如何正确删除版本为Box2dWeb-2.1.a.3、Box2D_v2.3.1r3的box2d主体？ Box2D 错误？

2023-12-01

Update

自从发现问题后，我还发现 Box2D for web 到处都有泄漏：/

为了展示这一点，我做了一个在静态多边形中移动的简单圆圈，这是一段时间后的结果。

enter image description here

请注意以下项目是如何泄漏的，因为我没有创建任何主体或以任何方式改变世界：

b2Vec2
Features
b2流形点
b2联系人ID
b2歧管
b2ContactEdge
b2PolyAndCircleContact
Array
...

原帖

我遇到了问题，因为我正在分析我的游戏，而垃圾收集器不会删除我的身体、联系人和其他内容。然后我查看了他们从 GC 中保留了什么，即 Box2D 本身。这可能会导致两个选择：我做得不好或 Box2D 泄漏。我认为是我的原因。

到底是什么在保留它？

contact.m_nodeA.other 似乎是最常用于防止 GC 的。
其他时间：接触中的 m_fixtureB...参见图片

enter image description here

你可以看到body有一个__destroyed属性。这是在使用 world.DestroyBody(body) 删除它之前手动设置的

当我摧毁一个物体时，我会在调用世界上的步骤方法后调用它。

正如您从 box2d 方法中看到的那样，它没有删除另一个变量，也没有将其更改为另一个主体，并且我的主体不是 GC。

知道我在这里缺少什么吗？

现在，只有在 world.Step 未运行的情况下我才能解决问题：

var gravity = new Box2D.Vec2(0, 0);
var doSleep = true;
var world = new Box2D.World(gravity, doSleep);
var step = false;

var fixtureDef = new Box2D.FixtureDef();
fixtureDef.density = 1.0;
fixtureDef.friction = 0.5;
fixtureDef.restitution = 0.2;
fixtureDef.shape = new Box2D.PolygonShape();
fixtureDef.shape.SetAsBox(1, 1);
var bodyDef = new Box2D.BodyDef;
bodyDef.type = Box2D.Body.b2_dynamicBody;
bodyDef.position.x = 0.4;
bodyDef.position.y = 0.4;

var bodies = []
var fix = [];
window.c = function(){
    for(var i = 0; i < 100; i++){
        var body = world.CreateBody(bodyDef);
        body._id = i;

        fix.push(body.CreateFixture(fixtureDef));
        bodies.push(body);

    }
    if(step){world.Step(1/60, 3, 3); world.ClearForces();}
    console.log('Created', bodies)
    fixtureDef = null;
    bodyDef = null;
}

window.d = function(){
    _.each(bodies, function(body, i){
        body.DestroyFixture(fix[i]);
        world.DestroyBody(body);

        fix[i] = null;
        bodies[i] = null;
    })
    if(step){world.Step(1/60, 3, 3); world.ClearForces();}
    bodies = null;
    fix = null;
}

将步骤改为true，内存泄漏问题又出现了。

重现内存泄漏问题：

文件中的代码：

var gravity = new Box2D.Vec2(0, 0);
var doSleep = true;
var world = new Box2D.World(gravity, doSleep);

var bodies = []
window.c = function(){
    for(var i = 0; i < 100; i++){
        var bodyDef = new Box2D.BodyDef();
        bodyDef.type = 2;

        var shape = new Box2D.PolygonShape();
        shape.SetAsBox(1, 1);

        var fixtureDef   = new Box2D.FixtureDef();
        fixtureDef.shape = shape;
        var body = world.CreateBody(bodyDef);
        body._id = i;
        body.CreateFixture(fixtureDef);
        bodies.push(body);
    }
    world.Step(0.3, 3, 3);
    console.log('Created', bodies)
}
window.d = function(){
    _.each(bodies, function(body, i){
        world.DestroyBody(body);
        bodies[i] = null;
    })
    world.Step(0.3, 3, 3);
    bodies = null;
}

打开谷歌浏览器：

然后打开您的个人资料并制作快照。
现在在控制台中运行 c() 方法来创建 100 个实体
现在快照2
在快照中搜索 b2Body，您会发现 100 个对象数
现在运行 d() 删除你所有的身体；
通过单击垃圾桶强制垃圾收集
制作快照 3
搜索 b2Body，您还会发现 100 个对象数

At the last step should only be 0 objects as they have been destroyed. Instead of this you'll find this: enter image description here

现在你可以看到有很多来自 b2ContactEdge 的参考。现在，如果删除代码中的 world.Step 部分，您将只会看到 2 个对正文的引用。

如果删除此行

body.CreateFixture(fixtureDef);

或者使主体静止就不再泄漏。

我的游戏循环

...gameLoop = function(o){
    // used a lot here
    var world = o.world;

    // calculate the new positions
    var worldStepSeconds = o.worldStepMs / 1000;

    // step world
    world.Step(worldStepSeconds, o.velocityIterations, o.positionIterations)

    // render debug
    if(o.renderDebug){
        world.DrawDebugData();
    }

    // always to not accumulate forces, maybe some bug occurs
    world.ClearForces();

    // tick all ticking entities
    _.each(o.getTickEntitiesFn(), function(actor){
        if(!actor) return;
        actor.tick(o.worldStepMs, o.lastFrameMs);
    })


    // update PIXI entities
    var body = world.GetBodyList();
    var worldScale = world.SCALE;
    var destroyBody = world.DestroyBody.bind(world);
    while(body){
        var actor = null;
        var visualEntity = null;
        var box2DEntity = o.getBox2DEntityByIdFn(body.GetUserData());
        if(box2DEntity){
            visualEntity = o.getVisualEntityByIdFn(box2DEntity.getVisualEntityId());
            if(box2DEntity.isDestroying()){
                // optimization
                body.__destroyed = true;
                world.DestroyBody(body);
                box2DEntity.completeDestroy();
            }
        }
        if(visualEntity){
            if(visualEntity.isDestroying()){
                visualEntity.completeDestroy();
            }else{
                var inverseY = true;
                var bodyDetails = Utils.getScreenPositionAndRotationOfBody(world, body, inverseY);
                visualEntity.updateSprite(bodyDetails.x, bodyDetails.y, bodyDetails.rotation);
            }
        }
        // this delegates out functionality for each body processed
        if(o.triggersFn.eachBody) o.triggersFn.eachBody(world, body, visualEntity);

        body = body.GetNext();
    }

    // when a joint is created is then also created it's visual counterpart and then set to userData.
    var joint = world.GetJointList();
    while(joint){
        var pixiGraphics = joint.GetUserData();
        if(pixiGraphics){
            // In order to draw a distance joint we need to know the start and end positions.
            // The joint saves the global (yes) anchor positions for each body.
            // After that we need to scale to our screen and invert y axis.
            var anchorA           = joint.GetAnchorA();
            var anchorB           = joint.GetAnchorB();
            var screenPositionA = anchorA.Copy();
            var screenPositionB = anchorB.Copy();
            // scale
            screenPositionA.Multiply(world.SCALE);
            screenPositionB.Multiply(world.SCALE);
            // invert y
            screenPositionA.y = world.CANVAS_HEIGHT - screenPositionA.y
            screenPositionB.y = world.CANVAS_HEIGHT - screenPositionB.y

            // draw a black line
            pixiGraphics.clear();
            pixiGraphics.lineStyle(1, 0x000000, 0.7);
            pixiGraphics.moveTo(screenPositionA.x, screenPositionA.y);
            pixiGraphics.lineTo(screenPositionB.x, screenPositionB.y);
        }
        joint = joint.GetNext();
    }

    // render the PIXI scene
    if(o.renderPixi){
        o.renderer.render(o.stage)
    }

    // render next frame
    requestAnimFrame(o.requestAnimFrameFn);
}

来自 Box2d 的代码：

b2ContactManager.prototype.Destroy = function (c) {
var fixtureA = c.GetFixtureA();
var fixtureB = c.GetFixtureB();
var bodyA = fixtureA.GetBody();
var bodyB = fixtureB.GetBody();
if (c.IsTouching()) {
this.m_contactListener.EndContact(c);
}
if (c.m_prev) {
c.m_prev.m_next = c.m_next;
}
if (c.m_next) {
c.m_next.m_prev = c.m_prev;
}
if (c == this.m_world.m_contactList) {
this.m_world.m_contactList = c.m_next;
}
if (c.m_nodeA.prev) {
c.m_nodeA.prev.next = c.m_nodeA.next;
}
if (c.m_nodeA.next) {
c.m_nodeA.next.prev = c.m_nodeA.prev;
}
if (c.m_nodeA == bodyA.m_contactList) {
bodyA.m_contactList = c.m_nodeA.next;
}
if (c.m_nodeB.prev) {
c.m_nodeB.prev.next = c.m_nodeB.next;
}
if (c.m_nodeB.next) {
c.m_nodeB.next.prev = c.m_nodeB.prev;
}
if (c.m_nodeB == bodyB.m_contactList) {
bodyB.m_contactList = c.m_nodeB.next;
}
this.m_contactFactory.Destroy(c);
--this.m_contactCount;
}


b2ContactFactory.prototype.Destroy = function (contact) {
    if (contact.m_manifold.m_pointCount > 0) {
        contact.m_fixtureA.m_body.SetAwake(true);
        contact.m_fixtureB.m_body.SetAwake(true);
    }
    var type1 = parseInt(contact.m_fixtureA.GetType());
    var type2 = parseInt(contact.m_fixtureB.GetType());
    var reg = this.m_registers[type1][type2];
    if (true) {
        reg.poolCount++;
        contact.m_next = reg.pool;
        reg.pool = contact;
    }
    var destroyFcn = reg.destroyFcn;
    destroyFcn(contact, this.m_allocator);
}

我也有同样的问题，但我想我知道它从哪里来。

而不是 m_* 尝试函数，例如GetFixtureA()代替m_fixtureA.

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