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Flightgear impressions


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Hi everyone!


My name is Thorsten Renk, and perhaps not surprisingly in this forum, I have a passion for flight simulation. However, probably more for developing a flightsim than for actually using it. I'm one of the people who contribute to Flightgear, and I'd like to show some of the things we do here.


Inside the FG development team, I do quite a bunch of different things - I maintain one of the weather engines, the Atmospheric Light Scattering renderer, I tinker with terrain texturing schemes and I do many things spaceflight-related.


Why do I spend hundreds of hours coding without any pay? Because it allows me to get from the simulation exactly what I want out of it. For instance, I'm fascinated by sunsets and northern lights, so I put them into the atmosphere in great detail. I once saw a thunderstorm front at night from an airliner and was hooked, so I didn't rest till the simulation had it as well. I've always wanted to know how to operate a real spacecraft, so I started the effort to create a highly detailed sim of the Space Shuttle.


(I try to have an interesting life, so also do a couple of other things such as producing a Fantasy movie or linguistics of invented languages - feel free to visit my site if you're curious.


So let's start with some impressions of my current favourite ride - the Space Shuttle.


Here's an evening launch, first stage ascent with the SRBs still attached.




The workplace in orbit - after some three years of hard work, the avionics is now near feature-complete - my test pilot claims one can do nearly 80% of the NASA checklists in emergency situations. That unfortunately means you have to read through lots of documentation before you know what buttons to push when - talking to the Shuttle's computer is a science on its own, the system was designed way before easy-to-parse displays were developed.




One scene showing the weirdness of spaceflight - the Shuttle is oriented upside-down, with Earth visible through the upper windows, and a manual is floating in mid-air. Closest I ever got to experiencing weightlessness in a simulation...




Let's get back down to Earth - these are impressions from a Bermuda abort landing after a simulated loss of two engines. Weather is somewhat shaky with a view on the runway only during late approach - but Bermuda is the only airport around that's big enough to take a Shuttle in.




During the late approach phase, the HUD provides most of the necessary guidance information...




... and gear is deployed rather late, only 300-600 ft above ground.




The Shuttle lands fast, touchdown is around 205 kt (if you manage...- aerodynamics gets tricky when airspeed drops) and Bermuda is just about long enough to come to a stop before running into the green.


So, that much for spaceflight - I'll try to show something else next time. Enjoy :)

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Thanks for the warm welcome!




So, when I don't fly the Shuttle into space, you can often see me in a helicopter. Generally I like having to do something when I fly, and the fidgety behavior of rotorcraft is exactly what does that - and I can explore the scenery and find a nice place to land. I often try how well I'd do with mountain rescue and such operations.


Here's an EC-135 in Norway, in the mountains around Bergen





I've added dynamical seasons to FG a while ago, so as one moves the slider, autumn colors gradually come in - decidous trees first get bright, then shed leaves, grass gets brown and the colors dull... in combination with snow, dust and wetness distributions, it allows you to give quite different moods to the same scene without having hundreds of extra texture sets.




Same helicopter, different location - this is Tenerife, the Teide volcano.




After I became interested in helicopters, I started to add all sorts of useful low-level flying visual cues because while for airliners five meter pixels are fine, trying to land a helicopter you'd like cm-scale details on the gfround - here's an example of the grass blades bending in the rotor wash, once you see that, you know it's not really far to the ground.




Here's Amelia, my co-pilot, to my knowledge the only animated co-pilot in Flightgear who can actually control the craft. I've introduced her since taking off helicopters is notoriously difficult for beginners, so learning to fly them is frustrating (I think I crashed 20 attempts before I got one into the air when learning it) - Amelia can be used as a flight instructor, taking off the Alouette-III and then in the air the user can request to take over.


Or she can hold a stable hover during a rescue operation while someone else operates the winch.




Here's a pet peeve of mine - the rope. It bugged me that we didn't have rope dynamics, so I spent three weeks coding a rope management class which does wind forces and acceleration-driven pendulum motion in the air - but the thing that really turned out difficult was the ground interaction - how the rope coils when you lower it, straighten when you drag it, change direction as you change direction during dragging it along... once you start to think about it, the possibilities are near endless, so the rope solver ended up quite computationally intensive in the end.


And it still can't handle uneven ground properly... but a friend of mine is working on the AirCrane, giving it the ability to move cargo or to stack elements (there's a video somewhere were he constructs a radio tower with it), so we decided we absolutely need better ropes for that kind of thing.



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And now to something completely different:





(Screenshot by Edward d'Auvergne)


While this looks straight out of a fantasy game, it's actually one of the more unusual 'aircraft' in FG - the dragon (she's a dragon girl by the way). While the exterior model is quite fantasy inspired, the flight dynamics is actually pretty serious - it's taken from a paper trying to reconstruct the flight of a Pterosaur - the dragon is an excellent soarer, slow to climb under windbeats, able to do tight turns in a thermal - and it can sweep wings and do a steep dive.


The background scenery is chosen for drama of course - it's one of the active volcanoes which I've recently introduced into the FG scenery, Kilauea on Hawaii.


I became involved with the dragon when we realized we didn't have any technology to properly animate the wingbeats of a living creature, so I volunteered to write custom GLSL shaders to do a smooth organic deformation of the vertex mesh (as you can see in this video).



(Video by Wayne Bragg)

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Occasionally I'm also found in single-prop GA aircraft - usually the Robin DR-400, but here I've chosen the C-182 - one of the aircraft where I'm often in contact with the maintainer to test new graphics effects.


In the first pic, you can see a fun project of mine - the bird swarm shader. Suddenly there's birds in the scenery, and they move around and flap their wings - it looks really cool, especially when you approach them with a slow plane like an ultralight.




This is why I spent months to research and code lighting during sunset - you look out and it's this incredible display of colors.




One of my pet peeves - differential lighting - note how the high cirrostratus clouds have a different color and are brighter, because the sunlight takes a shorter path through the atmosphere to reach them, and how the colors on the lower Cumulus clouds vary with their altitude. There's this incredible subtlety and richness in sunrise and sunset color - I've looked at pictures of hundreds of them (and have taken a collection of about a hundred interesting sunsets myself) - and they can be so different, yet so often beautiful in unexpected ways.





No wonder that for a while, sunset screenshots reliably won the FG monthly screenshot contest (in fact, I tried to compete with a cockpit-view shot, but eventually I caved in and submitted this, getting me a third place in the screenshot of the year 2016 contest...)



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Some impressions of Carrier Ops from FG's flagship, the Harry S. Truman













It's a really detailed 3d model, and it supports operation of the elevators so you can go to the hangar deck, there's wave motion which can make the landing more interesting, the deck shows rain splashes in bad weather...


I do enjoy doing carrier landings (mostly in the F-14) now and then, so I quite welcomed the addition of the highly detailed Truman model into the repository and did my part to equip the ship with a suite of modern effects.

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  • 1 month later...

Something I've been working on over the last days - Mie forward scattering of light at the fringe of opaque clouds (we've had it for transparent clouds for years now, but fringe scattering requires to move work to the fragment shader).




I'm ironing out some quirks still, but where it works, the contrast between dark cloud shadows and the silver lining and bright filaments looks quite stunning. It also makes for a rather interesting chiaroscuro for other more layered cloud types when the sun is behind those.

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Here's a rather dramatic shot taken while testing my current project - afternoon development of Cumulus clouds over Kauai (Hawaii) seen from ground level.




This combines quite a few features I like - the new rather dramatic contrast of Mie scattering and absorption in the clouds, the dark shadow the cloud casts onto the ground, turning the trees into dark outlines against the sky, the different vegetation layers on the ground giving the impression of a lush tropical island (and when you watch it in-sim, you can also see how the palm trees sway in the wind).


The fact that the ground is so rich and interesting contributes a lot to my joy in helicopter-flying... and Hawaii is one of our most beautiful sceneries (with lots of special attention by myself...)

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you have quite a varied repertoire in flight simulation.


Actually even outside flight. There's a whole collection of motorcycles and a few racetracks in the scenery where people do race competitions occasionally. Someone has build a Viking ship that sails plausibly with the winds. There's a couple of Star Treck atmosphere vehicles somewhere to be found. And there's a few scenarios for ground walking adventures.


I've not tried many of them - but generally this is what you get in OpenSource - people just do their crazy ideas...

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Just added to the repository: some of the weird rainbowy scattering on ice on the Cirrus clouds:






(Light scattering on ice is a rather rich topic, there's so many possibilities dependent on what types of ice crystals form... FG supports a few of them - the 22 deg ring, sundogs, the light pillar and the parhelic ring)

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Finally I realized how the ubiquitous velcro strips in the Shuttle need to be rendered to look 'furry'.




Here's another impression of my favourite spacecraft during the night portion of the orbit with the console lights on



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Some testing prior to the next Shuttle milestone release:


Beautiful early morning light over the Provence - the Shuttle landing at LeTube airbase (grass is still wet from dew...)











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  • 6 months later...

Some proximity OPS testing before the release of the next version of my favourite spacecraft:


Shuttle meets ISS - a relatively fast dusk flyaround maneuver. Orbital DAP to free (free drift, no automatic attitude management), establish a constant pitch rotation of 0.4 deg/s, use translational controls to keep ISS centered in COAS view recticle, use radar ranging to manage the distance and conpensate for centrifugal force, and we're slowly going around the station.


Actually it's a fairly busy maneuver at that speed... if there's enough time, it's done using the apparent rotation of the inertial frame with the local horizon, which is more like 0.06 deg/s.




Look at those clouds!




The station seen through the COAS recticle.




Last sunlight seen through the overhead windows.




And, as we rotate around, the lights of Paris above - or below, dependent on how your coordinate system is arranged :)



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