Away3D Forum Physics piston type movement?

Alex Bogartz, Sr. Member
Posted: 17 September 2011 12:51 AM Total Posts: 216

Is it possible to make a rigid body (or something similar) move like a piston along a given axis? I’m trying to make a ledge move back and forth along the x-axis. The ledge has a mass of zero so it doesn’t fall and is supposed to be “floating”. Any ideas?

Alex Bogartz, Sr. Member
Posted: 17 September 2011 03:09 PM Total Posts: 216 [ # 1 ]

The answer lies somewhere in here, perhaps? I haven’t had enough time to play with it.

https://github.com/away3d/awayphysics-examples-fp11/blob/e7cd5ba317ec0cc4d390ee1c45572b5ddd1c4166/src/ConstraintTest.as

If anyone has a quick explanation I’d be very grateful.

John Brookes, Moderator
Posted: 17 September 2011 04:19 PM Total Posts: 732 [ # 2 ]

In that example theres one called slider. It uses AWPGeneric6DofConstraint
Instead of passing two meshes, just pass one.
It should then be a constraint between the ledge and the world.

ps there is a physics section on the forum :p

Alex Bogartz, Sr. Member
Posted: 17 September 2011 10:32 PM Total Posts: 216 [ # 3 ]

New physics forum? YES!

Thanks, I’ll take a look!

Alex Bogartz, Sr. Member
Posted: 19 September 2011 07:28 PM Total Posts: 216 [ # 4 ]

Hi, so there’s one thing about those physics examples that doesn’t seem ideal, and that is that you’re using a timer to decide when to change directions. Part of the problem is that there’s no event fired when a constraint object reaches it’s end point, is there? So I made a new function in AWPGeneric6DofConstraint. It uses AS3 Signals (I know you guys are using that but maybe this idea would be helpful using Events?):

public function testForLimit():void
  {
   if (getTranslationalLimitMotor().targetVelocity.x > 0)
   {
    if (getTranslationalLimitMotor().lowerLimit.x - getTranslationalLimitMotor().currentLinearDiff.x * 100 > -1)
    {
     xLimitReached.dispatch(this);
    }
   } else
   {
    if (getTranslationalLimitMotor().upperLimit.x - (getTranslationalLimitMotor().currentLinearDiff.x * 100) < 1)
    {
     xLimitReached.dispatch(this);
    }
   }
   if (getTranslationalLimitMotor().targetVelocity.y > 0)
   {
    if (getTranslationalLimitMotor().lowerLimit.y - getTranslationalLimitMotor().currentLinearDiff.y * 100 > -1)
    {
     yLimitReached.dispatch(this);
    }
   } else
   {
    if (getTranslationalLimitMotor().upperLimit.y - (getTranslationalLimitMotor().currentLinearDiff.y * 100) < 1)
    {
     yLimitReached.dispatch(this);
    }
   }
   if (getTranslationalLimitMotor().targetVelocity.z > 0)
   {
    if (getTranslationalLimitMotor().lowerLimit.z - getTranslationalLimitMotor().currentLinearDiff.z * 100 > -1)
    {
     zLimitReached.dispatch(this);
    }
   } else
   {
    if (getTranslationalLimitMotor().upperLimit.z - (getTranslationalLimitMotor().currentLinearDiff.z * 100) < 1)
    {
     zLimitReached.dispatch(this);
    }
   } 

So in my game loop, I do something like this:

if (generic6Dof)
    {
     generic6Dof.testForLimit();     
    } 

When I create the constraint, I add this:


generic6Dof.xLimitReached.add(reverseLedge)

Which simply triggers this:

private function reverseLedge(constraint:AWPGeneric6DofConstraint):void
  {
   constraint.getTranslationalLimitMotor().targetVelocity = new Vector3D(-constraint.getTranslationalLimitMotor().targetVelocity.x, 0, 0);
  } 

Any thoughts on this approach? Am I missing something built in?

Thanks!

Yang Li, Administrator
Posted: 20 September 2011 03:34 AM Total Posts: 80 [ # 5 ]

looks good, will test. any idea about angular motor?

Alex Bogartz, Sr. Member
Posted: 20 September 2011 03:04 PM Total Posts: 216 [ # 6 ]

Yang Li - 20 September 2011 03:34 AM
looks good, will test. any idea about angular motor?

You mean triggering an event when the target rotation is met? I’m not sure yet. I was just approaching this like you might in a tweening engine where you can set an onComplete function to fire. I think that would be a really useful addition to the constraints.

John Brookes, Moderator
Posted: 20 September 2011 04:58 PM Total Posts: 732 [ # 7 ]

Maybe just check the linear/angular velocity

Alex Bogartz, Sr. Member
Posted: 20 September 2011 05:02 PM Total Posts: 216 [ # 8 ]

I just personally prefer the event or signal driven method. Rather than have a list of items to test for, I’d like to just add a listener and wait for each event to trigger.

Physics piston type movement? Software: Away3D 4.x

Alex Bogartz, Sr. Member Posted: 17 September 2011 12:51 AM Total Posts: 216 Is it possible to make a rigid body (or something similar) move like a piston along a given axis? I’m trying to make a ledge move back and forth along the x-axis. The ledge has a mass of zero so it doesn’t fall and is supposed to be “floating”. Any ideas?
Alex Bogartz, Sr. Member Posted: 17 September 2011 03:09 PM Total Posts: 216 [ # 1 ] The answer lies somewhere in here, perhaps? I haven’t had enough time to play with it. https://github.com/away3d/awayphysics-examples-fp11/blob/e7cd5ba317ec0cc4d390ee1c45572b5ddd1c4166/src/ConstraintTest.as If anyone has a quick explanation I’d be very grateful.
John Brookes, Moderator Posted: 17 September 2011 04:19 PM Total Posts: 732 [ # 2 ] In that example theres one called slider. It uses AWPGeneric6DofConstraint Instead of passing two meshes, just pass one. It should then be a constraint between the ledge and the world. ps there is a physics section on the forum :p
Alex Bogartz, Sr. Member Posted: 17 September 2011 10:32 PM Total Posts: 216 [ # 3 ] New physics forum? YES! Thanks, I’ll take a look!
Alex Bogartz, Sr. Member Posted: 19 September 2011 07:28 PM Total Posts: 216 [ # 4 ] Hi, so there’s one thing about those physics examples that doesn’t seem ideal, and that is that you’re using a timer to decide when to change directions. Part of the problem is that there’s no event fired when a constraint object reaches it’s end point, is there? So I made a new function in AWPGeneric6DofConstraint. It uses AS3 Signals (I know you guys are using that but maybe this idea would be helpful using Events?): public function testForLimit():void { if (getTranslationalLimitMotor().targetVelocity.x > 0) { if (getTranslationalLimitMotor().lowerLimit.x - getTranslationalLimitMotor().currentLinearDiff.x * 100 > -1) { xLimitReached.dispatch(this); } } else { if (getTranslationalLimitMotor().upperLimit.x - (getTranslationalLimitMotor().currentLinearDiff.x * 100) < 1) { xLimitReached.dispatch(this); } } if (getTranslationalLimitMotor().targetVelocity.y > 0) { if (getTranslationalLimitMotor().lowerLimit.y - getTranslationalLimitMotor().currentLinearDiff.y * 100 > -1) { yLimitReached.dispatch(this); } } else { if (getTranslationalLimitMotor().upperLimit.y - (getTranslationalLimitMotor().currentLinearDiff.y * 100) < 1) { yLimitReached.dispatch(this); } } if (getTranslationalLimitMotor().targetVelocity.z > 0) { if (getTranslationalLimitMotor().lowerLimit.z - getTranslationalLimitMotor().currentLinearDiff.z * 100 > -1) { zLimitReached.dispatch(this); } } else { if (getTranslationalLimitMotor().upperLimit.z - (getTranslationalLimitMotor().currentLinearDiff.z * 100) < 1) { zLimitReached.dispatch(this); } } So in my game loop, I do something like this: `if (generic6Dof) { generic6Dof.testForLimit(); }` When I create the constraint, I add this: `generic6Dof.xLimitReached.add(reverseLedge)` Which simply triggers this: `private function reverseLedge(constraint:AWPGeneric6DofConstraint):void { constraint.getTranslationalLimitMotor().targetVelocity = new Vector3D(-constraint.getTranslationalLimitMotor().targetVelocity.x, 0, 0); }` Any thoughts on this approach? Am I missing something built in? Thanks!
Yang Li, Administrator Posted: 20 September 2011 03:34 AM Total Posts: 80 [ # 5 ] looks good, will test. any idea about angular motor?
Alex Bogartz, Sr. Member Posted: 20 September 2011 03:04 PM Total Posts: 216 [ # 6 ] Yang Li - 20 September 2011 03:34 AM looks good, will test. any idea about angular motor? You mean triggering an event when the target rotation is met? I’m not sure yet. I was just approaching this like you might in a tweening engine where you can set an onComplete function to fire. I think that would be a really useful addition to the constraints.
John Brookes, Moderator Posted: 20 September 2011 04:58 PM Total Posts: 732 [ # 7 ] Maybe just check the linear/angular velocity
Alex Bogartz, Sr. Member Posted: 20 September 2011 05:02 PM Total Posts: 216 [ # 8 ] I just personally prefer the event or signal driven method. Rather than have a list of items to test for, I’d like to just add a listener and wait for each event to trigger.

Physics piston type movement?

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