[ODE] Fw: Universal Spring

[Jon Watte (ODE)]

How much gap is there between the boxes? If the boxes are super tight, 
they will keep intersecting, and force will be created by pushing the 
blocks out of each other. Try adding 5% margin between the blocks and 
see if it's any better.

Also, there will always be some stretch. You have to experiment with 
CFM, ERP, step size and body damping, as well as float vs double 
precision, to see if you can find a compromise that works for you.

Cheers,

          / h+


Edgar wrote:
> Hi,
>
> Since I see you are applying patches.
>
> I have made a simple sample application, of 3 heavy blocks connected by universal hinges.
> The first block is connected to the world.
> When I initialise all block in a horizontal plane, the blocks start falling, and swinging.
> Like 3 pendulums connected to eachother.
> Since my object are 20.000 kg, a lot for force is put on the hinges.
> And the hinges start to get stretched.
>
> This never gets solved again.
> I tried smaller timesteps, but the problem remains.
> Modifying CFM and ERP doesn help..
>
> I found in the mailing list a suggestion with a fix:
>   
>>>> http://ode.org/pipermail/ode/2002-August/005725.html
>>>> Universal Spring: like universal joint, expanded with a linear spring that
>>>> keeps the bodies together and an angular spring that keeps the bodies
>>>> aligned.
>>>>         
>
>
> But it didnt had any follow up.
>
> Is anybody noticeing the same problems ?
> This is a very simple demo, so in larger project you would have even more problem I think..
>
>
>
> Regards,
> Edgar
>
>
> PS:
> I dont know if I posted this multiple times, since it seems my messages didn't get to the list
>
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