[ODE] XML and ODE

[William Denniss]

John,


On 04/08/2005, at 3:05 AM, John Donovan wrote:

>
> 7) Should there be scope for handling spaces defined in different  
> files?
> So you can have a car.xode and place that in a world with another car
> from the same file.
>

This is an implementation issue, and is handled by the reference  
implementation.  Basically what I did is allow the end-developer to  
give a prefix which is added to all names.  Thus, you can have "car1- 
frontwheel", "car2-frontwheel" etc.


> 8) There is no "absolute" attribute for joint anchor elements.
>

This could be a bug, or it could be unsupported.  Are you referring  
to the reference implementation?



> 9) Why doesn't the world element have any of the ODE world settings,
> like gravity?
>

An omission in the spec.  Since you are thinking of this, can you  
please list for me all the attributes you think it should have?

Remembering this statement:
"  It is OPTIONAL that parsers actually create seperate World instances
    in ODE for each <world> they encounter."

On 04/08/2005, at 11:36 PM, John Donovan wrote:

>
> 10) It doesn't say in the spec whether triangle indices should be
> 0-based or 1-based.
>

Like ODE itself, it is 0-based.


> 11) This is a more general ODE question, the docs imply that the  
> Vel and
> FMax axis parameters are only for amotor joints. Is this the case?
> Because the XODE truck example sets these parameters for the  
> wheels, and
> odd behaviour happens (the wheels barely turn, and the front of the
> chassis sinks lower and lower until it collides with the ground). If I
> disable these parameters, then the truck freewheels nicely down the
> slope.
>

I believe you can set Vel and FMax values can be set for many joints.

See: http://ode.org/ode-latest-userguide.html#sec_7_5_1

The docs just say "If a particular parameter is not implemented by a  
given joint, setting it will have no effect.".  They don't actually  
specify for which joints this applies.  I know it works for Hinge2,  
because I use it.

The behaviour you see is odd because I haven't really spent a lot of  
time getting that example looking good.

Cheers,

Will.