/*
* Phys2D - a 2D physics engine based on the work of Erin Catto.
*
* This source is provided under the terms of the BSD License.
*
* Copyright (c) 2006, Phys2D
* 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 Phys2D/New Dawn Software 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 THE COPYRIGHT OWNER 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 net.phys2d.raw.collide;
import net.phys2d.math.ROVector2f;
import net.phys2d.math.Vector2f;
import net.phys2d.raw.Body;
import net.phys2d.raw.Contact;
import net.phys2d.raw.shapes.Circle;
import net.phys2d.raw.shapes.Line;
/**
* Collision routines betwene a circle and a line. The create method is
* provided in case this collider becomes stateful at some point.
*
* @author Kevin Glass
*/
public strictfp class LineCircleCollider implements Collider {
/**
* @see net.phys2d.raw.collide.Collider#collide(net.phys2d.raw.Contact[], net.phys2d.raw.Body, net.phys2d.raw.Body)
*/
public int collide(Contact[] contacts, Body bodyA, Body bodyB) {
Line line = (Line) bodyA.getShape();
Circle circle = (Circle) bodyB.getShape();
Vector2f[] vertsA = line.getVertices(bodyA.getPosition(), bodyA.getRotation());
// compute intersection of the line A and a line parallel to
// the line A's normal passing through the origin of B
Vector2f startA = vertsA[0];
Vector2f endA = vertsA[1];
ROVector2f startB = bodyB.getPosition();
Vector2f endB = new Vector2f(endA);
endB.sub(startA);
endB.set(endB.y, -endB.x);
// endB.add(startB);// TODO: inline endB into equations below, this last operation will be useless..
//TODO: reuse mathutil.intersect
// float d = (endB.y - startB.getY()) * (endA.x - startA.x);
// d -= (endB.x - startB.getX()) * (endA.y - startA.y);
//
// float uA = (endB.x - startB.getX()) * (startA.y - startB.getY());
// uA -= (endB.y - startB.getY()) * (startA.x - startB.getX());
// uA /= d;
float d = endB.y * (endA.x - startA.x);
d -= endB.x * (endA.y - startA.y);
float uA = endB.x * (startA.y - startB.getY());
uA -= endB.y * (startA.x - startB.getX());
uA /= d;
Vector2f position = null;
if ( uA < 0 ) { // the intersection is somewhere before startA
position = startA;
} else if ( uA > 1 ) { // the intersection is somewhere after endA
position = endA;
} else {
position = new Vector2f(
startA.x + uA * (endA.x - startA.x),
startA.y + uA * (endA.y - startA.y));
}
Vector2f normal = endB; // reuse of vector object
normal.set(startB);
normal.sub(position);
float distSquared = normal.lengthSquared();
float radiusSquared = circle.getRadius() * circle.getRadius();
if ( distSquared < radiusSquared ) {
contacts[0].setPosition(position);
contacts[0].setFeature(new FeaturePair());
normal.normalise();
contacts[0].setNormal(normal);
float separation = (float) Math.sqrt(distSquared) - circle.getRadius();
contacts[0].setSeparation(separation);
return 1;
}
return 0;
}
}