Re: Reducing airports polygon count

Curtis L. Olson wrote:

> Dale E. Edmons wrote:
>
>> I don't consider it insane at all, more like terribly inconvienent 
>> due to the horrible things I'm trying to make it do--display approx 
>> 200 polygons per display per frame!  I've actually found a way to 
>> exceed that limit for the general terrain.  I'll be better able to 
>> judge once I get my Terragear version debugged.  I'm judging based on 
>> FGSD output right now.  Though very similar, they aren't exactly the 
>> same.
>
>
>
> Do you have any screen shots of the sort of output quality/complexity 
> that your system can currently achieve with it's original databases?  
> ... general terrain ... on approach to a runway/airport, etc.?
>
We've moved our modeling system to an X11 based on, but the modeling 
software still uses the old library.  I'm hoping X11 will still do a 
screen grab.  I'll give it a try and see what happens.  (Steve Baker 
originally worked on the system.  I can blame him if it don't work.  ;)  )

>> Two would be nearly equivalent to  modeling the  runway flat.  I'm 
>> just trying to avoid what we'll actually end up doing.  Use the 
>> TerraGear version as a rough-in and re-model each airport by hand.   
>> The RAS system coming up is going to tax us and the equipment to the 
>> very limit (hopefully not beyong) of what is required in terms of 
>> accurately modeled airports.  RAS, as I understand it, is to be tied 
>> into the EGPWS.  The  EGPWS gives terrain elevation map on the radar 
>> display.  The RAS will be kind of like one of the city street maps 
>> tied to a GPS in a car.  RAS will be for airports and taxiways.
>
>
>
> Remind me what RAS and EGPWS stand for?
>
EGPWS = Enhanced Ground Proximity Warning System.  The "enhanced" part 
is a terrain height database that gets displayed on the weather radar 
display head on older cockpits.  It's a little bit like a moving map 
display.  The terrain color changes from black to green to yellow to red 
as the aircraft approaches terrain at the altitude of the aircraft.  RAS 
is a new system coming out that ties into EGPWS and GPS but is said to 
give callouts of taxiways, lengths, crossings etc....  I haven't seen 
one yet but our aircraft are to be equipped with them soon and training 
will be improved if the callouts and the visual scene actually match.  
So, I'm hoping we can gear up to provide effective training, but I need 
more info.

>
>> That's why I'm using FlightGear.  Quality is the important part!  
>> Once I understand the code better and finish debugging my current 
>> stuff, I'll take a serious look at this.  Especially if a user 
>> selectable parameter could be added to affect the desired end count 
>> similar to what can be done for the terrain, that would be a very 
>> good solution.
>>
>> 1) Certification.  I believe that FGFS as been through certification 
>> on "Training Equipment" or maybe even for FTD's, but I don't think 
>> its been certified for a Level C/D Full Flight simulator--even a 
>> grandfathered one.  On my system at home I notice that FGFS display 
>> will stop at certain intervals and continue on.  Granted its only 
>> momentary (maybe 1/4 sec or less) but noticable.  When we put an 
>> O-scope on the signal and do the step response tests as required by 
>> the FAA, I reasonably expect FGFS would fail--if only intermittantly.
>
>
> What frame rate do you need to sustain?  You can throttle FG back to 
> 30hz or 20hz with a command line option ... it's possible to have 
> hardware that is a bit iffy for sustaining 60hz, but will solidly hold 
> 30hz.

I can't remember if its 60 Hz or a little less.  I can get it if you 
need it.  It should be on the FAA website.

> Also, you can throw additional hardware at the system.  A scsi disk 
> subsystem will improve load performance over ide because scsi does 
> direct dma transfers to memory, where ide reads need to involve the 
> cpu rather heavily.  There's no difference when you load your MS word 
> document, but there can be a big difference if you are trying to load 
> scenery in a threaded scenery loader and render the display at the 
> same time.
>
I removed my scsi because of  the noise.  Maybe I'll put it back in for 
a test it with only scenery on it.

> For Level3 FTD they don't take a close look at the display rate so we 
> got off pretty easily there ourselves.
>
Our FTD's don't even have displays!  (e.g. framerate=0)  :)  What I'm 
very interested in doing, if the instructors think it would be 
beneficial, is to use FGFS on them.  It'd be low cost and fairly easy to 
do from the sound of it.  However, they often want the students to not 
fly by visual cues and they may object even though one could turn them 
off rather easily.  Money will be a factor too.  My idea is to use 
projector's as displays.   Anyway...

>> 2) Hooking a PC to a caligraphic projector is non-trivial.  
>> Converting the projection system to a raster only display is 
>> non-trivial.  There are some vendors doing exactly that and we're 
>> looking into equivalent FAA certified systems, but that brings up 
>> item 3).
>
>
>
> Hey, that's an area I don't know too much about.  If you figure 
> something out or can explain the issues I'd love to hear about it.
>
>> 3) Cost.  If we can purchase an equivalent system with new IG then 
>> I'll still be doing the same thing except that polygon count will no 
>> longer be a major problem.  But, cost-cutting has become an absolute 
>> imparative in the Airline industry in its current form.  Even then 
>> we're only looking at replacing one of the two systems--unless things 
>> change.  If management gives us the funds I'll be very happy indeed.
>
>
>
> Yah, these high end display systems are not cheap ... especially when 
> you get into systems that can warp themselves to project on a dome, 
> and systems that do edge blending and such.  Well good luck with all 
> that!  You are definitely operating on a slightly higher plane.  I'd 
> love to get there someday, and am happy to benefit from your 
> experience. :-)

We have the "Wide" type visual systems on all but one of our full flight 
sims.  120deg continuous display that is about 2m tall.  Three edge 
matched RGB projectors make it look like one continuous screen.  I 
couldn't afford one.

If you ever take a trip to Seattle let me know in advance and I'll give 
you a full tour.  It'll likely be at midnight if the sims are all scheduled.

Keep up the good work!


Dale

>
> Regards,
>
> Curt.
>


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