/*******************************************************************************
* Copyright (c) 2013, Daniel Murphy
* All rights reserved.
*
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* are permitted provided that the following conditions are met:
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*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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******************************************************************************/
package org.jbox2d.collision;
import org.jbox2d.common.MathUtils;
import org.jbox2d.common.Rot;
import org.jbox2d.common.Settings;
import org.jbox2d.common.Transform;
import org.jbox2d.common.Vec2;
/**
* 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;
/**
* A negative value indicates overlap, in meters.
*/
public final float[] separations;
public WorldManifold() {
normal = new Vec2();
points = new Vec2[Settings.maxManifoldPoints];
separations = new float[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.x = 1;
normal.y = 0;
Vec2 v = manifold.localPoint;
// Transform.mulToOutUnsafe(xfA, manifold.localPoint, pointA);
// Transform.mulToOutUnsafe(xfB, manifold.points[0].localPoint, pointB);
pointA.x = (xfA.q.c * v.x - xfA.q.s * v.y) + xfA.p.x;
pointA.y = (xfA.q.s * v.x + xfA.q.c * v.y) + xfA.p.y;
Vec2 mp0p = manifold.points[0].localPoint;
pointB.x = (xfB.q.c * mp0p.x - xfB.q.s * mp0p.y) + xfB.p.x;
pointB.y = (xfB.q.s * mp0p.x + xfB.q.c * mp0p.y) + xfB.p.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;
separations[0] = (cBx - cAx) * normal.x + (cBy - cAy) * normal.y;
}
break;
case FACE_A: {
final Vec2 planePoint = pool3;
Rot.mulToOutUnsafe(xfA.q, 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 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;
separations[i] = (cBx - cAx) * normal.x + (cBy - cAy) * normal.y;
}
}
break;
case FACE_B:
final Vec2 planePoint = pool3;
Rot.mulToOutUnsafe(xfB.q, manifold.localNormal, normal);
Transform.mulToOut(xfB, manifold.localPoint, planePoint);
// final Mat22 R = xfB.q;
// normal.x = R.ex.x * manifold.localNormal.x + R.ey.x * manifold.localNormal.y;
// normal.y = R.ex.y * manifold.localNormal.x + R.ey.y * manifold.localNormal.y;
// final Vec2 v = manifold.localPoint;
// planePoint.x = xfB.p.x + xfB.q.ex.x * v.x + xfB.q.ey.x * v.y;
// planePoint.y = xfB.p.y + xfB.q.ex.y * v.x + xfB.q.ey.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.p.x + xfA.q.ex.x * manifold.points[i].localPoint.x + xfA.q.ey.x *
// manifold.points[i].localPoint.y;
// clipPoint.y = xfA.p.y + xfA.q.ex.y * manifold.points[i].localPoint.x + xfA.q.ey.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;
separations[i] = (cAx - cBx) * normal.x + (cAy - cBy) * normal.y;
}
// Ensure normal points from A to B.
normal.x = -normal.x;
normal.y = -normal.y;
break;
}
}
}