[Opensim-dev] Questions about Vehicle scripting calls

[Justin Clark-Casey]

On 05/07/12 16:19, Mike Higgins wrote:
>      No time! No time!
>      But I have thought about it a little. It seems to me that the problem is that gravity and buoyancy are probably
> done from accelerations, while the linear motor is a magic device that specifies a target velocity. Ideally you could
> calculate the force of gravity, the counteracting force of buoyancy, and calculate a force that would result in the
> linear velocity. Sum all the forces into one and apply them to the object. But I don't think the physics is done in a
> manner that "realistic".
>      What is SUPPOSED to happen when gravity and the linear motor are combined? Seeing as the linear motor specifies the
> end velocity, it should overpower (ignore) gravity. What happens in SL when you turn on the linear motor on a falling
> object? I suspect that it simply turns in the linear motor direction. Hopefully making a smooth turn in the decay time.
> I'll have to go do physics experiments in SL to figure out what they implimented.
>      Then I don't know enough about the Open Simulator code to know how to implement whatever is necessary. Given enough
> time (see my first comment above) I could get more involved with that..

That would be very welcome.  As always, time is the constraint for many of us as well, as are the many other bugs and 
issues that OpenSimulator has :)

>
> On 7/4/12 2:53 PM, Kevin Cozens wrote:
>> On 12-06-08 06:15 PM, Mike Higgins wrote:
>>> Then I looked in the ODEDynamics.cs code where, starting at line 663, the
>>> comments from KF say "So far I have found no good method to combine a
>>> script-requested .Z velocity and gravity". Then he proceeds to replace the
>>> requested linear motor Z value with the current Z velocity of the body.
>>> Since a balloon is buoyant, the Z of the current velocity is always 0 and
>>> this looks like it is probably the problem. It always resets the linear
>>> motor Z value to 0 here. I'll have to think about what should be done here...
>>
>> Nice catch, Mike. Have you had time to investigate this any further?
>>
>
>
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Justin Clark-Casey (justincc)
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