Hello!
Sorry for not coming to you sooner, things were happening rather turbulently lately.
So looking into this particular case under a magnifying lens, it turns out that in the PhysX 4.1.2 they improved the TGS solver so that it doesn’t loose that much energy as it used before. For that, it appears to be a change, but it’s not a breakage, it’s an improvement actually. It only seems to affect the TGS solver mode. Let me illustrate.
Consider a cube on a spring joint like this one:
Assume there is no damping:
It appears that with the PGS solver, in both of the PhysX versions the cube’s trajectory decays even without any damping at all (damping inherent to the solver’s projections). Here is the first 10 seconds of the capture:
However, with TGS there is some difference, as in the new PhysX 4.1.2 version TGS no longer decays that fast at all (the joint might appear weaker due to that?).
If we were to repeat the same experiment with a spring joint that has some damping, here are the graphs we’d get.
Again, in PhysX 4.1.1 there is no difference between PGS and TGS – they both get the same trajectory:
In addition to that, PGS results in the same trajectories comparing 4.1.1 and 4.1.2. However, in 4.1.2 there is a difference between PGS and TGS.
Hope that makes some sense now.
Anthony