物理模拟引擎box2D-2
根据第一例子重新自己做了box2D的例子，感觉写这个比前面的体会多点。
package {import Box2D.Collision.b2AABB;import Box2D.Collision.Shapes.b2PolygonDef;import Box2D.Collision.Shapes.b2ShapeDef;import Box2D.Common.Math.b2Vec2;import Box2D.Dynamics.b2Body;import Box2D.Dynamics.b2BodyDef;import Box2D.Dynamics.b2DebugDraw;import Box2D.Dynamics.b2World;import flash.display.MovieClip;import flash.display.Sprite;import flash.events.Event;/** * ... * @author ottoliu */public class Hello extends MovieClip {protected var _world:b2World;// the ratio of pixels to meterspublic const RATIO:Number = 40;private var _fallingBody:b2Body;public function Hello() {// 1. setup the world setupWorld();// 2. Creating the wall and floorcreateWallAndFloor();// 3 . adding the crateaddCrate();setupDebugDraw();addEventListener(Event.ENTER_FRAME, newFrameEvent);}private function setupDebugDraw():void{var spriteToDraw:Sprite = new Sprite();addChild(spriteToDraw);var artistForHire:b2DebugDraw = new b2DebugDraw();artistForHire.m_sprite = spriteToDraw;artistForHire.m_drawScale = RATIO;artistForHire.SetFlags(b2DebugDraw.e_shapeBit);artistForHire.m_fillAlpha = 0.6;artistForHire.m_lineThickness = 2.0;_world.SetDebugDraw(artistForHire);}private function newFrameEvent(e:Event):void {_world.Step(1.0 / 30.0, 10);trace("falling crate is "+_fallingBody.GetPosition().x+" , "+_fallingBody.GetPosition().y);}private function addCrate():void{//falling blocks to the world var fallingCrateDef:b2PolygonDef = new b2PolygonDef(); fallingCrateDef.SetAsBox(25 / RATIO, 25 / RATIO); fallingCrateDef.friction = 0.3; fallingCrateDef.restitution = 0.1; fallingCrateDef.density = 0.4; //set it to 250,-30var fallingBodyDef:b2BodyDef = new b2BodyDef();fallingBodyDef.position.Set(250 / RATIO, -50 / RATIO);fallingBodyDef.angle = 30 * Math.PI / 180;_fallingBody = _world.CreateBody(fallingBodyDef);_fallingBody.CreateShape(fallingCrateDef);_fallingBody.SetMassFromShapes();}private function createWallAndFloor():void{//create the shape definationvar bigLongPolyDef:b2PolygonDef = new b2PolygonDef();bigLongPolyDef.vertexCount = 4;b2Vec2(bigLongPolyDef.vertices[0].Set(0 / RATIO, 0 / RATIO));b2Vec2(bigLongPolyDef.vertices[1].Set(550 / RATIO, 0 / RATIO));b2Vec2(bigLongPolyDef.vertices[2].Set(550 / RATIO, 10 / RATIO));b2Vec2(bigLongPolyDef.vertices[3].Set(0 / RATIO, 10 / RATIO));bigLongPolyDef.friction = 0.5;bigLongPolyDef.restitution = 0.3;bigLongPolyDef.density = 0.0;// create the body definationvar floorBodyDef:b2BodyDef = new b2BodyDef();floorBodyDef.position.Set(0 / RATIO, 390 / RATIO );// create bodyvar floorBody:b2Body = _world.CreateBody(floorBodyDef);// create shapefloorBody.CreateShape(bigLongPolyDef);floorBody.SetMassFromShapes();//wallvar tallskinDef:b2PolygonDef = new b2PolygonDef();tallskinDef.SetAsBox(5 / RATIO, 195 / RATIO);tallskinDef.friction = 0.5;tallskinDef.restitution = 0.3;tallskinDef.density = 0.0;var wallBodyDef:b2BodyDef = new b2BodyDef();wallBodyDef.position.Set(5 / RATIO, 195 / RATIO);var leftWall:b2Body = _world.CreateBody(wallBodyDef);leftWall.CreateShape(tallskinDef);leftWall.SetMassFromShapes();wallBodyDef.position.Set(545 / RATIO, 195 / RATIO );var rightWall:b2Body = _world.CreateBody(wallBodyDef);rightWall.CreateShape(tallskinDef);rightWall.SetMassFromShapes();trace("the world has "+_world.GetBodyCount()+" bodies.");}private function setupWorld():void{// 1. setup the size of the universevar universeSize:b2AABB = new b2AABB();universeSize.lowerBound.Set( -3000/RATIO, -3000/RATIO);universeSize.upperBound.Set( 3000/RATIO, 3000/RATIO);// 2. define gravityvar gravity:b2Vec2= new b2Vec2(0.0, 10.0);// 3. ignore sleeping?var doSleep:Boolean = true;_world = new b2World(universeSize, gravity, doSleep);trace("my world has " + _world.GetBodyCount() + "bodies.");}}}