Box2D物体在碰撞时不旋转

Question

我一直在尝试学习Box2DWeb，这是一个AS版本的Box2D的JS移植。我只是试图建立一个简单的设置，其中有一个静态斜坡和一个动态的盒子落在上面。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);

你可以在jsFiddle上查看实时结果。正如你所看到的，当方块碰到斜坡时不会旋转。我做错了什么？

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/

- Alex Turpin

Answer 1

为盒子添加摩擦力和密度。 ...并不要立即离开IRC频道，有时需要超过3分钟。

- Kuukunen

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我必须离开参加一个局域网聚会，我了解IRC的复杂性。感谢你的帮助！ - Alex Turpin

只需要密度。 - eliteslayer

Answer 2

啊，你需要在落下物体的固定装置上设置摩擦力和密度，而不是物体本身。

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

顺便说一句，感谢你指引我了解Box2D - 我以前没有见过这个物理引擎，看起来很有趣 :)

- Rob Agar

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只需要调整密度就可以解决这个问题。 - iforce2d