[ODE] Arbitrarily positioning bodies connected by joints

Deak Szabolcs ancient at ludens.elte.hu
Mon Jul 30 04:21:31 MST 2007

"The anchor is specified in world coordinates" - means that *you* specify the 
anchor in world coordinates when you set it. It is then transformed to the 
body space of the bodies connected by the joints, and it is used in the 
relative coordinate form for all internal calculations.
So both statements are true, and the relevant one in this case is that you 
*don't* have to reset anchors if you transform the connected bodies except for 
those anchors that are set to the world. In fact, resetting the anchors could 
induce/enhance joint drift since joints are usually not *perfectly* satisfied 
during any timestep..

Beau Albiston wrote:
>  From the ODE manual: "the anchor is specified in world coordinates."  
> If your body frame and world frame are aligned, then your statement is true.
> -Beau
> dan miller wrote:
>> I do this all the time, without resetting anchors.  Why would that be
>> necessary?  It's relative to the bodies, not global coords (unless you're
>> anchored to the world)

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