[quake3-bugzilla] [Bug 4329] New: Very fast func_train mover has ugly side effects

[bugzilla-daemon at icculus.org]

http://bugzilla.icculus.org/show_bug.cgi?id=4329

           Summary: Very fast func_train mover has ugly side effects
           Product: ioquake3
           Version: SVN HEAD
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: Misc
        AssignedTo: zakk at icculus.org
        ReportedBy: bougard.g at gmail.com
         QAContact: quake3-bugzilla at icculus.org


Created an attachment (id=2193)
 --> (http://bugzilla.icculus.org/attachment.cgi?id=2193)
Patch backported from Smokin'Guns fix to ioQuake3 rev1729

Mappers may use func_train movers with a very high value to have them move
instantaneously. In Smokin'Guns engine we discovered very ugly side effects...
To try it out, you can install Smokin'Guns 1.0 and load the Santa Fe Express
map. This map is heavily using func_train movers.

I found that when the func_train speed is too high, the duration of the travel
can be nullified. But the problem is that duration is used later to calculate
the box of the move to detect any collision. With nullified duration, the move
box becomes infinite, so every entities in the map collide with the move. The
result in our Sante Fe Express map is at each time a mover trigger the case,
the ground entity set for each entity changes to that mover for just one frame.
The side effect is to have the feeling of a freezing as we are forced to move
in a way we didn't expect.

The attached patch fixes our Santa Fe Express case. The patch first forces the
move duration to be at least equal to 1. Secondly, in some case, the fast move
can be seen by clients (didn't find really why, maybe prediction problem) so we
just remove the mover from the frames sent to clients as this mostly what
clients expect: the mover is teleported.

This seems to be completly a game problem and I think it concern any mod, not
only our game. Btw I don't think many map use func_train movers with very high
speed...

Tequila
Smokin'Guns team.

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