[Opensim-dev] Questions about Vehicle scripting calls

James Stallings II james.stallings at gmail.com
Fri Jul 6 15:53:24 UTC 2012


Greetings,

Here are some links to theory, problems, and solutions to linear
combination of vectors, which is the problem space under consideration.
Unfortunately, recognition of the problem space is about the limit of my
ability wrt the topic. That said, hopefully one of you folks can take this
research and run with it :)

Cheers!
James/Hiro

http://en.wikipedia.org/wiki/Linear_combination
http://equalrightsforall.net/classical_mechanics/Rectilinear_Motion/Kinematical_Equations/001_Vector_Combination.htm
http://www.khanacademy.org/math/algebra/algebra-matrices/v/matrices-to-solve-a-vector-combination-problem




On Thu, Jul 5, 2012 at 5:33 PM, Justin Clark-Casey <jjustincc at googlemail.com
> wrote:

> 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)
> http://justincc.org/blog
> http://twitter.com/justincc
>
>
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