[ODE] vector has zero size

Wouter Mollemans wouter.mollemans at gmail.com
Wed Oct 18 07:12:31 MST 2006

I don't think the problem arises from performing simulations with small 
ERP or CFM values. To clarify:
after i call the nearcallback function and perfrom dCollide(), the 
position of most contact points is completely correct. Only for a few 
(most often only for one point) a NaN position value is returned. So I 
don't think that simulation goes wrong.

Best regards

Hampus Soderstrom wrote:
> Hi,
> I think the best way to get rid of this is to fine tune ERP and CFM values.
> If it is a case of exploding simulation that causes this, adding damping 
> and making sure the mass of objects isn't to small can also help.
> /Hampa
> On 18 Oct 2006, at 8:20 PM, Wouter Mollemans wrote:
>> Thx I will try to use your solution, but this is of course only a work
>> around.  Does anyone has an idea what causes these infinite values?
>> Is it the collision detection algorithm? I noticed that the collision
>> algorithm (dCollide()) frequently reports a NaN value for the position
>> value of the first contact (contact[0]).
>> Alex Green wrote:
>>> Apporx once every 12000 simulations I get the same error. The error can
>>> be detected. I run a function called 'checkPhysicsForError()' per frame.
>>> It works as follows:
>>> bool checkPhysicsForError(void){
>>> dReal *pos = (dReal*) dBodyGetPosition(bodyID of one of my boxes);
>>> if(!(pos[0]==pos[0]) || !(_finite(pos[0])))
>>> {
>>>     dWorldDestroy(world);
>>>     reset all my stuff
>>>     create everything again;
>>>     rewind one test (ie do the one that failed from the beginning);
>>>     return true;
>>> }
>>> else return false;
>>> }
>>> Notes:
>>> pos[0] == pos[0] checks for NAN (not a number);
>>> _finite() is windows, is there a cross platform check?
>>> Cheers -alex
>>> Wouter Mollemans wrote:
>>>> After some debugging, I noted that some of the collision points are
>>>> lying at infinity. This causes dNormalize4() to go nuts. Has anyone
>>>> seen this problem before and do you know what causes this effect?
>>>> Greetz
>>>> Wouter
>>>>> Hi,
>>>>> In my simulator I try to fit two rigid objects into eachother (a
>>>>> little bit like a 3D puzzle).  The rigid objects are trimeshes
>>>>> (around 4000 triangles) and all my joint are of the type contact.
>>>>> Sometimes this works nicely, but mostly I get following message: "ODE
>>>>> message 2 : vector has zero size" emmtted by dNormalize4().
>>>>> Consequently the velocity becomes Nan and my simulation is ruined.
>>>>> Is there a solution? Is there a maximum number of triangles that can
>>>>> be used or what is the source of the error?
>>>>> Thanks
>>>>> Greetz
>>>>> Wouter
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