/*
* __ .__ .__ ._____.
* _/ |_ _______ __|__| ____ | | |__\_ |__ ______
* \ __\/ _ \ \/ / |/ ___\| | | || __ \ / ___/
* | | ( <_> > <| \ \___| |_| || \_\ \\___ \
* |__| \____/__/\_ \__|\___ >____/__||___ /____ >
* \/ \/ \/ \/
*
* Copyright (c) 2006-2011 Karsten Schmidt
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* http://creativecommons.org/licenses/LGPL/2.1/
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
*/
package toxi.physics2d.behaviors;
import java.util.List;
import toxi.geom.SpatialIndex;
import toxi.geom.Vec2D;
import toxi.physics2d.VerletParticle2D;
public class AttractionBehavior2D implements ParticleBehavior2D {
protected Vec2D attractor;
protected float attrStrength;
protected float radius, radiusSquared;
protected float strength;
protected float jitter;
protected float timeStep;
public AttractionBehavior2D(Vec2D attractor, float radius, float strength) {
this(attractor, radius, strength, 0);
}
public AttractionBehavior2D(Vec2D attractor, float radius, float strength,
float jitter) {
this.attractor = attractor;
this.strength = strength;
this.jitter = jitter;
setRadius(radius);
}
public void apply(VerletParticle2D p) {
Vec2D delta = attractor.sub(p);
float dist = delta.magSquared();
if (dist < radiusSquared) {
Vec2D f = delta.normalizeTo((1.0f - dist / radiusSquared))
.jitter(jitter).scaleSelf(attrStrength);
p.addForce(f);
}
}
public void applyWithIndex(SpatialIndex<Vec2D> spaceHash) {
List<Vec2D> selection = spaceHash.itemsWithinRadius(attractor, radius,
null);
final Vec2D temp = new Vec2D();
if (selection != null) {
for (Vec2D p : selection) {
temp.set(p);
apply((VerletParticle2D) p);
spaceHash.reindex(temp, p);
}
}
}
public void configure(float timeStep) {
this.timeStep = timeStep;
setStrength(strength);
}
/**
* @return the attractor
*/
public Vec2D getAttractor() {
return attractor;
}
/**
* @return the jitter
*/
public float getJitter() {
return jitter;
}
/**
* @return the radius
*/
public float getRadius() {
return radius;
}
/**
* @return the strength
*/
public float getStrength() {
return strength;
}
/**
* @param attractor
* the attractor to set
*/
public void setAttractor(Vec2D attractor) {
this.attractor = attractor;
}
/**
* @param jitter
* the jitter to set
*/
public void setJitter(float jitter) {
this.jitter = jitter;
}
public void setRadius(float r) {
this.radius = r;
this.radiusSquared = r * r;
}
/**
* @param strength
* the strength to set
*/
public void setStrength(float strength) {
this.strength = strength;
this.attrStrength = strength * timeStep;
}
public boolean supportsSpatialIndex() {
return true;
}
}