Away3D Forum Collision event doesn’t work every time when the collision occurs

programmist, Newbie
Posted: 06 August 2012 11:49 AM Total Posts: 13

I added event listener to detect when my balls collide. But this event doesn’t work properly. Why?

ballBodies[0].addEventListener(AWPEvent.COLLISION_ADDED, onCueCollided);

private function onCueCollided(event:AWPEvent):void
  {
   var b:BilliardBall = (event.collisionObject as AWPRigidBody).m_userData as BilliardBall;
   
   if (b)
   {
    if (b.getRigidBody().mass > 0.0)
    {
     if (firstContact == null)
      firstContact = b;
     
     
    }
    
    
   }
   
   
   
  } 

programmist, Newbie
Posted: 06 August 2012 11:51 AM Total Posts: 13 [ # 1 ]

I need to know with what the cue ball collided firstly but it works every two times or even rarely

John Brookes, Moderator
Posted: 06 August 2012 10:20 PM Total Posts: 732 [ # 2 ]

Have you enabled
physics.collisionCallbackOn = true;

what happens if you just trace out

event.collisionObject.skin.name

assuming its skinned and named.

programmist, Newbie
Posted: 08 August 2012 11:06 AM Total Posts: 13 [ # 3 ]

Yes, of course I’ve enabled this option.
unfortunately I don’t use skinning

John Brookes, Moderator
Posted: 08 August 2012 02:16 PM Total Posts: 732 [ # 4 ]

Point being, you need to find out what is happening inside the cuecollided.
What the collsionObjects are. Are you sure it can only be billardBall?

I seem to have lost my copy of billiard ball and thers not much to go on apart from no worky

programmist, Newbie
Posted: 09 August 2012 07:06 AM Total Posts: 13 [ # 5 ]

No, it can’t only be a billiardBall because the cueBall is rolling on the table. If event occurs with the table then variable b will be null and nothing happens.
I removed the table and gravity, so the cueBall can only collide with billiardBalls, the problem is the same(

dtramer2, Newbie
Posted: 28 July 2013 04:10 AM Total Posts: 16 [ # 6 ]

I’m suspecting this is a bug in awayphysics. I think I know what the problem is here. The same thing is happening for me.

It happens much more if you use a much higher step frequency (meaning the 3rd parameter to the away physics world step function is lower).

Some background:

The awayphysics collision callbacks are called from the awayphysics step function.

As suggested here: http://www.bulletphysics.org/mediawiki-1.5.8/index.php/Collision_Callbacks_and_Triggers
the awayphysics step function iterates over all of the contact manifolds.

The problem is that awayphysics doesn’t follow this additional advice from that link:

“This should be done during a simulation tick (substep) callback, because contacts might be added and removed during several substeps of a single stepSimulation call.”

So, what is happening is that if the collision occurs during one of those in between sub-steps, the collision callback won’t be called.

dtramer2, Newbie
Posted: 28 July 2013 05:40 AM Total Posts: 16 [ # 7 ]

Just to be clear (regarding my post above):

If you don’t pass in a sufficiently low 3rd parameter (or if you don’t pass any 3rd parameter) to the step function, then you may never (or very infrequently) encounter this bug.

John Brookes, Moderator
Posted: 28 July 2013 01:01 PM Total Posts: 732 [ # 8 ]

Just tried a basic drop ball test and yeah can confirm is an issue.
Post bug on Git

Yang Li, Administrator
Posted: 29 July 2013 02:08 AM Total Posts: 80 [ # 9 ]

can you send your test code, I’m always not reproduce this bug.

dtramer2, Newbie
Posted: 29 July 2013 12:39 PM Total Posts: 16 [ # 10 ]

Here is my call to step.

private var lastTime:int
  private function onEnterFrame(event:Event):void
  {
   var newTime:int = getTimer()
   if (lastTime)
   {
    _world.step((newTime - lastTime) / 1000.0, 15, 1 / 500);
   }
   lastTime = newTime 

Yang Li, Administrator
Posted: 29 July 2013 01:27 PM Total Posts: 80 [ # 11 ]

hi, I use this step parameter still not reproduce the bug, but I have changed collision detecting in the tick callback. you can update the latest swc.

John Brookes, Moderator
Posted: 29 July 2013 01:57 PM Total Posts: 732 [ # 12 ]

That fixes it for me.

was using this to test.
https://gist.github.com/JohnBrookes/f12de24f2e6d907fe436

dtramer2, Newbie
Posted: 29 July 2013 10:41 PM Total Posts: 16 [ # 13 ]

Fixed it for me as well. Thanks.

Collision event doesn’t work every time when the collision occurs Software: Away3D 4.x

programmist, Newbie Posted: 06 August 2012 11:49 AM Total Posts: 13 I added event listener to detect when my balls collide. But this event doesn’t work properly. Why? `ballBodies[0].addEventListener(AWPEvent.COLLISION_ADDED, onCueCollided); private function onCueCollided(event:AWPEvent):void { var b:BilliardBall = (event.collisionObject as AWPRigidBody).m_userData as BilliardBall; if (b) { if (b.getRigidBody().mass > 0.0) { if (firstContact == null) firstContact = b; } } }`
programmist, Newbie Posted: 06 August 2012 11:51 AM Total Posts: 13 [ # 1 ] I need to know with what the cue ball collided firstly but it works every two times or even rarely
John Brookes, Moderator Posted: 06 August 2012 10:20 PM Total Posts: 732 [ # 2 ] Have you enabled physics.collisionCallbackOn = true; what happens if you just trace out event.collisionObject.skin.name assuming its skinned and named.
programmist, Newbie Posted: 08 August 2012 11:06 AM Total Posts: 13 [ # 3 ] Yes, of course I’ve enabled this option. unfortunately I don’t use skinning
John Brookes, Moderator Posted: 08 August 2012 02:16 PM Total Posts: 732 [ # 4 ] Point being, you need to find out what is happening inside the cuecollided. What the collsionObjects are. Are you sure it can only be billardBall? I seem to have lost my copy of billiard ball and thers not much to go on apart from no worky
programmist, Newbie Posted: 09 August 2012 07:06 AM Total Posts: 13 [ # 5 ] No, it can’t only be a billiardBall because the cueBall is rolling on the table. If event occurs with the table then variable b will be null and nothing happens. I removed the table and gravity, so the cueBall can only collide with billiardBalls, the problem is the same(
dtramer2, Newbie Posted: 28 July 2013 04:10 AM Total Posts: 16 [ # 6 ] I’m suspecting this is a bug in awayphysics. I think I know what the problem is here. The same thing is happening for me. It happens much more if you use a much higher step frequency (meaning the 3rd parameter to the away physics world step function is lower). Some background: The awayphysics collision callbacks are called from the awayphysics step function. As suggested here: http://www.bulletphysics.org/mediawiki-1.5.8/index.php/Collision_Callbacks_and_Triggers the awayphysics step function iterates over all of the contact manifolds. The problem is that awayphysics doesn’t follow this additional advice from that link: “This should be done during a simulation tick (substep) callback, because contacts might be added and removed during several substeps of a single stepSimulation call.” So, what is happening is that if the collision occurs during one of those in between sub-steps, the collision callback won’t be called.
dtramer2, Newbie Posted: 28 July 2013 05:40 AM Total Posts: 16 [ # 7 ] Just to be clear (regarding my post above): If you don’t pass in a sufficiently low 3rd parameter (or if you don’t pass any 3rd parameter) to the step function, then you may never (or very infrequently) encounter this bug.
John Brookes, Moderator Posted: 28 July 2013 01:01 PM Total Posts: 732 [ # 8 ] Just tried a basic drop ball test and yeah can confirm is an issue. Post bug on Git
Yang Li, Administrator Posted: 29 July 2013 02:08 AM Total Posts: 80 [ # 9 ] can you send your test code, I’m always not reproduce this bug.
dtramer2, Newbie Posted: 29 July 2013 12:39 PM Total Posts: 16 [ # 10 ] Here is my call to step. `private var lastTime:int private function onEnterFrame(event:Event):void { var newTime:int = getTimer() if (lastTime) { _world.step((newTime - lastTime) / 1000.0, 15, 1 / 500); } lastTime = newTime`
Yang Li, Administrator Posted: 29 July 2013 01:27 PM Total Posts: 80 [ # 11 ] hi, I use this step parameter still not reproduce the bug, but I have changed collision detecting in the tick callback. you can update the latest swc.
John Brookes, Moderator Posted: 29 July 2013 01:57 PM Total Posts: 732 [ # 12 ] That fixes it for me. was using this to test. https://gist.github.com/JohnBrookes/f12de24f2e6d907fe436
dtramer2, Newbie Posted: 29 July 2013 10:41 PM Total Posts: 16 [ # 13 ] Fixed it for me as well. Thanks.

Collision event doesn’t work every time when the collision occurs

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