Box2d冲突beginContant不止一次发生

Question

基于box2d文档和在Internet中找到的教程(这里最好的一个是http://www.iforce2d.net/b2dtut/collision-anatomy)，我假设碰撞事件处理程序beginContact每次碰撞只发生一次。

但我的经验是，在某些情况下(到目前为止，我无法将其缩小到特定的范围)，beginContact被多次调用。

具体例子：

1st fixture is a box, belongs to static body and is a sensor

2nd fixture (which is also player body in 2d game I'm building) 
is a polygon, belongs to dynamic body and is not a sensor.

Both are large enough so in debug mode it is absolutely clear 
when these fixtures start to overlap and when they part. 

Result is - while player body fixture passes through static sensor, 
beginContact is called 3-4 times or more while fixtures keep oveplapping. 
Velocity is moderate (fixtures keep overlapping for a whole second and more).

我是不是错过了文档里的东西？有办法绕过这件事吗？

Answer 1

好吧，我想我找到了答案，或者至少找到了解决办法。也许它会对某人有帮助。

问题中的多边形夹具实际上是一个ChainShape。在这种情况下，这条链的每一个环节似乎都开始了联系。切换到常规PolygonShape解决了这个问题。

我认为这是手册中描述这种情况的部分：

Contacts are objects created by Box2D to manage collision between two fixtures. If the fixture has children, such as a chain shape, then a contact exists for each relevant child. 

Answer 2

除了这两种外，世界上还有别的固定装置吗？您是否正在检查以确保BeginContact事件确实适用于这两个装置？这种"3-4次“行为是否会让您怀疑BeginContact可能用于其他固定装置，而不是静态传感器？

我的猜测是，你的玩家正在移动一个由多个固定装置组成的地面，你看到的是播放器和地面装置之间的BeginContact事件。