box2d实时绘制圆形方法之二：更贴近圆形的边界
[code lang="as3"]package{
import Box2D.Collision.Shapes.b2CircleShape;
import Box2D.Collision.Shapes.b2PolygonShape;
import Box2D.Common.Math.b2Vec2;
import Box2D.Dynamics.b2Body;
import Box2D.Dynamics.b2BodyDef;
import Box2D.Dynamics.b2DebugDraw;
import Box2D.Dynamics.b2FixtureDef;
import Box2D.Dynamics.b2World;
import flash.display.Sprite;
import flash.events.Event;
import flash.events.MouseEvent;
[SWF(width="800",height="600",frameRate="32",backgroundColor="0x000000")]
public class DrawCircle2 extends Sprite{
private var world:b2World;
private var timeStep:Number;
private var iterations:uint;
private var pixelsPerMeter:Number = 30;
private var initX:Number = 0.0;
private var initY:Number = 0.0;
private var drawing:Boolean = false;
public function DrawCircle2(){
createWorld();
makeDebugDraw();
addGround(400/pixelsPerMeter,585/pixelsPerMeter,400/pixelsPerMeter,15/pixelsPerMeter);
addEventListener(Event.ENTER_FRAME,onEnterframe);
stage.addEventListener(MouseEvent.MOUSE_DOWN,onMouseDown);
stage.addEventListener(MouseEvent.MOUSE_UP,onMouseUp);
}
private function createWorld():void{
var gravity:b2Vec2 = new b2Vec2(0.0,9.8);
var doSleep:Boolean = true;
world = new b2World(gravity,doSleep);
world.SetWarmStarting(true);
timeStep = 1.0/30.0;
iterations = 10;
}
private function makeDebugDraw():void{
var debugDraw:b2DebugDraw = new b2DebugDraw();
var debugSprite:Sprite = new Sprite();
addChild(debugSprite);
debugDraw.SetSprite(debugSprite);
debugDraw.SetDrawScale(30.0);
debugDraw.SetFillAlpha(0.5);
debugDraw.SetLineThickness(1.0);
debugDraw.SetFlags(b2DebugDraw.e_shapeBit | b2DebugDraw.e_jointBit);
world.SetDebugDraw(debugDraw);
}
private function addGround(x:Number,y:Number,hx:Number,hy:Number):void{
var bodyDef:b2BodyDef = new b2BodyDef();
bodyDef.position.Set(x,y);
var body:b2Body = world.CreateBody(bodyDef);
var shape:b2PolygonShape = new b2PolygonShape();
shape.SetAsBox(hx,hy);
body.CreateFixture2(shape);
}
private function onMouseDown(e:MouseEvent):void{
initX = e.localX;
initY = e.localY;
drawing = true;
stage.addEventListener(MouseEvent.MOUSE_MOVE,onMouseMove);
}
private function onMouseMove(e:MouseEvent):void{
if(drawing){
graphics.clear();
graphics.beginFill(0xFF0000,0.5);
var radius:Number = Math.sqrt((e.localX-initX)*(e.localX-initX)+(e.localY-initY)*(e.localY-initY));
graphics.drawCircle(initX,initY,radius);
}
}
private function onMouseUp(e:MouseEvent):void{
graphics.clear();
drawing = false;
var finalX:Number = e.localX;
var finalY:Number = e.localY;
var radius:Number = Math.sqrt((e.localX-initX)*(e.localX-initX)+(e.localY-initY)*(e.localY-initY));
if(radius > 0){
addCircle(initX/pixelsPerMeter,initY/pixelsPerMeter,radius/pixelsPerMeter);
}
}
private function addCircle(x:Number,y:Number,radius:Number):void{
var bodyDef:b2BodyDef = new b2BodyDef();
bodyDef.type = b2Body.b2_dynamicBody;
bodyDef.position.Set(x,y);
var circle:b2CircleShape = new b2CircleShape();
circle.SetRadius(radius);
var fixtureDef:b2FixtureDef = new b2FixtureDef();
fixtureDef.shape = circle;
fixtureDef.density = 1.0;
fixtureDef.friction = 0.3;
fixtureDef.restitution = 0.2;
var body:b2Body = world.CreateBody(bodyDef);
body.CreateFixture(fixtureDef);
}
private function onEnterframe(e:Event):void{
world.Step(timeStep,iterations,iterations);
world.ClearForces();
world.DrawDebugData();
}
}
}
[/code]
<img src="http://www.everyinch.net/wp-content/uploads/2011/10/drawCircle2-300x225.jpg" alt="" title="drawCircle2" width="300" height="225" class="alignnone size-medium wp-image-333" />