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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?<br>
<br>
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
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<span class="small"><a
href="http://opensimulator.org/mantis/view.php?id=6039"
title="[new] VEHICLE_ANGULAR_MOTOR_DIRECTION does not rotate
around the vehicle local axes">0006039</a> and </span>
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<span class="small"><a
href="http://opensimulator.org/mantis/view.php?id=6040"
title="[new] Vehicle linear motor is projected onto the region
global XY plane">0006040</a> 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. <br>
<br>
Issue </span>
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<span class="small"><a
href="http://opensimulator.org/mantis/view.php?id=6040"
title="[new] Vehicle linear motor is projected onto the region
global XY plane">0006040</a> 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).<br>
<br>
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!<br>
<br>
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!<br>
<br>
<br>
<br>
</span>
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