[ODE] dBodyGetForce returns zero force

[Jon Watte (ODE)]

If you go this route, beware that, because of the way the integrator 
works, certain joints may be very jittery from frame to frame, but be OK 
in the averaged case. I would recommend returning a force value averaged 
over at least the last four frames to get a de-jittered value. Also, a 
leaky integrator only has 6 dB/oct rejection for jitter, so it may be 
better to integrate some known number of steps each time, rather than 
trying to keep a running average. (Illustration of the bad, 6dB/oct, 
running average method:  blah = oldBlah * (1-lambda) + newBlah * lambda)

Cheers,

          / h+


Gazi Alankus wrote:
> I think that only returns the forces that you applied to the body. I
> had to modify my ODE source and add a dBodyGetPrevForce() to get the
> force that was used in the last iteration.
>
> -Gazi
>
> On 28/06/07, PKS123 <prashant.coder at gmail.com> wrote:
>   
>> Hi
>>
>> I am using the dBodyGetForce() function to find out the force on a body
>> which is in free fall.
>> The function is returning a zero vector.
>> I noticed from the ODE Documentation that the force accumulators are set to
>> zero after each time step. So, I put the function both before and after the
>> dWorldQuickStep() function but the value was zero in both cases.
>>
>> The Body has a mass of 100, and so the minimum force that I should be
>> getting is m*g ie. 100*9.8
>> But I get a zero force. Could anyone suggest what might be wrong.
>>
>> Thanks and Regards
>> PKS123
>> --
>> View this message in context: http://www.nabble.com/dBodyGetForce-returns-zero-force-tf3993241.html#a11339547
>> Sent from the ODE mailing list archive at Nabble.com.
>>
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