我正在努力创造一个只能在斜坡上冲浪的滑雪板。但是当我运行项目时，我添加的资产运行速度比它的父体更快。它刚刚用完了b2Body的界限。为什么即使在相对于它的父b2body设置其位置之后也会发生这种情况。这是我使用的代码。更不用说我是Box2d的新手了。
package {
import flash.display.MovieClip;
import flash.display.Sprite;
import Box2D.Collision.*;
import Box2D.Common.*;
import Box2D.Dynamics.*;
import Box2D.Dynamics.Joints.*;
import Box2D.Dynamics.Contacts.*;
import Box2D.Common.Math.*;
import Box2D.Collision.Shapes.*;
import flash.events.Event;
import flash.events.KeyboardEvent;
import flash.sampler.NewObjectSample;
import flash.display.Shape;
public class PhysSnowboarder extends Sprite {
//Degree to Radian Constant
private const degreesToRadians:Number=0.0174532925;
//World Definition
public var worldScale:Number=30;
private var world:b2World= new b2World(new b2Vec2(0,9.8),true);
//Key Flags (Game Control Keys)
private var left:Boolean=false;
private var right:Boolean=false;
//Hill attributes and misc
private var nextHill:Number=240;
private var realHeight:Number=240;
private var realWidth:Number=0;
private var buildNextHillAt:Number=0;
//Sphere
var theSphere:b2Body;
var riderBody:b2Body;
//Game Canvas
private var gameCanvas:Sprite= new Sprite();
public function PhysSnowboarder(){
// i created a simple image of a snowboarder, created an as linkage.
// Inherits flash.display.sprite
var boardRider:BoardRider= new BoardRider();
//create a sphere
var sphereShape:b2CircleShape= new b2CircleShape(50/worldScale);
var sphereFixture:b2FixtureDef= new b2FixtureDef();
sphereFixture.density=2;
sphereFixture.friction=3;
sphereFixture.restitution=0.1;
//sphereFixture.filter.groupIndex=-1;
sphereFixture.shape=sphereShape;
//sphere body
var sphereBodyDef:b2BodyDef= new b2BodyDef();
sphereBodyDef.type=b2Body.b2_dynamicBody;
sphereBodyDef.position.Set(320/worldScale,0);
sphereBodyDef.userData=new Object();
sphereBodyDef.userData.asset=boardRider;
//Add the sphere to stage
theSphere=world.CreateBody(sphereBodyDef);
theSphere.SetUserData(sphereBodyDef.userData);
theSphere.CreateFixture(sphereFixture);
addChild(sphereBodyDef.userData.asset);
//theSphere.SetUserData(boardRider);
//addChild(theSphere.GetUserData());
addChild(gameCanvas);
//stage.addChild(new ());
debugDraw();
while(realWidth<1280){
nextHill=drawHill(5,realWidth,nextHill);
}
addEventListener(Event.ENTER_FRAME,updateWorld);
stage.addEventListener(KeyboardEvent.KEY_DOWN,keyPressed);
stage.addEventListener(KeyboardEvent.KEY_UP,keyReleased);
}
//debugDraw
private function debugDraw():void{
var worldDebugDraw:b2DebugDraw= new b2DebugDraw();
var debugSprite:Sprite= new Sprite();
gameCanvas.addChild(debugSprite);
worldDebugDraw.SetSprite(debugSprite);
worldDebugDraw.SetDrawScale(worldScale);
worldDebugDraw.SetFlags(b2DebugDraw.e_shapeBit|b2DebugDraw.e_jointBit);
worldDebugDraw.SetFillAlpha(0.5);
world.SetDebugDraw(worldDebugDraw);
}
//drawHill
private function drawHill(pixelStep:int,xOffset:Number,yOffset:Number):Number{
var hillStartY:Number=yOffset;
var hillWidth:Number=120+Math.ceil(Math.random()*26)*20;
realWidth+=hillWidth;
var numberOfSlices=hillWidth/pixelStep;
var hillVector:Vector.<b2Vec2>;
var randomHeight:Number;
if(xOffset==0){
randomHeight=0;
}
else{
do{
//randomHeight=Math.random()*hillWidth/7.5;
randomHeight=240/worldScale;
}while(realHeight+randomHeight>600);
}
realHeight+=randomHeight;
hillStartY-=randomHeight;
for (var j:int=0; j<numberOfSlices/2; j++) {
hillVector=new Vector.<b2Vec2>();
hillVector.push(new b2Vec2((j*pixelStep+xOffset)/worldScale,480/worldScale));
hillVector.push(new b2Vec2((j*pixelStep+xOffset)/worldScale,(hillStartY+randomHeight*Math.cos(2*Math.PI/numberOfSlices*j))/worldScale));
hillVector.push(new b2Vec2(((j+1)*pixelStep+xOffset)/worldScale,(hillStartY+randomHeight*Math.cos(2*Math.PI/numberOfSlices*(j+1)))/worldScale));
hillVector.push(new b2Vec2(((j+1)*pixelStep+xOffset)/worldScale,480/worldScale));
var sliceBody:b2BodyDef=new b2BodyDef ;
var centre:b2Vec2=findCentroid(hillVector,hillVector.length);
sliceBody.position.Set(centre.x,centre.y);
for (var z:int=0; z<hillVector.length; z++) {
hillVector[z].Subtract(centre);
}
var slicePoly:b2PolygonShape=new b2PolygonShape ;
slicePoly.SetAsVector(hillVector,4);
var sliceFixture:b2FixtureDef=new b2FixtureDef ;
sliceFixture.shape=slicePoly;
var worldSlice:b2Body=world.CreateBody(sliceBody);
worldSlice.CreateFixture(sliceFixture);
}
hillStartY-=randomHeight;
if (xOffset==0) {
randomHeight=0;
}
else {
do {
randomHeight=Math.random()*hillWidth/5;
} while (realHeight-randomHeight<240);
}
realHeight-=randomHeight;
hillStartY+=randomHeight;
for (j=numberOfSlices/2; j<numberOfSlices; j++) {
hillVector=new Vector.<b2Vec2>();
hillVector.push(new b2Vec2((j*pixelStep+xOffset)/worldScale,480/worldScale));
hillVector.push(new b2Vec2((j*pixelStep+xOffset)/worldScale,(hillStartY+randomHeight*Math.cos(2*Math.PI/numberOfSlices*j))/worldScale));
hillVector.push(new b2Vec2(((j+1)*pixelStep+xOffset)/worldScale,(hillStartY+randomHeight*Math.cos(2*Math.PI/numberOfSlices*(j+1)))/worldScale));
hillVector.push(new b2Vec2(((j+1)*pixelStep+xOffset)/worldScale,480/worldScale));
sliceBody=new b2BodyDef ;
centre=findCentroid(hillVector,hillVector.length);
sliceBody.position.Set(centre.x,centre.y);
for (z=0; z<hillVector.length; z++) {
hillVector[z].Subtract(centre);
}
slicePoly=new b2PolygonShape ;
slicePoly.SetAsVector(hillVector,4);
sliceFixture=new b2FixtureDef ;
sliceFixture.shape=slicePoly;
worldSlice=world.CreateBody(sliceBody);
worldSlice.CreateFixture(sliceFixture);
}
hillStartY=hillStartY+randomHeight;
return (hillStartY);
}
//findCentroid
private function findCentroid(vs:Vector.<b2Vec2>,count:uint):b2Vec2{
var c:b2Vec2= new b2Vec2();
var area:Number=0.0;
var p1X:Number=0.0;
var p1Y:Number=0.0;
var inv3:Number=1.0/3.0;
for(var i:int=0; i<count;++i){
var p2:b2Vec2=vs[i];
var p3:b2Vec2=i+1<count?vs[int(i+1)]:vs[0];
var e1X:Number=p2.x-p1X;
var e1Y:Number=p2.y-p1Y;
var e2X:Number=p3.x-p1X;
var e2Y:Number=p3.y-p1Y;
var D:Number=(e1X*e2Y-e1Y*e2X);
var triangleArea:Number=0.5*D;
area+=triangleArea;
c.x+=triangleArea*inv3*(p1X+p2.x+p3.x);
c.y+=triangleArea*inv3*(p1Y+p2.y+p3.y);
}
c.x*=1.0/area;
c.y*=1.0/area;
return c;
}
//updateWorld
private function updateWorld(e:Event):void{
if(left)
{
//theSphere.SetLinearVelocity(new b2Vec2(-10,0));
theSphere.ApplyTorque(-3);
}
if(right)
{
//theSphere.SetLinearVelocity(new b2Vec2(10,0));
theSphere.ApplyTorque(3);
//theSphere.ApplyTorque(0.5);
}
world.Step(1/30,10,10);
world.ClearForces();
for(var currentBody:b2Body=world.GetBodyList(); currentBody; currentBody=currentBody.GetNext())
{
if(currentBody.GetUserData()!=null){
gameCanvas.x=320-currentBody.GetPosition().x*worldScale;
gameCanvas.y=240-currentBody.GetPosition().y*worldScale;
//gameCanvas.addChild(currentBody.GetUserData());
if(gameCanvas.x<=-realWidth+800){
nextHill=drawHill(5,realWidth,nextHill);
}
//This is where i set the position of the of the asset i created.
currentBody.GetUserData().asset.x=(currentBody.GetPosition().x*worldScale);
currentBody.GetUserData().asset.y=((currentBody.GetPosition().y+(50/worldScale))*worldScale);
}
if(currentBody.GetPosition().x*worldScale<(gameCanvas.x*-1)-640){
world.DestroyBody(currentBody);
}
}
world.DrawDebugData();
}
//keyPressed
private function keyPressed(e:KeyboardEvent):void {
switch (e.keyCode) {
case 37 :
left=true;
break;
case 39 :
right=true;
break;
}
}
//keyReleased
private function keyReleased(e:KeyboardEvent):void {
switch (e.keyCode) {
case 37 :
left=false;
break;
case 39 :
right=false;
break;
}
}
}//Class Ends here
}//Package Ends here