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Saab 37 Viggen

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Re: Saab 37 Viggen Development

Postby Johan G » Fri Nov 25, 2016 8:59 pm

I looked at some YouTube videos today and found among other these three.

One thing I noted was that contrary to most other aircraft there is little or no vortexes forming on the main wings wingtips. Instead they mainly form at the tips of the canard wings.
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Re: Saab 37 Viggen Development

Postby Necolatis » Sat Nov 26, 2016 9:09 am

Ah yes, I will change it to do that, thanks. :)
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Re: Saab 37 Viggen Development

Postby Necolatis » Mon Dec 26, 2016 8:49 pm

The Viggens 2016 X-Mas update 4.011:

Overview since 4.008
=======
Wingtip vapour is now canardtip vapour
M71 now has CCIP
New HUDs by Pinto
2 new liveries by Spectre
Weapons flying and radar logic now consumes less framerates.
Throttle control has changed, the afterburner will now start at much lesser throttle setting.

Full changelog here: https://raw.githubusercontent.com/NikolaiVChr/flightgear-saab-ja-37-viggen/master/Aircraft/JA37/changelog.txt
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Re: Saab 37 Viggen Development

Postby abassign » Mon Jan 02, 2017 11:44 pm

Image

The aircraft has been reviewed on FGFS Italy on Facebook ( https://www.facebook.com/flightgearitalia/ ), is really nice and I hope that other fans can try it. In the review I have included some negative comments on exterior and interior lights (it would be better to do a simlar solution as done for F20). However the aircraft really spectacular!
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Re: Saab 37 Viggen Development

Postby Necolatis » Tue Jan 03, 2017 12:27 am

Thank you, nice review. I tried auto translating the review, but did not understand the part about lights.
I have been wanting to use Thorstens ALS exterior lights, but haven't gotten around to it yet. :)
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Re: Saab 37 Viggen Development

Postby abassign » Tue Jan 03, 2017 9:02 am

Necolatis wrote in Tue Jan 03, 2017 12:27 am:Thank you, nice review. I tried auto translating the review, but did not understand the part about lights.
I have been wanting to use Thorstens ALS exterior lights, but haven't gotten around to it yet. :)



I insert two examples:

Your work:

Image

and the F20 example:

Image

They both used the ALS method (I've also used it recently), is a great method because it allows the modulation of light as a function of ambient light. The problem is the choice of texture. In reality the lights using the planes have not much glare, the lights should not be too intense, the F20 uses the much more "transparent" texture and then the result is a better match to reality.
Have you never seen a plane with so bright lights? I do not, especially for a fighter. There are formation lights, which are luminescent strips. Then the tail flashing white light does not fill the image, it is normally perceived by the eye, visible only as a white dot at a distance, but nothing more. You do not trust the pictures, often nocturnal ones are on display with shutter speeds rather long, which tend, for the camera, to form patches of color. In reality, the eye is very adaptive and tends to avoid turning a bright spot in a large patch of color.

Rear color for F20:

Image

Look this example:

Image

Time ago I had discussions with the pilots to know the output color of the exhaust gases at normal operating conditions. Honestly many have told me that they did not know which color had, since no jet aircraft flying behind another as the air would be low in oxygen and therefore run the risk one shutdowns of the reactor. He studied it on a physical level, and then two things I noticed:
First: the combustion of a modern turbo-reactor is complete, and then the flame in the combustion chamber is blue.
Second: In the 50-60 years engines, the output of gas was very hot so the duct of the gas turned red (not much for the truth, at 700-800 ° C we see a very faint red at night). In bypass engines definitely the conduit of the gas is cold (less than 600 ° C) and then our eye sees nothing. Then, of course, if you activate the afterburner, the music changes!

A note for the color of the combustion chamber at night, look at the work done sull'F20, I would say it is closer to reality. I think you can use the same technique dell'F20 (which I also used it previously). Just make luminescent (on blue) the last blading of the output stage and make it rotate, by a good effect, must be very small because the room temperature is high and the flame emits a near color to blue. Edit the luminescence as a function of engine speed. Remember that during the day the luminescence is not seen. However if you follow what has been done nell'F20 on lights and on combustion, in my opinion, your plane gets really ok :)
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Re: Saab 37 Viggen Development

Postby J Maverick 16 » Tue Jan 03, 2017 2:44 pm

Necolatis wrote in Mon Dec 26, 2016 8:49 pm:Throttle control has changed, the afterburner will now start at much lesser throttle setting.

That's why I consume such a lot of fuel recently... ;)
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Re: Saab 37 Viggen Development

Postby Thorsten » Tue Jan 03, 2017 2:44 pm

They both used the ALS method (I've also used it recently), is a great method because it allows the modulation of light as a function of ambient light.


My two cents on that one:

The light intensity (aka color value) actually should not be changed. The 'halo' around the lights however is a real optical phenomenon (the Airy disc) but not in itself a glowing object - it arises from the imperfection of any optical system (and in reality it disappears with the central light source, though we don't model that).

Whether you can see the Airy disc (which has rapidly fading intensity at the edges) or not depends on the contrast of the central light with the surrounding surfaces, i.e. you see it much better in low light. Now, because our computer screen is 2 dim and doesn't produce the real 3d emitting characteristics of a light, the focusing problem of the eye when looking at a real or rendered light is different, and so is the intensity range the screen can display - so we don't get proper Airy discs by just rendering the central light, we have to put it in by hand - and so we also have to put its fading with ambient light in by hand.

Having said that, I stand by my earlier statement that for real emitting sources (such as a flame) the contrast with the surrounding scene automatically controls how bright it is perceived, and that emissive values of secondary light sources should never depend on daytime if their intensity is chosen properly. Just in this case the Airy disc not being a real object makes it a different problem.
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Re: Saab 37 Viggen Development

Postby Mada00 » Tue Jan 03, 2017 8:35 pm

Hello, your plane is magnificent. I saw that the back-landing gear- does not have a suitable space, in fact invades the fuselage. I think is a real shame for the beautiful work you did.
in any case, congratulations!

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Re: Saab 37 Viggen Development

Postby Necolatis » Tue Jan 03, 2017 9:21 pm

I agree its a shame. Will probably be fixed at some point.
Last edited by Necolatis on Sun Jan 15, 2017 10:28 pm, edited 1 time in total.
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Re: Saab 37 Viggen Development

Postby Necolatis » Sun Jan 15, 2017 10:26 pm

The Viggen is now at version 4.015

Overview of changes since 4.011
==========================
Spectre added 2 liveries.
Nasal garbage collection optimizations in HUD
Thrust reverser now depends on some relays for gear compressions, as per electrical diagram in manual.
Speedbrakes added, only deploy beneath mach 0.92. (no external animation though)
Inverted flight will now make oil pressure drop. Too much, and engine will start to cut out.
Various controls added to cockpit mainly thanks to Pinto, about half of those is functional.

Full changelog here: https://raw.githubusercontent.com/Nikol ... ngelog.txt


Made 2 tutorials on youtube. Sorry if they are a bit amateurish.

The first gives an overview of the plane for newcomers to it:

The second goes into more details of startup, taxi and takeoff:


Around 5 more is planned.
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Re: Saab 37 Viggen Development

Postby Thorsten » Mon Jan 16, 2017 3:45 pm

This is excellent work! I've just spent a very pleasant hour goofing around in Corsica.

Just one stupid question - the help says that I should land with ~220 km/h - yet when I do, I always get to hear a 'Low speed!' warning, right until I'm very close to the ground. It sort of works anyway, but I get the feeling I'm still not doing everything right. What am I missing?

Edit: Some more comments

* the FDM feels great, with all the right details in the right places

* the sounds are also very impressive with a lot of attention to detail

* I didn't really make too much progress on what the different HUD modes are supposed to do or when they switch - is this documented somewhere?

* maybe I've been landing too many Shuttles (which is most emphatically *not* STOL), but the wheel brakes seem awfully efficient to me - is this real?

* the vapour trails are the usual standard implementation - which unfortunately is blinding white at night. I can show you how to properly color all particle systems with the ambient light if you're interested - it's not particularly involved. Though personally I prefer Erik's idea of using the thruster flame to model them

* is the touchdown vspeed/acceleration checked for gear damage, or did I finally learn to land aircraft in one piece :mrgreen: ?
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Re: Saab 37 Viggen Development

Postby Necolatis » Mon Jan 16, 2017 6:45 pm

The throttle must have been very low, just give a little more throttle and the warning should not come. The low speed warning comes below 1200 m alt and with landing gear out; above 30 agl meters, but only when throttle is put very low and speeds below 375 Km/h.

The landing instructions in the help needs an update btw. I will do that when I get to tutorial #4 about landing as there will be some changes before, related to how the HUD helps with landing.
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Re: Saab 37 Viggen Development

Postby Thorsten » Wed Jan 18, 2017 5:43 pm

The throttle must have been very low, just give a little more throttle and the warning should not come


Full idle I remember. The warning is a bit counter intuitive (I may be criticizing Saab here) - because with throttle just a bit higher, I was able to go much lower in speed without triggering the warning. But okay, I managed to fly a few approaches without triggering it now.

What I didn't manage is to de-frost the canopy. I switched aircon to warm and dialed the temperature all the way up, but at high altitude it wouldn't thaw (okay, I've been at 15 km). Only by going low again I got rid of the ice, triggering a warning that I'm sweating next. Really good job with the air condition simulation!

I also managed to stall it (at least the audio said so), but I didn't go into a spin, the behavior was in general very mild.

So - where are the Swedish audio files :mrgreen: ? (Not that I am a qualified Swedish speaker, but living in officially bi-lingual Finland for ten years, I can usually read it quite well and understand some of it - in fact, before becoming a good Finnish speaker, I would usually try to read the Swedish instructions on anything because it's closer to German).

***

The following is my personal preference: I'd really like to see a pdf-manual of the plane. With so many details, it'd be worth it.

I suppose many will like your video tutorials, and I'm sure it's lots of work - but for me the information density is just too low. The two tutorials you have posted last 30+ minutes - in that time I can read 50 pages of technical documentation and get tons of details. And I can easily read back on what's important now and skim what's not.

Also, going through the preflight and startup checklists is nice - but it misses out one important element - the why. Why am I pressing this and that button now? What would happen if I would not? what would happen if I changed the sequence?

It's the reason why I have intentionally not structured the Shuttle checklists to allow auto-completion of checklist items - because you don't learn what you're doing from that. Whereas if you read the manual, you see the diagram which button you press in sequence alongside the text which tells you why you do it.

Real joy and appreciation of a plane only comes from understanding the how and why in my opinion.
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Re: Saab 37 Viggen Development

Postby Necolatis » Wed Jan 18, 2017 6:22 pm

You are right, I should make a manual, thanks for the idea. :)

I will look into the air-conditioning, maybe something has been broken along the way, haven't intentionally touched the code for a year or so I think. Except for putting up those warnings about sweating and such.

Well, as for audio sounds, I must admit I have been cheating a bit. The real Viggen has different beeps and such for warnings. I just thought the average FG user would not want to study 10+ sound warning freq. in detail to be able to fly the plane, (I might be wrong), so I made them spoken out.

As for the pre-flight checklist most can be used in another order, just don't let the battery on for too long, without charging it (by either generator, ram air turbine or ext. power). The engine start checklists should be followed more strict. Btw. with ram air turbine on, notice it wont charge the battery if gears is down.
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