[Opensim-dev] Questions about Vehicle scripting calls

[James Hughes]

I have been experimenting with trains in SL and would like to make a 
physical one that works in OpenSim. Hopefully these cases aren't some 
limitation of the physics engines and can have a proper fix.

-BlueWall

On 06/05/2012 07:46 PM, Mike Higgins wrote:
> 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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