[ODE] Fixing bodies to static environment

["Francisco J. Parreño Fernández"]

Hi again!

Thanks for this fast answer.  I've fixed my problem and now, I 
understand what means "static environment". Thank you very much.

My problem was that when I fixed a body to the ground, my robot (a 
snake) jumps without control. I thought that the problem was the way of 
defining the link between a segment and the ground but it wasn't. 
Really, the problem was that I didn't define the slider's axis :-( and 
this made that the segment jumped to the coords (0, 0, 0).

For fixing a segment to the ground I decided to use a slider and set its 
"dParamLoStop" and "dParamHiSlop" to zero for avoiding movements (it 
seems that it works...). By this way, the slider works as an axis of 
fixed length.

Thanks again. See you!

Remi wrote:
> Hi,
>
>>
>> I'm developing a robot simulator using ODE as dynamic engine and I 
>> need to fix a piece of my robot to the ground. The manual says /"To 
>> attach this joint to only one body, set body1or body2 to zero - a 
>> zero body refers to the static environment"/ and I don't exactly 
>> understand what means /"static environment"/.
>
> I hope I will be able to better explain the concept.
>
> It will be attached to your global frame or world frame or universe 
> frame.
> This is the frame that never move in ODE.
>
> When you attache a joint with one of the body set to NULL you attache 
> the joint to the global frame.
>
>>
>> Furthermore, I've thought on using a slider and a hinge joint to fix 
>> a body to the ground, what do you think about this? 
>
> Depending on how you set your axis and force and limits it could 
> possibly move.
>
>> Is there any better idea? 
>
> If you have the base of your robot that doesn't not move you can have 
> a geometry only there if you need collision. The first joint with 
> motion will be attached to NULL and first_body_to_move_rotate
>
>
>> What about to use a fix joint?
> I'm using it for development but they said to not use it in production.
>
>>
>> Thank you very much. Grettings!
>>
>> P.D.: My apologies for my poor english, I'm Spanish and I don't speak 
>> English very well. If somebody doesn't understand something and he or 
>> she speaks Spanish, I write the same message but in my dear sweet 
>> language :P
>
> Me it is French !!!
>>
>>     Hola!
>
> Salut !!
>>
>>     Estoy desarrollando un simulador de robots usando ODE como motor
>>     dinámico y necesito fijar una parte de my robot al suelo. El manual
>>     dice que "...." y no entiendo exactamente qué significa "entorno
>>     estático".
>>
>>     Además, he pensado en usar un slider y un visagra para fijar el
>>     cuerpo al suelo, ¿qué pensáis de esto? ¿Hay alguna idea mejor? ¿Qué
>>     os parece usar un "fix joint"?
>>
>>     Muchas gracias. ¡Saludos!
>>
>
>
> Remi
>