Re: [Flightgear-devel] Sky dive free fall

[Josef Duschl]

leee schrieb:
> On Saturday 30 May 2009, Curtis Olson wrote:
>   
>> On Sat, May 30, 2009 at 12:02 PM, Vivian Meazza  wrote:
>> 
>>>  I don’t see much of a problem with a suitable jumper. Making
>>> it a ballistic object with drag and mass would be easy. But a
>>> more realistic FDM … Hmmm
>>>   
>> An accurate FDM would be immensely complex considering all the
>> possible poses a human can achieve.  But perhaps something
>> simplistic could be worked up using the arms and legs as control
>> surfaces.  My focus right now is not so much getting accurate
>> free fall dynamics, but to get a nice jumper model and then just
>> hack up some sort of dynamics with approximately the right
>> lift/drag ratio for someone is a stable free fall pose.
>>
>> The goal would be to get approximately the right fall rates and
>> timings so that there is training value in solving problems and
>> overcoming various combinations of faults with in a realistic
>> time frame.  It's still only a very partial simulation but
>> hopefully a step better than just sitting around in a circle
>> talking through various scenarios.
>>
>> The next step would be to have a canopy that could be configured
>> to have various problems opening up and be able to draw that
>> somehow from the perspective of the sky diver, and perhaps have
>> some appropriate dyanmics for partially tangled or partially
>> inflated chutes?  Obviously there's endless variabiltiy and high
>> fidelity in all respects would be crazy to try to achieve, but it
>> would be interesting to take a few small steps forward and see
>> how far we can get.
>>
>> Best regards,
>>
>> Curt.
>> 
>
> Is lift actually much of a factor in free-fall skydiving?  I thought 
> it was mostly just varying drag, in which case the FDM might be 
> simpler than you think.  For example, the YASim FDM assigns drag to 
> extended gear elements, which are located at specific points on the 
> aircraft and so act at those points.  It might be possible then to 
> hack the YASim FDM about a bit to remove the need to solve for 
> cruise and approach conditions and just use the gear drag bits, 
> which could then be placed and animated to simulate a human body.
>
> LeeE
>   
Why not start by look for skydiving gps tracks on the net to come up 
with a model?

Cheers,

Josef

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Re: [Flightgear-devel] Elevation trouble with Scenery

[Josef Duschl]

Hi there,

did you ask on the forum about that? There's currently a good discussion 
going on about how to do it. There's also a few hints on what can go wrong.
http://www.flightgear.org/forums/viewtopic.php?f=5&t=3230
(Yes I know that this thread is about Windows but a lot of the things 
that went wrong are concerning paths. So _do_ please take a look at it.)

But from what you've written, I've got the sneaking suspicion that you 
are using a weird version of terragear. At least I don't know about a 
tool called demchop - I only know one called hgtchop.
Putting that aside, thre's more: Note that genapts also needs the 
elevation data. Also look out for any error message the tools spit out 
along the lines of "cant find file .". They should point you towards what's going wrong exactly. 
Maybe you've missed a few tiles, you need or they are in the wrong 
place. (One of the tools looks for the tiles in a set of hard-coded 
folders.)

Cheers,

Josef

cullam Bruce-Lockhart schrieb:
> I've been mucking around trying to build my own scenery for the last 
> couple weeks, with a VAST amount of help from Geoff McLane. I've got 
> it all working, and have been able to generate my own scenery.
>
> However, the elevation is coming out all messed up. Geoff has some 
> photos of how it has come out available on his site:
> http://geoffair.net/tmp/cullam-01.htm
> Almost all the land data is appearing completely flat, at -m. 
> There are a few pieces of land that appear at sea level. All airports 
> are at sea level.
>
> I'm working on the scenery for the island of Newfoundland. I'm using 
> the DEM data available from
> http://geobase.ca/geobase/en/data/cded/index.html\, which has a 
> resolution of about 30m. According to the Terragear tools, this data 
> is in the correct ASCII format, and is good to go for demchop.
>
> After running demchop on about 380 of these files, the folder 
> containing the chopped elevation data is 131.1 MB.
>
> I then run genapts on my apt.dat file which was modified to include 
> airports that aren't in the official apt.dat, and to correct their 
> layouts. Again, there don't appear to be any problems.
>
> For my shapefile, I'm simply using the standard North American vmap0. 
> This appears to have been prepared without incident.
>
> And then I run fgfs-construct. After the construction is done, my 
> total folder size for everything just generated is 7.1 MB. This has 
> GOT to be where the elevation data is disappearing, but I have no idea 
> why. Obviously, there are massive ammounts of specifics that I could 
> get into, but then this question would be huge and complex. So all I'm 
> asking here is, does anybody have any idea where I should start 
> looking to figure out where this went wrong?
>
>
> 
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