Question

我想我的看似简单的问题有一个简单的答案，但我可能完全错了。无论如何，我是box2dWeb的新手，在我的Box2dWeb世界中，我创建了一个地板和一个简单的坠落物体。当我“调试绘制”到我的画布时，我看到盒子掉落了一切。我想要做的就是将我创建的下降对象的x位置输出到browser console.log中，它不能正常工作。 console.log只显示我的对象的起始位置，但即使画布中的对象正在下降，该数字也不会更新。经过几个小时的搜索引擎搜索，以及Seth Ladds教程之类的地方我都空了。我希望有人可以提供帮助。我提供了一些示例代码来帮助自己解释一下。希望能帮助到你。感谢所有回复的人。

  var world;

  function init() {
     var b2Vec2 = Box2D.Common.Math.b2Vec2
      , b2BodyDef = Box2D.Dynamics.b2BodyDef
      , b2Body = Box2D.Dynamics.b2Body
      , b2FixtureDef = Box2D.Dynamics.b2FixtureDef
      , b2Fixture = Box2D.Dynamics.b2Fixture
      , b2World = Box2D.Dynamics.b2World
      , b2MassData = Box2D.Collision.Shapes.b2MassData
      , b2PolygonShape = Box2D.Collision.Shapes.b2PolygonShape
      , b2CircleShape = Box2D.Collision.Shapes.b2CircleShape
      , b2DebugDraw = Box2D.Dynamics.b2DebugDraw
        ;

     world = new b2World(
           new b2Vec2(0, 10) //gravity
        , true //allow sleep
     );

     var fixDef = new b2FixtureDef;
     fixDef.density = 1.0;
     fixDef.friction = 0.5;
     fixDef.restitution = 0.2;

     var bodyDef = new b2BodyDef;

     //create ground
     bodyDef.type = b2Body.b2_staticBody;
     bodyDef.position.x = 9;
     bodyDef.position.y = 13;
     fixDef.shape = new b2PolygonShape;
     fixDef.shape.SetAsBox(10, 0.5);
     world.CreateBody(bodyDef).CreateFixture(fixDef);


        //FIXTURE - define fixture
        crateFixture = new b2FixtureDef;


            //set object attributes
            crateFixture.density = 0.9;
            crateFixture.friction = 0.5;
            crateFixture.restitution = 0.5;


        //BODY - define body  
        crateDef = new b2BodyDef;


            //setup type
            crateDef.type = b2Body.b2_dynamicBody;
            crateDef.position.x = 5;        
            crateDef.position.y = 5;    
            crateDef.angle = 65;


        //SHAPE - define shape
        crateFixture.shape = new b2PolygonShape;


        //define shape
            crateFixture.shape.SetAsBox(2, 2);


        //add to our world
        world.CreateBody(crateDef).CreateFixture(crateFixture);


            //setup debug draw
            var debugDraw = new b2DebugDraw();
    debugDraw.SetSprite(document.getElementById("canvas").getContext("2d"));
    debugDraw.SetDrawScale(30.0);
    debugDraw.SetFillAlpha(0.3);
    debugDraw.SetLineThickness(1.0);
    debugDraw.SetFlags(b2DebugDraw.e_shapeBit | b2DebugDraw.e_jointBit);
    world.SetDebugDraw(debugDraw);

     window.setInterval(update, 1000 / 60);
  };

  function update() {
     world.Step(
           1 / 60 //frame-rate
        , 10 //velocity iterations
        , 10 //position iterations
     );
     world.DrawDebugData();
     world.ClearForces();
     console.log('the crate is located at ' + crateDef.position.x); //position of crate doesnt update
  };

Answer 1

好的，所以不，谢谢你没有专门针对Box2DWeb的任何真实文档，我终于想到了这一点。我很快也想感谢Jer In Chicago的回复，谢谢兄弟。无论如何答案：

将对象添加到您的世界后，就像这样：

crateFixture = world.CreateBody(crateBodyDef).CreateFixture(crateFixtureDef);

您可以按如下方式获取对象的值（在我的情况下是crateBody）：

console.log('crate X: ' + crateFixture.GetBody().GetPosition().x);
console.log('crate Y: ' + crateFixture.GetBody().GetPosition().y);
console.log('crate Angle: ' + crateFixture.GetBody().GetAngle());

希望这有助于其他人！

Answer 2

好吧，找不到Box2dWeb的api / doc，所以我下载了源代码并确认了正文应该有一个位置...而不是试图使用crateBody var，让我们循环遍历所有的机构在世上，看看我们是否可以打印他们的坐标...祝你好运！

修改：试试这个

// Add after world step call
for (b = world.GetBodyList(); b; b = b.GetNext()) {
    console.log('the object is located at (' + b.position.x + ',' + b.position.y + ')');
}

Answer 3

var body = world.CreateBody(bodyDef);
body.CreateFixture(fixDef);

console.log(body.GetWorldCenter().x);

或

var body = world.CreateBody(bodyDef);
body.CreateFixture(fixDef);

console.log(body.GetPosition().x);

或

var body = world.CreateBody(bodyDef);
body.CreateFixture(fixDef);

console.log(body.GetWorldPoint(new b2Vec2(0,0)).x);

其中（0,0）是本地坐标中身体中心的坐标。 GetWorldPoint函数将其转换为世界坐标。

Answer 4

我在使用Box2dWeb时遇到了类似的问题。感谢您发布此问题。使用@JerinChicago提示我找到了解决方案。

 for (var b = world.GetBodyList() ; b; b = b.GetNext()) {
     console.log('the object is located at (' + b.GetPosition().x + ',' + b.GetPosition().y + ')');
 }

我希望这会有所帮助。

Box2dWeb中有没有办法将对象的position.x输出到console.log（）？

4 个答案: