box2d旋转关节之汽车
[code lang="as3"]package{
import Box2D.Collision.Shapes.b2CircleShape;
import Box2D.Collision.Shapes.b2PolygonShape;
import Box2D.Common.Math.b2Vec2;
import Box2D.Dynamics.Joints.b2RevoluteJoint;
import Box2D.Dynamics.Joints.b2RevoluteJointDef;
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.KeyboardEvent;
import flash.ui.Keyboard;
[SWF(width="800",height="600",frameRate="32",backgroundColor="0x000000")]
public class RevoluteJoint_Vehicle extends Sprite{
private var world:b2World;
private var timeStep:Number;
private var iterations:uint;
private var pixelsPerMeter:Number = 30;
private var frontJoint:b2RevoluteJoint;
private var rearJoint:b2RevoluteJoint;
public function RevoluteJoint_Vehicle(){
createWorld();
makeDebugDraw();
createGround();
createVehicle();
stage.addEventListener(KeyboardEvent.KEY_DOWN,onKeyDown);
addEventListener(Event.ENTER_FRAME,onEnterframe);
}
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);
world.SetDebugDraw(debugDraw);
}
private function createGround():void{
var bodyDef:b2BodyDef = new b2BodyDef();
bodyDef.position.Set(400/pixelsPerMeter,585/pixelsPerMeter);
var box:b2PolygonShape = new b2PolygonShape();
box.SetAsBox(400/pixelsPerMeter,15/pixelsPerMeter);
var fixtureDef:b2FixtureDef = new b2FixtureDef();
fixtureDef.shape = box;
fixtureDef.density = 1;
fixtureDef.friction = 1;
var body:b2Body = world.CreateBody(bodyDef);
body.CreateFixture(fixtureDef);
bodyDef.position.Set(50/pixelsPerMeter,550/pixelsPerMeter);
box.SetAsBox(50/pixelsPerMeter,50/pixelsPerMeter);
fixtureDef.shape = box;
fixtureDef.density = 1;
fixtureDef.friction = 1;
body = world.CreateBody(bodyDef);
body.CreateFixture(fixtureDef);
bodyDef.position.Set(750/pixelsPerMeter,550/pixelsPerMeter);
box.SetAsBox(50/pixelsPerMeter,50/pixelsPerMeter);
fixtureDef.shape = box;
fixtureDef.density = 1;
fixtureDef.friction = 1;
body = world.CreateBody(bodyDef);
body.CreateFixture(fixtureDef);
}
private function createVehicle():void{
var bodyDef:b2BodyDef = new b2BodyDef();
bodyDef.position.Set(250/pixelsPerMeter,35/pixelsPerMeter);
bodyDef.type = b2Body.b2_dynamicBody;
var box:b2PolygonShape = new b2PolygonShape();
box.SetAsBox(50/pixelsPerMeter,10/pixelsPerMeter);
var fixtureDef:b2FixtureDef = new b2FixtureDef();
fixtureDef.shape = box;
fixtureDef.density = 1;
fixtureDef.friction = 1;
fixtureDef.restitution = 0.1;
var body:b2Body = world.CreateBody(bodyDef);
body.CreateFixture(fixtureDef);
var circle:b2CircleShape = new b2CircleShape(20/pixelsPerMeter);
fixtureDef.shape = circle;
fixtureDef.density = 1;
fixtureDef.friction = 5;
fixtureDef.restitution = 0.1;
bodyDef.allowSleep = false;
bodyDef.position.Set(body.GetWorldCenter().x+40/pixelsPerMeter,body.GetWorldCenter().y);
var frontWheel:b2Body = world.CreateBody(bodyDef);
frontWheel.CreateFixture(fixtureDef);
bodyDef.position.Set(body.GetWorldCenter().x-40/pixelsPerMeter,body.GetWorldCenter().y);
var rearWheel:b2Body = world.CreateBody(bodyDef);
rearWheel.CreateFixture(fixtureDef);
var frontJointDef:b2RevoluteJointDef = new b2RevoluteJointDef();
frontJointDef.enableMotor = true;
frontJointDef.maxMotorTorque = 8;
frontJointDef.Initialize(body,frontWheel,frontWheel.GetWorldCenter());
frontJoint = world.CreateJoint(frontJointDef) as b2RevoluteJoint;
var rearJointDef:b2RevoluteJointDef = new b2RevoluteJointDef();
rearJointDef.enableMotor = true;
rearJointDef.maxMotorTorque = 8;
rearJointDef.Initialize(body,rearWheel,rearWheel.GetWorldCenter());
rearJoint = world.CreateJoint(rearJointDef) as b2RevoluteJoint;
}
private function onKeyDown(e:KeyboardEvent):void{
switch(e.keyCode){
case Keyboard.LEFT:
rearJoint.SetMotorSpeed(-8);
frontJoint.SetMotorSpeed(-8);
break;
case Keyboard.RIGHT:
rearJoint.SetMotorSpeed(8);
frontJoint.SetMotorSpeed(8);
break;
}
}
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/RevoluteJoint_Vehicle-300x184.jpg" alt="" title="RevoluteJoint_Vehicle" width="300" height="184" class="alignnone size-medium wp-image-358" />