB);
float separation = Vec2.dot(pointB.subLocal(pointA), m_axis);
return separation;
}
case FACE_A : {
Mat22.mulToOut(xfa.R, m_axis, normal);
Transform.mulToOut(xfa, m_localPoint, pointA);
Mat22.mulTransToOut(xfb.R, normal.negateLocal(), axisB);
normal.negateLocal();
indexes[0] = -1;
indexes[1] = m_proxyB.getSupport(axisB);
localPointB.set(m_proxyB.getVertex(indexes[1]));
Transform.mulToOut(xfb, localPointB, pointB);
float separation = Vec2.dot(pointB.subLocal(pointA), normal);
return separation;
}
case FACE_B : {
Mat22.mulToOut(xfb.R, m_axis, normal);
Transform.mulToOut(xfb, m_localPoint, pointB);
Mat22.mulTransToOut(xfa.R, normal.negateLocal(), axisA);
normal.negateLocal();
indexes[1] = -1;
indexes[0] = m_proxyA.getSupport(axisA);
localPointA.set(m_proxyA.getVertex(indexes[0]));
Transform.mulToOut(xfa, localPointA, pointA);
float separation = Vec2.dot(pointA.subLocal(pointB), normal);
return separation;
}
default :
assert (false);
indexes[0] = -1;
indexes[1] = -1;
return 0f;
}
}
public float evaluate(int indexA, int indexB, float t) {
m_sweepA.getTransform(xfa, t);
m_sweepB.getTransform(xfb, t);
switch (m_type) {
case POINTS : {
Mat22.mulTransToOut(xfa.R, m_axis, axisA);
Mat22.mulTransToOut(xfb.R, m_axis.negateLocal(), axisB);
m_axis.negateLocal();
localPointA.set(m_proxyA.getVertex(indexA));
localPointB.set(m_proxyB.getVertex(indexB));
Transform.mulToOut(xfa, localPointA, pointA);
Transform.mulToOut(xfb, localPointB, pointB);
float separation = Vec2.dot(pointB.subLocal(pointA), m_axis);
return separation;
}
case FACE_A : {
// System.out.printf("We're faceA\n");
Mat22.mulToOut(xfa.R, m_axis, normal);
Transform.mulToOut(xfa, m_localPoint, pointA);
Mat22.mulTransToOut(xfb.R, normal.negateLocal(), axisB);
normal.negateLocal();
localPointB.set(m_proxyB.getVertex(indexB));
Transform.mulToOut(xfb, localPointB, pointB);
float separation = Vec2.dot(pointB.subLocal(pointA), normal);
return separation;
}
case FACE_B : {
// System.out.printf("We're faceB\n");
Mat22.mulToOut(xfb.R, m_axis, normal);
Transform.mulToOut(xfb, m_localPoint, pointB);
Mat22.mulTransToOut(xfa.R, normal.negateLocal(), axisA);
normal.negateLocal();
localPointA.set(m_proxyA.getVertex(indexA));
Transform.mulToOut(xfa, localPointA, pointA);
float separation = Vec2.dot(pointA.subLocal(pointB), normal);
return separation;
}
default :
assert (false);
return 0f;
}
}
}