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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.MathUtils;
import org.jbox2d.common.Settings;
import org.jbox2d.common.Vec2;
import org.jbox2d.pooling.IWorldPool;
import org.jbox2d.pooling.normal.DefaultWorldPool;
// updated to rev 100
/** An axis-aligned bounding box. */
public class AABB {
/** Bottom left vertex of bounding box. */
public final Vec2 lowerBound;
/** Top right vertex of bounding box. */
public final Vec2 upperBound;
/**
* Creates the default object, with vertices at 0,0 and 0,0.
*/
public AABB() {
lowerBound = new Vec2();
upperBound = new Vec2();
}
/**
* Copies from the given object
*
* @param copy
* the object to copy from
*/
public AABB(final AABB copy) {
this(copy.lowerBound, copy.upperBound);
}
/**
* Creates an AABB object using the given bounding vertices.
*
* @param lowerVertex
* the bottom left vertex of the bounding box
* @param maxVertex
* the top right vertex of the bounding box
*/
public AABB(final Vec2 lowerVertex, final Vec2 upperVertex) {
this.lowerBound = lowerVertex.clone(); // clone to be safe
this.upperBound = upperVertex.clone();
}
/**
* Sets this object from the given object
*
* @param aabb
* the object to copy from
*/
public final void set(final AABB aabb) {
lowerBound.set(aabb.lowerBound);
upperBound.set(aabb.upperBound);
}
/** Verify that the bounds are sorted */
public final boolean isValid() {
final float dx = upperBound.x - lowerBound.x;
if (dx < 0f) {
return false;
}
final float dy = upperBound.y - lowerBound.y;
if (dy < 0) {
return false;
}
return lowerBound.isValid() && upperBound.isValid();
}
/**
* Get the center of the AABB
*
* @return
*/
public final Vec2 getCenter() {
final Vec2 center = new Vec2(lowerBound);
center.addLocal(upperBound);
center.mulLocal(.5f);
return center;
}
public final void getCenterToOut(final Vec2 out) {
out.x = (lowerBound.x + upperBound.x) * .5f;
out.y = (lowerBound.y + upperBound.y) * .5f;
}
/**
* Get the extents of the AABB (half-widths).
*
* @return
*/
public final Vec2 getExtents() {
final Vec2 center = new Vec2(upperBound);
center.subLocal(lowerBound);
center.mulLocal(.5f);
return center;
}
public final void getExtentsToOut(final Vec2 out) {
out.x = (upperBound.x - lowerBound.x) * .5f;
out.y = (upperBound.y - lowerBound.y) * .5f; // thanks FDN1
}
public final void getVertices(Vec2[] argRay) {
argRay[0].set(lowerBound);
argRay[1].set(lowerBound);
argRay[1].x += upperBound.x - lowerBound.x;
argRay[2].set(upperBound);
argRay[3].set(upperBound);
argRay[3].x -= upperBound.x - lowerBound.x;
}
/**
* Gets the perimeter length
*
* @return
*/
public final float getPerimeter() {
return 2.0f * (upperBound.x - lowerBound.x + upperBound.y - lowerBound.y);
}
/**
* Combine two AABBs into this one.
*
* @param aabb1
* @param aab
*/
public final void combine(final AABB aabb1, final AABB aab) {
lowerBound.x = aabb1.lowerBound.x < aab.lowerBound.x ? aabb1.lowerBound.x
: aab.lowerBound.x;
lowerBound.y = aabb1.lowerBound.y < aab.lowerBound.y ? aabb1.lowerBound.y
: aab.lowerBound.y;
upperBound.x = aabb1.upperBound.x > aab.upperBound.x ? aabb1.upperBound.x
: aab.upperBound.x;
upperBound.y = aabb1.upperBound.y > aab.upperBound.y ? aabb1.upperBound.y
: aab.upperBound.y;
}
/**
* Does this aabb contain the provided AABB.
*
* @return
*/
public final boolean contains(final AABB aabb) {
/*
* boolean result = true; result = result && lowerBound.x <=
* aabb.lowerBound.x; result = result && lowerBound.y <=
* aabb.lowerBound.y; result = result && aabb.upperBound.x <=
* upperBound.x; result = result && aabb.upperBound.y <= upperBound.y;
* return result;
*/
// djm: faster putting all of them together, as if one is false we leave
// the logic
// early
return lowerBound.x > aabb.lowerBound.x
&& lowerBound.y > aabb.lowerBound.y
&& aabb.upperBound.x > upperBound.x
&& aabb.upperBound.y > upperBound.y;
}
/**
* @deprecated please use
* {@link #raycast(RayCastOutput, RayCastInput, IWorldPool)} for
* better performance
* @param output
* @param input
* @return
*/
public final boolean raycast(final RayCastOutput output,
final RayCastInput input) {
return raycast(output, input, new DefaultWorldPool(4, 4));
}
/**
* From Real-time Collision Detection, p179.
*
* @param output
* @param input
*/
public final boolean raycast(final RayCastOutput output,
final RayCastInput input, IWorldPool argPool) {
float tmin = Float.MIN_VALUE;
float tmax = Float.MAX_VALUE;
final Vec2 p = argPool.popVec2();
final Vec2 d = argPool.popVec2();
final Vec2 absD = argPool.popVec2();
final Vec2 normal = argPool.popVec2();
p.set(input.p1);
d.set(input.p2).subLocal(input.p1);
Vec2.absToOut(d, absD);
// x then y
if (absD.x < Settings.EPSILON) {
// Parallel.
if (p.x < lowerBound.x || upperBound.x < p.x) {
argPool.pushVec2(4);
return false;
}
} else {
final float inv_d = 1.0f / d.x;
float t1 = (lowerBound.x - p.x) * inv_d;
float t2 = (upperBound.x - p.x) * inv_d;
// Sign of the normal vector.
float s = -1.0f;
if (t1 > t2) {
final float temp = t1;
t1 = t2;
t2 = temp;
s = 1.0f;
}
// Push the min up
if (t1 > tmin) {
normal.setZero();
normal.x = s;
tmin = t1;
}
// Pull the max down
tmax = MathUtils.min(tmax, t2);
if (tmin > tmax) {
argPool.pushVec2(4);
return false;
}
}
if (absD.y < Settings.EPSILON) {
// Parallel.
if (p.y < lowerBound.y || upperBound.y < p.y) {
argPool.pushVec2(4);
return false;
}
} else {
final float inv_d = 1.0f / d.y;
float t1 = (lowerBound.y - p.y) * inv_d;
float t2 = (upperBound.y - p.y) * inv_d;
// Sign of the normal vector.
float s = -1.0f;
if (t1 > t2) {
final float temp = t1;
t1 = t2;
t2 = temp;
s = 1.0f;
}
// Push the min up
if (t1 > tmin) {
normal.setZero();
normal.y = s;
tmin = t1;
}
// Pull the max down
tmax = MathUtils.min(tmax, t2);
if (tmin > tmax) {
argPool.pushVec2(4);
return false;
}
}
// Does the ray start inside the box?
// Does the ray intersect beyond the max fraction?
if (tmin < 0.0f || input.maxFraction < tmin) {
argPool.pushVec2(4);
return false;
}
// Intersection.
output.fraction = tmin;
output.normal.x = normal.x;
output.normal.y = normal.y;
argPool.pushVec2(4);
return true;
}
public static final boolean testOverlap(final AABB a, final AABB b) {
if (b.lowerBound.x - a.upperBound.x > 0.0f
|| b.lowerBound.y - a.upperBound.y > 0.0f) {
return false;
}
if (a.lowerBound.x - b.upperBound.x > 0.0f
|| a.lowerBound.y - b.upperBound.y > 0.0f) {
return false;
}
return true;
}
@Override
public final String toString() {
final String s = "AABB[" + lowerBound + " . " + upperBound + "]";
return s;
}
}