Box2D 身体在碰撞时不旋转

Question

我一直在尝试进入Box2DWeb ，它是 Box2D 的 AS 端口的 JS 端口。 只是想在有 static 坡道和落在其上的动态框的地方进行简单的设置。 这是我的代码：

var b2World =  Box2D.Dynamics.b2World;
var b2DebugDraw = Box2D.Dynamics.b2DebugDraw;
var b2Vec2 = Box2D.Common.Math.b2Vec2;
var b2BodyDef = Box2D.Dynamics.b2BodyDef;
var b2Body = Box2D.Dynamics.b2Body;
var b2FixtureDef = Box2D.Dynamics.b2FixtureDef;
var b2PolygonShape = Box2D.Collision.Shapes.b2PolygonShape;
var b2CircleShape = Box2D.Collision.Shapes.b2CircleShape;

var width = 8;
var height = 4;

var world = new b2World(new b2Vec2(0, 10), true);

var debugDraw = new b2DebugDraw();
debugDraw.SetSprite(document.getElementById("canvas").getContext("2d"));
debugDraw.SetDrawScale(100); //Arena is 8 meters by 4 meters
debugDraw.SetFillAlpha(0.5);
debugDraw.SetLineThickness(1);
debugDraw.SetFlags(b2DebugDraw.e_shapeBit);
world.SetDebugDraw(debugDraw);

var bodyDef = new b2BodyDef();
bodyDef.type = b2Body.b2_staticBody;
bodyDef.position.Set(3.5, 3)
var body = world.CreateBody(bodyDef);
body.SetAngle(Math.PI / 4);
var shape = new b2PolygonShape();
shape.SetAsBox(1, 0.25);
var fixtureDef = new b2FixtureDef();
fixtureDef.shape = shape;
fixtureDef.density = 1;
fixtureDef.friction = 0.3;
body.CreateFixture(fixtureDef);

var bodyDef = new b2BodyDef();
bodyDef.type = b2Body.b2_dynamicBody;
bodyDef.position.Set(3.5, 1)
var body = world.CreateBody(bodyDef);
var shape = new b2PolygonShape();
shape.SetAsBox(0.10, 0.10);
var fixtureDef = new b2FixtureDef();
fixtureDef.shape = shape;
body.CreateFixture(fixtureDef); 

setInterval(function() {
    world.Step(1 / 60, 10, 10);
    world.DrawDebugData();
    world.ClearForces();
    console.log(body.GetAngle());
}, 1000 / 60);

您可以在 jsFiddle 上看到实时结果。 如您所见，盒子在撞到坡道时不会旋转。 我究竟做错了什么？

谢谢。

一些资源：

• AS3 手册： http://www.box2dflash.org/docs/2.0.2/manual
• AS3 参考： http://www.box2dflash.org/docs/2.0.2/reference/

Answer 1

给盒子增加摩擦力和密度。 ...并且不要立即离开irc频道，有时需要3分钟以上。

Answer 2

啊，你必须在下落物体的夹具上设置摩擦和密度，而不是身体。

var fixtureDef = new b2FixtureDef();
fixtureDef.shape = shape;
fixtureDef.friction = 0.3
fixtureDef.density = 1   
body.CreateFixture(fixtureDef);

顺便说一句，感谢您为我指出 Box2D 的方向 - 我以前没见过那个物理引擎，看起来很有趣:)