Constructors.

[schteppe]

I was just wondering, is it possible to use other constructors of Bullet classes than the first?

For example, the btHingeConstraint. It's got four constructors:

new Ammo.btHingeConstraint (rbA, rbB, pivotInA, pivotInB, axisInA, axisInB, useReferenceFrameA)
new Ammo.btHingeConstraint (rbA, pivotInA, axisInA, useReferenceFrameA)
new Ammo.btHingeConstraint (rbA, rbB, rbAFrame, rbBFrame, useReferenceFrameA)
new Ammo.btHingeConstraint (rbA, rbAFrame, useReferenceFrameA)

(See http://www.bulletphysics.com/Bullet/BulletFull/classbtHingeConstraint.html for full doc.)

The first constructor seems to work (see the ragdoll demo), but nothing happens when I try any other constructor. Did I miss something obvious here?

[kripken]

It should be possible to use different overloaded constructors, assuming they are differentiated by the number of parameters.

For btHingeConstraint, looking in the generated code (bullet/build/bindings.js or builds/ammo.new.js - they only exist if you build locally though), there is

function btHingeConstraint(arg0, arg1, arg2, arg3, arg4, arg5, arg6) {
  if (arg3 === undefined)
    this.ptr = _emscripten_bind_btHingeConstraint__btHingeConstraint_p3(arg0.ptr, arg1.ptr, arg2.ptr);
  else   if (arg4 === undefined)
    this.ptr = _emscripten_bind_btHingeConstraint__btHingeConstraint_p4(arg0.ptr, arg1.ptr, arg2.ptr, arg3);
  else   if (arg6 === undefined)
    this.ptr = _emscripten_bind_btHingeConstraint__btHingeConstraint_p6(arg0.ptr, arg1.ptr, arg2.ptr, arg3.ptr, arg4.ptr, arg5.ptr);
  else 
    this.ptr = _emscripten_bind_btHingeConstraint__btHingeConstraint_p7(arg0.ptr, arg1.ptr, arg2.ptr, arg3.ptr, arg4.ptr, arg5.ptr, arg6);
  btHingeConstraint.prototype.__cache__[this.ptr] = this;
  this.__class__ = btHingeConstraint;
}

which looks like it handles the 4 cases. Or at least tries to - I haven't tested it myself ;)

Can you provide a testcase that shows the problem you are seeing?

[schteppe]

After working some more with this, I realized there is nothing wrong with the constructors. I can use the two first constructors without problem, see my double pendulum at: http://granular.cs.umu.se/ammo/Demos/PendulumDemo/

I cannot seem to be able to use the 3rd or 4th constructor though (which uses local frames). No matter how I use them, the constraint seem to be unsolveable and blow up.

I have tried to port the Ragdolldemo from the original Bullet Physics trunk and also this simple demo: http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=9&t=3191, without success.

I'm fine with using pivots and axes, but I find it annoying to not be able to use frames. I'll do some more testing and come back.

Did anyone else try to use the frame-based hinge constraints?

[RodrigoHamuy]

Hi @schteppe , did you found the issue with this? I was trying to port the FokLiftDemo from Bullet and it uses the frame-based btHingeConstraint. Whenever I apply this hinge my objects will get NaN positions.

[schteppe]

@RodrigoHamuy it was a loooong time ago... Don't really remember. If I solved it back then, you can probably find the solution here: https://github.com/schteppe/ammo.js-demos

[RodrigoHamuy]

Thanks @schteppe ! The frame based constructor is there now. The issue for me was that it didn't work if you set the hinge limit to 0,0. Instead, I use 0.0001 now and it works. Anyway, yeah, this is a super old issue, thanks for answering!

[bberak]

Hey @RodrigoHamuy can you give some more details about your fix? I've set my limits to 0.0001 but I'm still getting NaN values for my body transformations..