CollisionProcessing.java

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 * Copyright (c) 2011, Daniel Murphy
 * All rights reserved.
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 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
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 * 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
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/**
 * Created at 2:51:18 PM Jan 23, 2011
 */
package org.jbox2d.gwt.showcase.client.example;

import java.util.HashSet;

import org.jbox2d.collision.shapes.CircleShape;
import org.jbox2d.collision.shapes.PolygonShape;
import org.jbox2d.common.MathUtils;
import org.jbox2d.common.Vec2;
import org.jbox2d.dynamics.Body;
import org.jbox2d.dynamics.BodyDef;
import org.jbox2d.dynamics.BodyType;
import org.jbox2d.dynamics.FixtureDef;
import org.jbox2d.gwt.showcase.client.framework.BaseExample;
import org.jbox2d.gwt.showcase.client.framework.ContactPoint;
import org.jbox2d.gwt.showcase.client.framework.ShowcaseSettings;

/**
 * @author Daniel Murphy
 */
public class CollisionProcessing extends BaseExample {
	
	/**
	 * @see org.jbox2d.testbed.framework.TestbedTest#initTest()
	 */
	@Override
	public void initTest() {
		// Ground body
		{
			PolygonShape shape = new PolygonShape();
			shape.setAsEdge(new Vec2(-50.0f, 0.0f), new Vec2(50.0f, 0.0f));
			
			FixtureDef sd = new FixtureDef();
			sd.shape = shape;
			
			BodyDef bd = new BodyDef();
			Body ground = m_world.createBody(bd);
			ground.createFixture(sd);
		}
		
		float xLo = -5.0f, xHi = 5.0f;
		float yLo = 2.0f, yHi = 35.0f;
		
		// Small triangle
		Vec2 vertices[] = new Vec2[3];
		vertices[0] = new Vec2(-1.0f, 0.0f);
		vertices[1] = new Vec2(1.0f, 0.0f);
		vertices[2] = new Vec2(0.0f, 2.0f);
		
		PolygonShape polygon = new PolygonShape();
		polygon.set(vertices, 3);
		
		FixtureDef triangleShapeDef = new FixtureDef();
		triangleShapeDef.shape = polygon;
		triangleShapeDef.density = 1.0f;
		
		BodyDef triangleBodyDef = new BodyDef();
		triangleBodyDef.type = BodyType.DYNAMIC;
		triangleBodyDef.position.set(MathUtils.randomFloat(xLo, xHi), MathUtils.randomFloat(yLo, yHi));
		
		Body body1 = m_world.createBody(triangleBodyDef);
		body1.createFixture(triangleShapeDef);
		
		// Large triangle (recycle definitions)
		vertices[0].mulLocal(2.0f);
		vertices[1].mulLocal(2.0f);
		vertices[2].mulLocal(2.0f);
		polygon.set(vertices, 3);
		
		triangleBodyDef.position.set(MathUtils.randomFloat(xLo, xHi), MathUtils.randomFloat(yLo, yHi));
		
		Body body2 = m_world.createBody(triangleBodyDef);
		body2.createFixture(triangleShapeDef);
		
		// Small box
		polygon.setAsBox(1.0f, 0.5f);
		
		FixtureDef boxShapeDef = new FixtureDef();
		boxShapeDef.shape = polygon;
		boxShapeDef.density = 1.0f;
		
		BodyDef boxBodyDef = new BodyDef();
		boxBodyDef.type = BodyType.DYNAMIC;
		boxBodyDef.position.set(MathUtils.randomFloat(xLo, xHi), MathUtils.randomFloat(yLo, yHi));
		
		Body body3 = m_world.createBody(boxBodyDef);
		body3.createFixture(boxShapeDef);
		
		// Large box (recycle definitions)
		polygon.setAsBox(2.0f, 1.0f);
		boxBodyDef.position.set(MathUtils.randomFloat(xLo, xHi), MathUtils.randomFloat(yLo, yHi));
		
		Body body4 = m_world.createBody(boxBodyDef);
		body4.createFixture(boxShapeDef);
		
		// Small circle
		CircleShape circle = new CircleShape();
		circle.m_radius = 1.0f;
		
		FixtureDef circleShapeDef = new FixtureDef();
		circleShapeDef.shape = circle;
		circleShapeDef.density = 1.0f;
		
		BodyDef circleBodyDef = new BodyDef();
		circleBodyDef.type = BodyType.DYNAMIC;
		circleBodyDef.position.set(MathUtils.randomFloat(xLo, xHi), MathUtils.randomFloat(yLo, yHi));
		
		Body body5 = m_world.createBody(circleBodyDef);
		body5.createFixture(circleShapeDef);
		
		// Large circle
		circle.m_radius *= 2.0f;
		circleBodyDef.position.set(MathUtils.randomFloat(xLo, xHi), MathUtils.randomFloat(yLo, yHi));
		
		Body body6 = m_world.createBody(circleBodyDef);
		body6.createFixture(circleShapeDef);
	}
	
	/**
	 * @see org.jbox2d.testbed.framework.TestbedTest#step(org.jbox2d.testbed.framework.ShowcaseSettings)
	 */
	@Override
	public void step(ShowcaseSettings settings) {
		super.step(settings);
		
		// We are going to destroy some bodies according to contact
		// points. We must buffer the bodies that should be destroyed
		// because they may belong to multiple contact points.
		HashSet<Body> nuke = new HashSet<Body>();
		
		// Traverse the contact results. Destroy bodies that
		// are touching heavier bodies.
		for (int i = 0; i < m_pointCount; ++i) {
			ContactPoint point = points[i];
			
			Body body1 = point.fixtureA.getBody();
			Body body2 = point.fixtureB.getBody();
			float mass1 = body1.getMass();
			float mass2 = body2.getMass();
			
			if (mass1 > 0.0f && mass2 > 0.0f) {
				if (mass2 > mass1) {
					nuke.add(body1);
				}
				else {
					nuke.add(body2);
				}
			}
		}
		
		// Sort the nuke array to group duplicates.
		// Arrays.sort(nuke);
		
		// Destroy the bodies, skipping duplicates.
		for (Body b : nuke) {
			
			if (b != m_bomb) {
				m_world.destroyBody(b);
			}
		}
	}
	
	/**
	 * @see org.jbox2d.testbed.framework.TestbedTest#getTestName()
	 */
	@Override
	public String getTestName() {
		return "Collision Processing";
	}
	
}