/*******************************************************************************
* 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.
* * Neither the name of the <organization> nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* 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 DANIEL MURPHY 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.collision.shapes;
import org.jbox2d.collision.AABB;
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;
import org.jbox2d.structs.collision.RayCastInput;
import org.jbox2d.structs.collision.RayCastOutput;
//Updated to rev 100
/**
* A circle shape.
*/
public class CircleShape extends Shape {
public final Vec2 m_p;
private final Vec2 pool1 = new Vec2();
private final Vec2 pool2 = new Vec2();
private final Vec2 pool3 = new Vec2();
/**
* this is used internally, instead use {@link Body#createShape(ShapeDef)} with a
* {@link CircleDef}
*
* @see Body#createShape(ShapeDef)
* @see CircleDef
* @param def
*/
public CircleShape() {
m_type = ShapeType.CIRCLE;
m_p = new Vec2();
m_radius = 0;
}
public final Shape clone() {
CircleShape shape = new CircleShape();
shape.m_p.set(m_p);
shape.m_radius = m_radius;
return shape;
}
/**
* Get the supporting vertex index in the given direction.
*
* @param d
* @return
*/
public final int getSupport(final Vec2 d) {
return 0;
}
/**
* Get the supporting vertex in the given direction.
*
* @param d
* @return
*/
public final Vec2 getSupportVertex(final Vec2 d) {
return m_p;
}
/**
* Get the vertex count.
*
* @return
*/
public final int getVertexCount() {
return 1;
}
/**
* Get a vertex by index.
*
* @param index
* @return
*/
public final Vec2 getVertex(final int index) {
assert (index == 0);
return m_p;
}
/**
* @see Shape#testPoint(Transform, Vec2)
*/
@Override
public final boolean testPoint(final Transform transform, final Vec2 p) {
final Vec2 center = pool1;
Mat22.mulToOut(transform.R, m_p, center);
center.addLocal(transform.position);
final Vec2 d = center.subLocal(p).negateLocal();
return Vec2.dot(d, d) <= m_radius * m_radius;
}
// Collision Detection in Interactive 3D Environments by Gino van den Bergen
// From Section 3.1.2
// x = s + a * r
// norm(x) = radius
/**
* @see Shape#raycast(org.jbox2d.structs.collision.RayCastOutput,
* org.jbox2d.structs.collision.RayCastInput, org.jbox2d.common.Transform, int)
*/
@Override
public final boolean raycast(RayCastOutput argOutput, RayCastInput argInput, Transform argTransform) {
final Vec2 position = pool1;
final Vec2 s = pool2;
final Vec2 r = pool3;
Mat22.mulToOut(argTransform.R, m_p, position);
position.addLocal(argTransform.position);
s.set(argInput.p1).subLocal(position);
final float b = Vec2.dot(s, s) - m_radius * m_radius;
// Solve quadratic equation.
r.set(argInput.p2).subLocal(argInput.p1);
final float c = Vec2.dot(s, r);
final float rr = Vec2.dot(r, r);
final float sigma = c * c - rr * b;
// Check for negative discriminant and short segment.
if (sigma < 0.0f || rr < Settings.EPSILON) {
return false;
}
// Find the point of intersection of the line with the circle.
float a = -(c + MathUtils.sqrt(sigma));
// Is the intersection point on the segment?
if (0.0f <= a && a <= argInput.maxFraction * rr) {
a /= rr;
argOutput.fraction = a;
argOutput.normal.set(r).mulLocal(a);
argOutput.normal.addLocal(s);
argOutput.normal.normalize();
return true;
}
return false;
}
/**
* @see org.jbox2d.collision.shapes.Shape#computeAABB(org.jbox2d.collision.AABB,
* org.jbox2d.common.Transform, int)
*/
@Override
public final void computeAABB(final AABB argAabb, final Transform argTransform) {
final Vec2 p = pool1;
Mat22.mulToOut(argTransform.R, m_p, p);
p.addLocal(argTransform.position);
argAabb.lowerBound.x = p.x - m_radius;
argAabb.lowerBound.y = p.y - m_radius;
argAabb.upperBound.x = p.x + m_radius;
argAabb.upperBound.y = p.y + m_radius;
}
/**
* @see Shape#computeMass(MassData, float)
*/
@Override
public final void computeMass(final MassData massData, final float density) {
massData.mass = density * Settings.PI * m_radius * m_radius;
massData.center.set(m_p);
// inertia about the local origin
massData.I = massData.mass * (0.5f * m_radius * m_radius + Vec2.dot(m_p, m_p));
}
// djm pooled from above
/*
* @see Shape#computeSubmergedArea(Vec2, float, Vec2, Vec2)
* @Override
* public final float computeSubmergedArea( final Vec2 normal, final float offset,
* final Transform xf, final Vec2 c) {
* final Vec2 p = tlp.get();
* Transform.mulToOut(xf,m_p, p);
* final float l = -( Vec2.dot(normal,p) - offset);
* if( l < -m_radius + Settings.EPSILON){
* //Completely dry
* return 0;
* }
* if(l > m_radius){
* //Completely wet
* c.set(p);
* return (float)Math.PI*m_radius*m_radius;
* }
* //Magic
* final float r2 = m_radius*m_radius;
* final float l2 = l*l;
* //Erin TODO: write Sqrt to handle fixed point case.
* final float area = (float) (r2 * (Math.asin(l/m_radius) + Math.PI/2)+ l *
* Math.sqrt(r2 - l2));
* final float com = (float) (-2.0/3.0* Math.pow(r2-l2,1.5f)/area);
* c.x = p.x + normal.x * com;
* c.y = p.y + normal.y * com;
* return area;
* }
*/
}