Unusual "jitter" while hit

[AxeD]

Hi,
i have found that issue. It is not a angular velocity. It looks like getRotation().getX(), getRotation().getY(), getRotation().getZ() returns wrong sign sometimes. I don't know how to fix it.

EDIT:

I think i've got it.
Original code

Code: Select all

btScalar trace = m_el[0].x() + m_el[1].y() + m_el[2].z();
       btScalar temp[4];
         
       if (trace > btScalar(0.0)) 
       {
                    btScalar s = btSqrt(trace + btScalar(1.0));

As far as i know acoording to a theory it should be:

Code: Select all

btScalar trace = m_el[0].x() + m_el[1].y() + m_el[2].z();
       btScalar temp[4];  
       btScalar s = btSqrt(trace + btScalar(1.0));

       if (s > btScalar(0.0)) 
       {
        

Am I right?

[AxeD]

And.... jitter is back. I'm using glmatrix directly and jitter still exists. It seems to be something wrong with rotation. When i used a cylinder instead of pin shape, jitter was even higher. So I still need some help :/

[Erwin Coumans]

Most likely the jitter is because your objects are too small, Bullet currently has limitations on the sizes.

Assuming units in meters and seconds, bowling pins are just too small. There have been some games shipped, using Bullet, but this required some additional tweaking to make it stable. We can't help users with this tweaking, so it is currently unsupported. You could try to upscale collision shapes, and work around this issue.

This known issue is reported here: http://code.google.com/p/bullet/issues/detail?id=45
Thanks,
Erwin

[AxeD]

Hi Erwin,
thank You for a hint. All my objects are in CM not in meters In Meters i have just this same behaviour and i have to add that on PC all is OK Maybe there is some platform dependent calculation ?

[AxeD]

I have found solution/reason of that issue and :
1. Avoid multiple rotation conversions, in both ways (matrix <-> quaternion) - lost of precission.
2. Do not operate on pointers not taken from phx world.