Topic: Bug Report: 0.3.3 build 696. Flying Gerber is sticky and loses momentum

[Rosencrantz]

Version: 0.3.3 build 696
Reproducability: Always.

Abstract: Collision causes gerber and ship to stick, afterwards hitting brings up the Cel window.


Description:
A collision between your ship and the gerber is a quasi inelastic collision. In addition to this after removing your ship from the flying gerber it continues to rotate. Eventually it stops rotating suddenly. At this point if your ship touches the gerber then you encounter the CEL error window mentioned in bug #82.

System:
Windows 98 SE
Athlon XP 2200+
512 MB Ram.
Geforce 4 MX440

--Rosencrantz

[Morgul]

This is a nasty bug in ODE. Rotating bodies are unstable, and increase rotational speed, until the rotational matrix overflows, and ODE think it has infinitite rotational velocity, which it can't handle, so it stops rotating it at all. (This is from personal experimentation.)

I was going to say that we might need to find a new physics engine, or do several hack-ish fixes, however I found this: http://sourceforge.net/tracker/index.php?func=detail&aid=1335194&group_id=24884&atid=382801

It is a patch that only conserves angular velocity, not angular momentum. Some realism is lost: asymmetric bodies will rotate symetrically. however, we can make this appear to happen on our own, by putting the center of gravity not in the center of the mesh.

The sticky part I think is simply our elasticity settings. I think we make things too soft.

Also, this was listed as 'mesh to mesh collision fix' which might help us out. Unfortunately, SourceForge went down for maintenece right before I clicked on it, so I'm only putting it here so I don't have to go finding it again.

http://sourceforge.net/tracker/index.php?func=detail&aid=1335183&group_id=24884&atid=382801

We will test these patches out, and possibly they will make it into the next release.

[Neo]

Rosencrantz: Good format on the bug report. I aprove.

~Reynard