Question

我正在玩box2djs。我试图找到一种方法来编写'onCollision（）'回调函数，但文档很稀疏，我找不到明显的方法来做到这一点。

谢谢！

Answer 1

回调box2djs实际上被称为碰撞“过滤器”。以下是如何实现它。我还会展示我正在做的事情，这可能有点慢，但由于我的另一种方法是在步骤（）之外，我可以销毁对象和东西：

// Called whenever a collision occurs in the world
//

var JellyCollisionCallback = function()
    {
    // Required function - this is the function the gets called when b2ContactManager registers a collision between two bodies
    //
    this.ShouldCollide = function( shape1, shape2 )
        {
        // These are the two bodies…
        //
        var cBody1 = shape1.m_body;
        var cBody2 = shape2.m_body;

        // I'm setting userData when I create the body object
        //
        var jellyObject1 = cBody1.GetUserData();
        var jellyObject2 = cBody2.GetUserData();


        // This is the code from the default collision filter
        //
        if (shape1.m_groupIndex == shape2.m_groupIndex && shape1.m_groupIndex != 0)
            {
            return shape1.m_groupIndex > 0;
            }

        var collide = (shape1.m_maskBits & shape2.m_categoryBits) != 0 && (shape1.m_categoryBits & shape2.m_maskBits) != 0;

        return collide;
        }

    return this;
    }


function createWorld()
    {
    var world = new b2World(worldAABB, gravity, doSleep);

    myCollisionCallback = new JellyCollisionCallback();

    world.SetFilter(myCollisionCallback );
    }

可能不如真正的回调那么好，但我最初在尝试回调工作时遇到了麻烦，因此我编写了这种方法并最终保留了它。我在调用world.step（）

的主循环中执行此操作

// Find collisions between selected objects
//
// (world is the main b2World object)
//
var aContact;
for ( aContact = world.m_contactList; aContact != null; aContact = aContact.m_next )
    {
    var cBody1 = aContact.m_shape1.m_body;
    var cBody2 = aContact.m_shape2.m_body;

    // I'm setting userData when I create the body object
    //
    var jellyObject1 = cBody1.GetUserData();
    var jellyObject2 = cBody2.GetUserData();

    // Not one of my controlled Objects
    //
    if ( typeof(jellyObject1) != "object" || jellyObject1 == null )
        continue;
    if ( typeof(jellyObject2) != "object" || jellyObject2 == null )
        continue;

    // Call my collision event for the colliding objects
    //
    jellyObject1.dink();
    jellyObject2.dink();
    }

文档几乎无法从我发现的内容中获得，但我真的很喜欢box2djs并且终于找到了完成一些简单的爱好项目所需的一切。以下是一些扩展原始box2djs demo jellyrobotics box2djs project

的示例

在box2djs中的碰撞事件处理程序

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