Box2DFlash Hello World
Box2DFlash物理引擎的基本程序包括：b2World：b2World(gravity:b2Vec2, doSleep:Boolean)
b2BodyDef：通过物体定义来指定物体的类型(type)、初始位置(position)、角度(angle)、线速度(linearVelocity)、线速度阻尼 (linearDamping)、角速度(angularVelocity)和角速度阻尼(angularDamping)等
B2body：通过B2BodyDef在b2World中创建物体
b2PolygonShape：多边形。包括：
SetAsBox(hx:Number, hy:Number):void
SetAsOrientedBox(hx:Number,hy:Number,center:b2Vec2 = null, angle:Number = 0.0):void
SetAsArray(vertices:Array, vertexCount:Number = 0):void
b2CircleShape：圆形
b2FixtureDef：将Shape绑定到Body，指定形状的定义(shape)、密度(density)、摩擦(friction)和弹力(restitution)
它们之间的关系如下：<img class="alignnone size-large wp-image-190" title="b2world" src="http://www.everyinch.net/wp-content/uploads/2011/10/b2world-1024x666.jpg" alt="" width="725" height="471" />
定义世界：
var gravity:b2Vec2 = new b2Vec2(0.0,9.8);
var doSleep:Boolean = true;
world = new b2World(gravity,doSleep);
静态物体：
var bodyDef:b2BodyDef = new b2BodyDef();
bodyDef.position.Set(10,10);
var body:b2Body = world.CreateBody(bodyDef);
var shape:b2PolygonShape = new b2PolygonShape();
shape.SetAsBox(10,10);
body.CreateFixture2(shape);
定义动态物体：
var bodyDef:b2BodyDef = new b2BodyDef();
bodyDef.type = b2Body.b2_dynamicBody;
bodyDef.position.Set(10,10);
bodyDef.angle = Math.random()*Math.PI;
var shape:b2PolygonShape = new b2PolygonShape();
shape.SetAsBox(10,10);
var fixtureDef:b2FixtureDef = new b2FixtureDef();
fixtureDef.shape = shape;
fixtureDef.density = 1.0;
fixtureDef.friction = 0.3;
fixtureDef.restitution = 0.1;
var body:b2Body = world.CreateBody(bodyDef);
body.CreateFixture(fixtureDef);
查看完整版本： Box2DFlash Hello World
Tags: Box2DFlash