[ODE] Joint instability with small bodys

[Darabos Dániel]

You might try the experiment without fixed joints, they do not work
very well for me (they keep wiggling with QuickStep). For creating a
fixed body use the method described in the FAQ.
I don't know however how the problem could be related to the size of
the objects.

BTW I might have a related problem. I changed the units in the
boxstack demo to have 9.81 as the gravity and ever since the boxes
fall into the ground as if they were falling into a swamp. I was
completely unable to figure it out. I changed around the CFM and ERP
parameters and now its tolerable, but still worse than in the original
demo.
Also increasing the number of iterations helped, but that's pricy.
There might be a dark secret lurking however...

Daniel

On 6/7/05, Patrick McColgan <patrick at torcinteractive.com> wrote:
> Hello, I'm having difficulties with using the standard ODE joints with
> 'small' objects.
> 
> Whilst bodies with dimensions around and below 0.2 are fine colliding as
> rigid bodies, creating constraints between them produces constant
> instability.  My basic test has been to have a static body floating in
> midair (using a fixed joint) and then attach another body to it using a
> ball or hinge, the joined bodies do not collide with each other and are
> not close enough to collide with anything else.
> 
> Has this come up before?  I searched the archives but found nothing I
> felt was relevant, I know it has been said here before that measures
> should be kept around 1.0, certainly constraints prove to be fine with
> higher values but has anyone come across this before and maybe found
> ways to deal with it?
> 
> I'mn using double precision but is this likely to be a numerical
> inaccuracy problem?
> 
> 
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