[Sugar-devel] Physics activity (Was: Release v3 tonight?)

[Gary C Martin]

On 13 Jul 2009, at 05:46, Asaf Paris Mandoki wrote:

> On 13 Jul 2009, at 03:11, Gary C Martin wrote:
>
>> Think we need to make a call on the stability of the new Physics  
>> Journal state format first, or at least make sure everyone knows  
>> the storage format may (or may not) be stable long term (hate to  
>> see a bunch of folks generating/posting examples for lesson plans  
>> only to have them all fail to resume in a few versions from now).
>
> Are we talking about doing something like this?
>
> http://wiki.laptop.org/go/Physics_File_Format
> (See also the discussion)
>
> I think the format described there is much too elaborate for our  
> needs although the right thing to do is implement it at the elements  
> level and that may require to do more than what we really need for  
> this activity.
>
>  JSON sounds like a good option for the format. I'll look into the  
> api we have available.

Cool, the simpler the better, my main concern would be that we should  
at least have control over the stored format should upstream change  
(unless upstream are willing to offer some guarantee of backwards  
compatibility in box2d if things do need to change).

> I also suggest scheduling an IRC meeting to discuss some "long" term  
> plans about what we're going to do and how we're going to do it.
>
>> Yes, an IRC meeting sounds like a good idea. I'm usually only on  
>> IRC for specific meetings so we'd need to pick a time. Perhaps we  
>> could make it a Physics specific ActivityTeam meeting on Friday,  
>> some other interested parties may join the discussions?
>
> Friday is only good for me if we do it around 3pm GMT.

Brian: is 3pm GMT good for you? #sugar-meeting is free by my  
calculations UK==16:00, US/Eastern==11:00.

>  I'm thinking about adding some sort of goals and objectives but I'm  
> not sure if there is where we want to go.
>
>> Well need to chat :-) but the X2o Activity seems like the place for  
>> driving "goals and objectives". I see Physics as more the open  
>> ended sand box for experiments, like a simple Paint tool for  
>> physics simulations.
>
> That sounds good to me. I'm thinking about how to include some  
> curriculum content into the activity and we could do this by  
> distributing prefabricated contraptions that demonstrate some  
> specific physical concepts or machines.

An Examples tab, with perhaps ~10 good examples of what Physics can  
do? Need to get longer term state version compatibility clarified  
first (it's working great BTW! So nice to resume and get your  
contraption back).

> We should also start considering adding some sort of Save/Load state  
> so it's easier to test tweaks to a contraption.

You mean undo/redo? Save/Load is not a Sugar thing. Hmmm. Undo/redo  
would need to snap shot the state of the entire simulation on every  
user change... Could be a tough one. Of course with Journal state  
working, the Keep button is all about keeping a version of the current  
state (allowing you to 'stop' and resume an earlier 'version') :-)

>> We need to keep an eye on the usability for younger kids, the  
>> number of tools is probably about right, but I have been looking at  
>> the idea of adding more options as secondary palettes, i.e. you  
>> hover over the circle tool and the palette includes extra options  
>> for "helium balloon", "rubber ball", "wooden ball", "stone ball"   
>> for some pre-set material types, this would vary depending on the  
>> tool, so the motor could perhaps have clockwise and anti-clockwise  
>> as well as some torque settings (strong, medium, weak).
>
>
> I was thinking on adding a toolbar at the bottom to modify the  
> properties of a selected object. This could also alter the  
> properties of newly created objects. And if the background is  
> selected you can modify the world properties. The problem with this  
> is that we need a select tool but we could integrate it with the  
> move tool.  I'll try to give this some tought before Friday.
>
>> If you can get some more friends to add translations that would be  
>> great :-)
>
> I got them to add German and French but I still need to review the  
> French because he posted them as suggestions.
>
> I think that the translator comments need to be more descriptive.

Agreed, I was a little slack in providing any when I generated  
the .pot file. Should improve if we have a new wave of feature strings.

Regards,
--Gary

> On 12 Jul 2009, at 22:39, Gary C Martin wrote:
>> How stable do you think the save format is? Using pickling might  
>> leave us at the mercy of changes in the box2d object structure.  
>> Once we release Physics-3 we'll want to be reasonably comfortable  
>> that the Journal entries it creates will continue to resume with  
>> future Physics releases.
>
> I didn't think about portability between box2d versions. I guess the  
> only way to ensure this is to manually generate a JSON structure of  
> the world and then save it. Maybe it's worth doing.
>
>> I don't know enough about the box2d pickling solution, did you see  
>> any mention of it when you were researching?
>>
> I didn't see anything that guarantees the compatibility with future  
> versions.
>
> Greetings,
> Asaf