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Thanks for sharing, this sounds exciting!
The NNCG method uses the projected conjugate gradient, I couldn't find it in
your patch. Did you implement PCG?
When you apply your patch to a fresh Bullet revision 2613 checkout (no other
changes) it seems that there is no friction for contacts anymore (check out the
BasicDemo). Is that a known issue?
Original comment by erwin.coumans
on 4 Sep 2013 at 5:00
Gabor admitted that though he didn't check the full proof and understood the
Math only in a level to be able to implement it; it seemed to him that the
solution in the cited documentation based on the simple Projected Gauss Seidel.
So he used the one already implemented in the Bullet.
You are right the friction didn't work. It was unfortunately a bug. The reason
why we didn't find it was that the friction in our primary tests are not too
determinative. For our defense: this happened, because the solverconstraints of
the frictions weren't initialized to zero similary to the solverconstraints of
the user joints. :-(
We have fixed it now.
Also we added a little test to the fixed patch to be able to check the benefit
more easily.
Please check the RagdollDemo. Lift the snake with the mouse and shake it a
little. By default the NNCG+SPGS are on. You can turn those off with 'e'.
The iterationcount is quite high so Release version is recommended.
Please note that: at one end a cube is loose. This behavior is not lost with
NNCG+SPGS.
The benefit of SPGS is not that clear here. In our more complex test cases
without this the system would blow off.
Original comment by nsark...@gmail.com
on 5 Sep 2013 at 12:05
Attachments:
Thanks for sharing, I'll check it out. The patch has some conflicts with latest
trunk, need to look into that.
Original comment by erwin.coumans
on 8 Sep 2013 at 5:02
The btNNCGConstraintSolver is in latest trunk and in the github repo.
If certain things are missing, please report at
https://github.com/bulletphysics/bullet3
Original comment by erwin.coumans
on 30 Mar 2014 at 5:52
Original issue reported on code.google.com by
nsark...@gmail.com
on 4 Sep 2013 at 10:40Attachments: