Re: [Pyode-user] PyODE joint properties accessible as parameters

[<al...@ci...>]

Since the patch file is too large, I have compressed it in order to reach the
mailing list.

> Hello,
>
> Here is the patch for accessing joint parameters as properties.
>
> Examples:
>
> j = ode.HingeJoint(world)
> j.param.lo_stop = 0
> j.param.cfm = 1e-5
> j.param.vel = 0.1
>
> For complex joints:
> joint.param[1].fmax = 1
> joint.param[2].fmax = 2
> joint.param[3].fmax = 3
>
> And for Plane2D:
> joint.paramX.cfm = 1e-5
> joint.paramY.cfm = 1e-10
> joint.paramAngle.cfm = 1e-10
>
> Or:
> joint.param['X'].cfm = 1e-5
> joint.param['Y'].cfm = 1e-10
> joint.param['Angle'].cfm = 1e-5
>
>
> The patch also contains PUJoint, PRJoint, PistonJoint and Joint.enable/disable,
> so it can be applied
> against latest git revision.
>
>
> I have tried to use 'Strip trailing spaces' in the editor, but now I have
> another problem.
> There are a lot of lines in the patch which do not change anything.
> e.g. (instead of dots, there are spaces):
> -....
> -      BallJoint(world, jointgroup=None)....
> +
> +      BallJoint(world, jointgroup=None)
>
> How should I get rid of these? Manually editing the patch? Git Gui does not help
> me
> (i.e. 'Stage/Unstage hunk from commit' does not work properly, and messes the
> entire patch)
>
> Alex
>
>> al...@ci... wrote:
>>> In ode.pyx there is a comment:
>>>
>>> ## This causes some kind of weird bug! Need to fix this.
>>>
>>> import weakref
>>>
>>> _geom_c2py_lut = weakref.WeakValueDictionary()
>>>
>>> In my programs, sometimes the lut is not able to find the geom ID,
>>> and Space.collide_callback() fails with a KeyError. When this happens,
>>> some boxes pass through the floor and fall down to -infinity.
>>> Using a normal dictionary seems to solve the problem.
>>>
>>> Is this the weird bug?
>>
>> It sounds related but this isn't exactly the bug I was confused about
>> when I wrote that comment. The bug is that if you create Geoms but don't
>> save references to them, (like the "geoms" list in tutorial 3) then the
>> geoms get garbage collected and they therefore don't have any collisions.
>>
>> Your bug sounds related, because it seems like geoms are getting garbage
>> collected, but if that's true, then they should be getting destroyed
>> with dGeomDestroy() and so not causing collisions.
>>
>>> Therefore, we have two possibilities to solve the conflict:
>>>
>>> A) Overriding __setattr__:
>>>
>>>    Pros: - compatible with existing code
>>>
>>>    Cons: - may be slow (overriding __getattr__ and __setattr__ slows down the
>>> access to class items)
>>>          - you are not warned at all if you misspell the name of a property
>>>           (e.g. you use body.pos = (1,2,3) but the correct name is
>>> 'body.position'; however, python will not complain at all)
>>>
>>> B) Custom data field:
>>>    Pros: - more lightweight
>>>          - works fine, with no conflicts
>>>          - if you misspell the name of a property, you will receive an error
>>>
>>>    Cons: - breaks existing code which uses custom data
>>
>> I like B better. It would be really great if we could offer a setting
>> that would enable backwards-compatible behavior, though :)
>>
>>> Which one should we choose? I prefer B) since it already works on my
>>> computer.
>>>
>>> I have also implemented a mechanism for accessing joint parameters as
>>> properties.
>>> It works like this:
>>>
>>> j = ode.HingeJoint(world)
>>> j.param.lo_stop = 0
>>> j.param.cfm = 1e-5
>>> j.param.vel = 0.1
>>>
>>> For complex joints:
>>> joint.param[1].fmax = 1
>>> joint.param[2].fmax = 2
>>> joint.param[3].fmax = 3
>>>
>>> And for Plane2D:
>>> joint.paramX.cfm = 1e-5
>>> joint.paramY.cfm = 1e-10
>>> joint.paramAngle.cfm = 1e-10
>>>
>>> Or:
>>> joint.param['X'].cfm = 1e-5
>>> joint.param['Y'].cfm = 1e-10
>>> joint.param['Angle'].cfm = 1e-5
>>>
>>> And of course, the joint parameters are visible at TAB completion.
>>
>> Sounds like a good idea to me.
>>
>> Ethan
>>
>