Hi ,
Vivian Meazza schrieb am 21.12.2007 00:11:
> I wrote:
>
>   
>> Sent: 19 December 2007 09:17
>> To: 'FlightGear developers discussions'
>> Subject: RE: [Flightgear-devel] External Cargo, was: Re: 
>> screenshots (and "snapshots")
>>
>>
>>
>>
>>     
>>> -----Original Message-----
>>> From: [EMAIL PROTECTED]
>>> [mailto:[EMAIL PROTECTED] On 
>>> Behalf Of Maik Justus
>>> Sent: 18 December 2007 23:12
>>> To: FlightGear developers discussions
>>> Subject: Re: [Flightgear-devel] External Cargo, was: Re: 
>>> screenshots (and "snapshots")
>>>
>>>
>>> Hi Viviam,
>>> Vivian Meazza schrieb am 18.12.2007 23:41:
>>>       
>>>> I've just a few moments ago added a few lines of code to
>>>>         
>>> AIBallistic
>>>       
>>>> which apply an external force (using the same math as
>>>>         
>>> above). The rest
>>>       
>>>> works as before. I just need few properties to set the
>>>>         
>>> magnitude and
>>>       
>>>> vector of the external force and it will be done, at least for
>>>> testing.
>>>>         
>>> Thank you, very good. Is it possible to pass the forces in the earth
>>> fixed coordinates axes base? (in Newton or pof)?
>>>       
>> I'm planning, and have tested the passing of the force in 
>> terms of magnitude (pound force), azimuth (degrees, north = 
>> 0) and elevation (degrees, horizontal = 0, up = 90). I hope 
>> this is what you need, and can work with.
>>
>>     
>>>> It's trivial
>>>> really, but I'm assuming that the external force applies no
>>>>         
>>> rotational
>>>       
>>>> force to the object.
>>>>         
>>> I think this could be easily faked. e.g. new_roll = old_roll +
>>> cos(old_roll) * force_in_y_direction * a_magic_constant * dt 
>>> but i f I read the code correctly, yaw and hdg are pointing 
>>> at the speed 
>>> direction (slightly filtered)? Therefore we need something 
>>> like _elevation = atan2(force_in_z_direction,force_in_x_direction)
>>> and then your filter to add some inertia?
>>>       
>> Right now there are 2 options - 1, the ballistic object 
>> aligns with the velocity vector (damped), or 2, it remains 
>> static. These options both work with the new code. I think 
>> option 1 will do for an under slung load?
>>  
>>     
>>>> I haven't a great deal of time available in the run up to
>>>>         
>>> Christmas so
>>>       
>>>> no promises on completion.
>>>>   
>>>>         
>>> Same here. I will have very limited access to my computer (family
>>> visiting tour). Fortunately my computer is a notebook, but I 
>>> am not sure 
>>> if there is any space in the car for my joystick.
>>>       
>> We have a horde of family visitors over the coming days - all 
>> competing for my time and the computer. We'll see how much 
>> can be done (not a lot I expect).
>>
>>     
Similar here (but with the difference, that we are part of the horde of 
family visitors ;-)  )

>
> Christmas has arrived slightly early! I've got something which:
>
> A. runs
>
> B. looks OK with limited testing
>
> The ballistic object aligns with the direction of flight in pitch and
> heading with an external force applied. It would be possible to align it
> with the direction of the external force, but I think that would need roll
> as well. I'm not sure which one would look best.
>
> The external force is defined in terms of:
>
> Magnitude (lbf)
> Azimuth (deg, North = O)
> Elevation (deg, up = 90)
>
> In a user-defined property. Of course, some external program needs to set
> the external force data.
>
> This all now needs testing in a more realistic environment. I'm not totally
> convinced that the ballistic object won't disappear into space/to the centre
> of the earth, or oscillate like a deranged spring.
>
> Vivian
>
>   
I will try to combine this with YASims winch feature (but I think I will 
not find time earlier than end of the month).

Maik


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