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我正在创建一堆随机对象并将它们约束到一个带有棱柱关节的固定体（圆）。目标是让他们滑向那个固定的圆圈。

问题是 - 物体从关节边缘掉落，因为它们似乎没有锚定。

我究竟做错了什么？

js小提琴：http: //jsfiddle.net/Jk5VD/7/

js：（联合代码直接去Physics.prototype.connectToCenterWithJoint）

var Physics = (function () {
    function Physics() {
        this.bodies = [];
        this.testObjectCount = 30;
        this.w = new Box2D.Dynamics.b2World(new Box2D.Common.Math.b2Vec2(0, 10), true);
        var fixture = new Box2D.Dynamics.b2FixtureDef();
        this.bodyDef = new Box2D.Dynamics.b2BodyDef();
        this.bodyDef.type = Box2D.Dynamics.b2Body.b2_staticBody;
        this.bodyDef.position.x = 9;
        this.bodyDef.position.y = 13;
        fixture.shape = Box2D.Collision.Shapes.b2PolygonShape.AsBox(10, .5);
        this.w.CreateBody(this.bodyDef).CreateFixture(fixture);
        this.bodyDef.type = Box2D.Dynamics.b2Body.b2_dynamicBody;
        this.bodyDef = new Box2D.Dynamics.b2BodyDef();
        this.bodyDef.type = Box2D.Dynamics.b2Body.b2_staticBody;
        this.bodyDef.position.x = 10;
        this.bodyDef.position.y = 6;
        fixture.shape = new Box2D.Collision.Shapes.b2CircleShape(1);
        var circle = this.w.CreateBody(this.bodyDef);
        circle.CreateFixture(fixture);
        this.c = circle;
        this.bodyDef.type = Box2D.Dynamics.b2Body.b2_dynamicBody;
        this.populate();
        this.testJoints();
    }
    Physics.prototype.populate = function () {
        var fixture = new Box2D.Dynamics.b2FixtureDef();
        for(var i = 0; i < this.testObjectCount; ++i) {
            var rnd = Math.random();
            if(rnd > 0.7) {
                fixture.shape = Box2D.Collision.Shapes.b2PolygonShape.AsBox(Math.random() + 0.1, Math.random() + 0.1);
            } else if(rnd < .7 && rnd > .3) {
                fixture.shape = new Box2D.Collision.Shapes.b2CircleShape(Math.random() + 0.1);
            } else {
                var vertices = [
                    new Box2D.Common.Math.b2Vec2(0.0, 0.0), 
                    new Box2D.Common.Math.b2Vec2(1.0, 0.0), 
                    new Box2D.Common.Math.b2Vec2(0.0, 1.0)
                ];
                fixture.shape = Box2D.Collision.Shapes.b2PolygonShape.AsArray(vertices);
            }
            this.bodyDef.position.x = Math.random() * 20;
            this.bodyDef.position.y = Math.random() * 10;
            var body = this.w.CreateBody(this.bodyDef);
            body.CreateFixture(fixture);
            this.bodies.push(body);
        }
    };
    Physics.prototype.bindToCanvas = function (canvasId) {
        var _this = this;
        var debugDraw = new Box2D.Dynamics.b2DebugDraw();
        debugDraw.SetSprite((document.getElementById(canvasId)).getContext("2d"));
        debugDraw.SetDrawScale(30.0);
        debugDraw.SetFillAlpha(0.3);
        debugDraw.SetLineThickness(1.0);
        debugDraw.SetFlags(Box2D.Dynamics.b2DebugDraw.e_shapeBit | Box2D.Dynamics.b2DebugDraw.e_jointBit);
        this.w.SetDebugDraw(debugDraw);
        window.setInterval(function () {
            _this.update();
        }, 1000 / 60);
    };
    Physics.prototype.connectToCenterWithJoint = function (b) {
        var jd = new Box2D.Dynamics.Joints.b2PrismaticJointDef();
        var axis = Box2D.Common.Math.b2Math.SubtractVV(b.GetWorldCenter(), this.c.GetWorldCenter());
        axis.Normalize();
        jd.Initialize(this.c, b, b.GetWorldCenter(), axis);
        jd.lowerTranslation = -1;
        jd.upperTranslation = 0;
        jd.enableLimit = true;
        this.w.CreateJoint(jd);
    };
    Physics.prototype.testJoints = function () {
        for(var i = 0; i < this.testObjectCount; ++i) {
            this.connectToCenterWithJoint(this.bodies[i]);
        }
    };
    Physics.prototype.applyTestFoce = function () {
        for(var i = 0; i < this.testObjectCount; ++i) {
            this.bodies[i].ApplyForce(new Box2D.Common.Math.b2Vec2(5000, 0), this.bodies[i].GetWorldCenter());
        }
    };
    Physics.prototype.update = function () {
        this.w.Step(1 / 60, 10, 10);
        this.w.DrawDebugData();
        this.w.ClearForces();
    };
    return Physics;
})();
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1 回答 1

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问题是需要设置密度才能使棱柱接头起作用。这将教会我相信默认值。

使固定：

fixture.density = .5;

在这里工作：http: //jsfiddle.net/Jk5VD/9/

于 2013-03-27T17:15:27.520 回答