[Opensim-dev] Questions about Vehicle scripting calls

[Bengt Falke]

I am also interested in physics for vehicles mainly for creating working yacht and for making my free moving scripted animals to work in a smooth way.
If there is a way I can contribute I will try to do so.

6 jun 2012 kl. 01:46 skrev Mike Higgins:

>     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 and 0006040 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 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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