I was talking to Justin Clark-Casey at the OpenSim developers meeting
this morning, and he suggested that the mailing lists would be the
easiest way to have a conversation about vehicle physics on OpenSim.
Justin you there? Is this where you meant? Anyone else want to talk
about vehicle scripting in OpenSim?
I am in the process of testing the OpenSim vehicle scripting calls
and
trying to find out what works and what can be worked around. I am
submitting mantis reports when I think I see a true bug, issue
numbers
0006039 <http://opensimulator.org/mantis/view.php?id=6039> and
0006040
<http://opensimulator.org/mantis/view.php?id=6040> for starters.
Instead
of submitting 1000 line vehicle scripts that do not work, I am
writing
small 10-line scripts that demonstrate a particular problem.
Issue 0006040 <http://opensimulator.org/mantis/view.php?id=6040> is
particularly interesting because if my hypothesis is correct, the
linear
motor direction is being actively projected onto the global XY
plane. I
cannot get an airplane to glide up, or a balloon to rise using the
linear motor. (Hover height works with balloons, but not the linear
motor even with hover height disabled). The interesting thing
about this
is that my hypothesis suggests that there is extra code doing this
projection onto the XY plane. I checked the vehicle flags and there
isn't one that should force this extra projection into the
calculations.
Vehicle type balloon is supposed to have all the flags removed,
but just
to be sure I used the remove call to clear them all. The linear motor
still cannot go up. Can someone familiar with the code look at the
linear motor and tell me why this is happening and if there is a
way to
disable it? (I tried turning flags like
VEHICLE_FLAG_NO_DEFLECTION_UP on
to see if this flag was inverted, and if it applied to the motor
instead
of deflection, but no luck).
The fun thing is that I can write one kind of vehicle that works
well --
assuming this bug is there. I built a vehicle that has the linear
motor
set to <0,0,20>, pointing straight up. When the vehicle is perfectly
horizontal, the projection of this motor onto XY is <0,0,0> and the
vehicle does nothing. But then when you tilt the vehicle in any
direction, the projection of the linear motor on XY becomes
non-zero and
causes it to start moving in the direction of tilt. This feels a lot
like an RL helicopter, so I used the control keys to pitch down/up to
move forward/backwards, added yaw left and right, and used
page-up/down
to increase/decrease the hover height. I put it in a hacked together
helicopter build and it is a lot of fun!
I'm looking for work-arounds for the current vehicle routine
behaviors.
One work-around for an airplane is to turn on hover height, check the
airplane speed and pitch once a second in timer(), calculate what
altitude the plane should get to in the next second, and set hover
height to that altitude. The things we do to get stuff working!
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