DebugDraw

Box2D everyinch 2837℃ 0评论

在给Box2DFlash中的形状赋予纹理之前,缺省采用DebugDraw方式绘制形状。DebugDraw由若干标志位组成:
e_shapeBit:绘制形状轮廓
e_jointBit:绘制关节的节点和连接线
e_aabbBit:绘制轴对齐边界框(axis aligned bounding boxes)
e_controllerBit:绘制控制器
e_pairBit: 绘制宽相对
e_centerOfMassBit:绘制质量的中心
示例代码如下:

package{
import Box2D.Collision.Shapes.b2CircleShape;
import Box2D.Collision.Shapes.b2PolygonShape;
import Box2D.Collision.Shapes.b2Shape;
import Box2D.Collision.b2AABB;
import Box2D.Common.Math.b2Vec2;
import Box2D.Dynamics.Joints.b2MouseJoint;
import Box2D.Dynamics.Joints.b2MouseJointDef;
import Box2D.Dynamics.b2Body;
import Box2D.Dynamics.b2BodyDef;
import Box2D.Dynamics.b2DebugDraw;
import Box2D.Dynamics.b2Fixture;
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 DebugDraw extends Sprite{
private var world:b2World;
private var body:b2Body;
private var timeStep:Number;
private var iterations:uint;
private var pixelsPerMeter:Number = 30;
private var mouseJoint:b2MouseJoint;
private var mousePVec:b2Vec2 = new b2Vec2();

public function DebugDraw(){
createWorld();
makeDebugDraw();
createWall();
createBodies();
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 |
b2DebugDraw.e_controllerBit | b2DebugDraw.e_aabbBit |
b2DebugDraw.e_centerOfMassBit | b2DebugDraw.e_pairBit);
world.SetDebugDraw(debugDraw);
}

private function createWall():void{
var bodyDef:b2BodyDef = new b2BodyDef();
// Body的中心点
bodyDef.position.Set(400/pixelsPerMeter,585/pixelsPerMeter);
body = world.CreateBody(bodyDef);
var shape:b2PolygonShape = new b2PolygonShape();
// 几何体的半宽和半高
shape.SetAsBox(400/pixelsPerMeter,15/pixelsPerMeter);
body.CreateFixture2(shape);
}

private function createBodies():void{
for(var i:int=0;i<10;i++){ var bodyDef:b2BodyDef = new b2BodyDef(); bodyDef.type = b2Body.b2_dynamicBody; bodyDef.position.x = (Math.random()*600+120)/pixelsPerMeter; bodyDef.position.y = (Math.random()*150)/pixelsPerMeter; var hx:Number = (Math.random()*30+15)/pixelsPerMeter; var hy:Number = (Math.random()*30+15)/pixelsPerMeter; var fixtureDef:b2FixtureDef = new b2FixtureDef(); fixtureDef.density = 1.0; fixtureDef.friction = 0.5; fixtureDef.restitution = 0.2; if(Math.random()<0.5){ var square:b2PolygonShape = new b2PolygonShape(); square.SetAsBox(hx,hy); fixtureDef.shape = square; body = world.CreateBody(bodyDef); body.CreateFixture(fixtureDef); } else{ var circle:b2CircleShape = new b2CircleShape(); circle.SetRadius(hx); fixtureDef.shape = circle; body = world.CreateBody(bodyDef); body.CreateFixture(fixtureDef); } } } private function onMouseDown(e:MouseEvent):void{ var body:b2Body = getBodyAtMouse(); if(body){ // 建立MouseJoint定义 var mouseJointDef:b2MouseJointDef = new b2MouseJointDef(); // bodyA为无碰撞检测的静态刚体 mouseJointDef.bodyA = world.GetGroundBody(); // bodyB为当前检测到被点击的刚体 mouseJointDef.bodyB = body; // 设置MouseJoint的最初世界位置 mouseJointDef.target.Set(mouseX/pixelsPerMeter,mouseY/pixelsPerMeter); mouseJointDef.maxForce = 30000; mouseJoint = world.CreateJoint(mouseJointDef) as b2MouseJoint; } } private function onMouseUp(e:MouseEvent):void{ if(mouseJoint){ world.DestroyJoint(mouseJoint); mouseJoint = null; } } private function getBodyAtMouse(includeStatic:Boolean = false):b2Body{ var mouseXWorldPhys:Number = mouseX/pixelsPerMeter; var mouseYWorldPhys:Number = mouseY/pixelsPerMeter; mousePVec.Set(mouseXWorldPhys,mouseYWorldPhys); // 利用当前鼠标向量建立一个很小的b2AABB var aabb:b2AABB = new b2AABB(); aabb.lowerBound.Set(mouseXWorldPhys-0.001,mouseYWorldPhys-0.001); aabb.upperBound.Set(mouseXWorldPhys+0.001,mouseYWorldPhys+0.001); var body:b2Body = null; var fixture:b2Fixture; function GetBodyCallBack(fixture:b2Fixture):Boolean{ var shape:b2Shape = fixture.GetShape(); if(fixture.GetBody().GetType() != b2Body.b2_staticBody || includeStatic){ var inside:Boolean = shape.TestPoint(fixture.GetBody().GetTransform(),mousePVec); if(inside){ body = fixture.GetBody(); return false; } } return true; } // 在World中查找与鼠标向量定义的Shape相重叠的Shape world.QueryAABB(GetBodyCallBack,aabb); return body; } private function onEnterframe(e:Event):void{ world.Step(timeStep,iterations,iterations); world.ClearForces(); world.DrawDebugData(); if(mouseJoint){ var xpos:Number = mouseX/pixelsPerMeter; var ypos:Number = mouseY/pixelsPerMeter; var v2:b2Vec2 = new b2Vec2(xpos,ypos); mouseJoint.SetTarget(v2); } } } } [/code]



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