A preview of features for Flightgear 3.4

Flightgear is constantly under development and as the feature freeze for the next 3.2 release approaches, it is becoming increasingly clear what the next version will have to offer to users:

(to avoid misunderstandings – this is a selection of features currently under development and not a release note, i.e. there is no guarantee that all items will appear in 3.4, nor are the features of 3.4 limited to what is listed here)


Added realism for precipitation:

The precipitation system has been partially upgraded. The speed of falling raindrops now follows a physical scaling with droplet size, and the system renders now hail in addition to rain and snow. The correct dependence of lighting with illumination of the scene has been added. In Advanced Weather, droplet size and rain intensity are now set independently, allowing to realistically render fine spray as well as splattering rain in thunderstorms. A dynamical splash-pattern of raindrops added to the Atmospheric Light Scattering (ALS) runway effect completes the visual impression.

Advanced Weather clouds

Near photo-realistic 3d clouds:

The cloud rendering system has received an upgrade, allowing to let the edges of cloud patches gradually fade out. This makes several types of cloud formations appear even more realistic.


Have you ever wondered why the terrain appears bluish in the distance?

The Atmospheric Light Scattering (ALS) rendering framework has received a significant upgrade rendering the effects of Rayleigh scattering of light with air molecules and fine dust. This includes the in-scattering of light, resulting in the blue appearance of distant objects, as well as an out-scattering effect which makes colors seen through dry haze shifted towards the red. Combined with the already existing model for rendering hazes, this leads to truly impressive visuals.


Improved instruments:

A new flexible CDU framework allows aircraft developers to set up extensive CDU pages with relatively little effort. The framework supports both 3D and 2D instruments, multipages, down selecting settings to the scratchpad and various input formats (e.g. FL115 or 11500). It comes with a 2D panel popup screen so you won’t have to pan around the cockpit all the time. The CDU is expected to be introduced on the Boeing 747-400, but the framework has been designed to be flexible and fit other airliners.


Enjoy the latest additions:

The Extra 500 introduces a luxury aircraft one of the most advanced glass cockpits to be simulated by Flightgear. The F-14b has received a significant upgrade with an added JSBSim flight dynamics model. There is also progress on a new version of the X-15 which might make it into the release, as well as the F-20.

Atmospheric Light Scattering

Enjoy yet more interesting visuals:

ALS continues to receive a host of additions, allowing for some stunning visuals:

* tree shadows, rendered using a very performance-friendly technique
* landing and search lights for better night flight experience
* improved implementation of Fresnel scattering on water surfaces, leading to more realistic water appearance
* a procedural rock effect, capable of rendering a large variety of different rock textures and colors across the world

And many improvements more!

Much work is done under the hood which is not all visible:

* improvements to the rendering framework, leading to better performance
* more applications utilizing the FG-internal webserver
* a canvas-based alternative GUI and aircraft center, allowing to manage installed aircraft inside FG

Stay tuned as we fly towards our next release!

The F-14b is back

Ready to launch?

Thanks to Alexis Bory and Enrique Laso, the F-14b has been for a long time one of Flightgear’s most impressive 3d models, with a highly detailed cockpit and a large number of modeled systems.

But it just got even better – are you ready for a ride?

New flight dynamics

Richard Harrison has added a detailed JSBSim model for the flight dynamics based on a number of aerodynamical data sources which makes especially the behaviour at low airspeed very close to the real airplane. This also includes an accurate modeling of stall and departure into spin or flat spin and high alpha control reversal. Wing sweep can be controlled manually and affects the behaviour of the plane,

All of the plane’s control systems are implemented in JSBSim rather than in Nasal (which means they are computed at a much higher rate than the framerate), making the response of the plane more fluid, especially at framerates below 30 fps. All in all, the detailed JSBSim FDM adds quite a lot to the flight experience,

Improved systems modeling

The 3d cockpit has received a number of additions, among them a master warning panel with working indicators, an engine control panel and a master generator control panel. Other switches, such as the fuel cutoffs on the glareshield panel, are now functional, such that an engine startup/shutdown procedure from the cockpit is now possible.

Here is an example of the cockpit view in low-level flight:

And the RIO view:

The full range of operations

Just like the previous YaSim version, the new JSBSim F-14b supports a full range of military operations. The plane is fully aircraft-carrier capable (due to the improved modeling of low airspeed behaviour, carrier landings are somewhat more difficult than with the YaSim version though).

The plane also has a detailed radar with several different modes, capable of tracking targets, and the operation of the AIM-9M sidewinder missile is modeled as well as the M61A6 Vulcan gun.

Full air-to-air refueling capability from e.g. the KA-6 is also modeled:

Enjoy the new F-14b along with many exciting new features on current GIT (3.3) or with the forthcoming stable release 3.4!

(All features presented in the screenshots (bluish atmosphere haze, details on the Vinson flightdeck, improved appearance of water,…) are available in the current development version and will be part of the 3.4 release. The screenshots have been taken off the coast of Corsica and over Nevada, both in the default 2.0 World Scenery.)

Feedback on dds textures required

Should Flightgear switch to dds texture format?

What is this about?

The FG development team is considering to switch the format for terrain textures from png to dds. This would offer a number of significant advantages:

– dds is a compressed format, hence the download size of the FG base package may be decreased
– compressed dds can be directly used by many graphics cards, reducing also GPU memory consumption
– dds stores all texture resolution levels, i.e. no lower resolution levels have to be generated when the texture is used, hence it loads much faster into memory
– the resolution levels (‘mipmaps’) can be customized, allowing for some interesting effects at no performance cost

Practically all commercial simulations use dds for these reasons.

However, the dds compression algorithm is patented, which means that it is not readily available for OpenSource graphics drivers used by Linux distributions. Dependent on the specific hardware, this may or may not be a problem (modern graphics cards typically do not need the driver to process dds, for older graphics cards there are non-patented workarounds available which decompress the dds on the software level). The development team is concerned about making the Flightgear experience pleasant for all users, hence we would like to gather feedback how many users would be affected by a change in practice.

If there are no problems reported, FG will change defaults to txtures in dds format with the 3.4 release, and then phase out the use of png textures.

What would we need?

Flightgear already provides the simple option to test a dds texture set. If you are running on Linux and especially if you use an OpenSource graphics driver, please take 5 minutes to help during your next FG session:

– Open the dialog under View -> Rendering

– Under ‘Terrain texture scheme’, change the default ‘Region-specific’ to ‘Global alternative (DDS format)’ (see red circle)

– Press ‘Okay’ – FG will reload the terrain

– Do you see proper textures on the terrain (they may look different and may also not fit the location perfectly)? If yes, you’re fine. If you see monochromatic colors or other rendering artifacts, your system may have problems with dds.

– Change back to the texture scheme you like best

– Go to the wiki page and report your experiences, ideally including the graphics card you have and the driver you’re using.

Thanks for your time!

Some context for those interested

The visuals you get to see of the terrain in Flightgear depend on texture scheme and rendering scheme being used.

Simply put, the texture scheme selects a set of texture sheets which are mapped to the various landclasses in the terrain, such that a forest is rendered as forest rather than as grass. The old ‘Global’ texture scheme uses one such set everywhere in the world, the ‘Global alternative’ scheme uses a different set, but the format the textures are stored in is dds rather than png, and the ‘Regional’ scheme selects different textures based on what part of the world you are in. So the texture scheme selection governs things like the basic appearance of the terrain, the format the textures are internally stored in and the definitions where in the world certain textures should be used.

However, modern graphics cards allow to modify textures dynamically, or even create them on the fly by Procedural Texturing using shader effects. Dependent on shader quality level, these effects may have quite a pronounced impact on the visuals. If you are not running Rembrandt, you can switch the main rendering schemes runtime using the ‘Atmospheric Light Scattering’ (ALS) checkbox in the rendering dialog (blue circle in the image above) and explore what it does. So in summary, the rendering scheme selection governs just what is done in detail with the basic texture layers selected above (but, confusingly enough, shader effects may even replace textures).

Some examples exploring the different texture and rendering schemes below:

This is the South Rim of Grand Canyon using regional texture definitions and ALS procedural texturing:

Regional texture definitions allow to adjust the rock color to what is prevalent in the US Southwest, whereas the banded rock structure is not part of the texture file but generated procedurally.

Same scene using global texture definitions and ALS:

Using global textures, the rock and grass color is no longer adapted to the region, and also the shader effect no longer replaces the steepest forest patches by rock.

Same scene using global alternative (DDS) textures and ALS:

Switching to global DDS textures does not alter the visuals significantly in this case, the main difference is the texture format and detail resolution.

Same scene using regional textures and default rendering scheme:

The default rendering scheme at high quality contains some texture replacements which are coded globally into the effect framework and do not mesh too well with the regional texture colors seen elsewhere in the scene.

Same scene using global texture scheme and default rendering scheme:

Such global texture replacements in the shader however work better with a global texture scheme.

Same scene using global alternative DDS texture scheme and default rendering scheme:

Here, the dds texture scheme leads to somewhat different colors.

FG supports this wide variety of textures and rendering schemes so that users can customize the visuals to the performance offered by their computer and select the best compromise between good framerate and compelling visuals.

We need different schemes for this, since in trying to render a scene faithfully, we need to decide questions whether an average level of dust should already be included into textures (as done in the global scheme) or added dynamically according to weather (as done in the regional scheme in procedural texturing). The first alternative is preferable on low-end hardware where procedural texturing is too slow, but the second alternative works much better on high-end systems. Similarly, having different texture schemes allows us to provide a quick fallback for users who might experience problems with a dds-based scheme.

A preview of features for Flightgear 3.2

Flightgear is constantly under development and as the feature freeze for the next 3.2 release approaches, it is becoming increasingly clear what the next version will have to offer to users:


The Flightgear world is becoming more interesting…

A mission subsystem is being added. This allows to define tasks to be completed by a player which then receives points. Visual guidance symbols can be used to indicate the location of the next task. The mission system combines with the Milestone 4 release of the walker,and thus more complex adventures can be built in which the player has to exit an aircraft and walk to a certain location.

The walker subsystem now allows for more complex animated motion and adds NPCs, characters with whom a player can interact. Also, check out the selection of cars and motorbikes to explore the Flightgear world!

Cloud shadows

Finally some shade!

Cloud shadows are notoriously difficult to render, but for Advanced Weather in combination with the Atmospheric Light Scattering rendering framework, there is now an experimental option to add them (at least close to the aircraft) to the experience.


See the world from high up!

Introduced to provide better visuals for the spacecraft in Flightgear, Earthview is an alternative rendering engine intended for use at high altitudes. It renders Earth as a simple, textured sphere surrounded by a cloud sphere. The textures are provided by the NASA Visible Earth project. By default, a set of 2048×2048 textures is distributed, but Earthview is intended to allow easy access for users who want to install their own hires texture set. At full resolution of about 21000×21000 pixels per texture provided by NASA, it looks simply spectacular even from just 50 km altitude – see the Vostok capsule above entering the atmosphere.

Built-in http server

Access the property tree in a novel way!

Flightgear now includes the Mongoose web server as a httpd. This allows for interesting new application, for instance merging information from Flightgear and OpenStreetMap or Mapquest, leading to a new moving map application covering the whole world is available which tracks the airplane’s position.

Cloud drawing distance

See clouds out to the horizon!

Flightgear’s weather rendering so far has not been up to the task of showing a plausible view from high altitude. But this has now changed – a new framerate-friendly impostor technique is used to render clouds out to the horizon – wherever that may be (the system has been tested for 1000 km visibility from low Earth orbit).

Rendering improvements

Visuals keep getting better!

Lots of work has been done on the small details. New tree textures at higher resolutions make the forests actually look nice. Novel noise function are used to improve the visuals of snow on steep terrain slopes, to change tree height in discrete patches mimicking patterns of forest management, or to remove tiling artifacts from large-scale agriculture. Enjoy all the details the new version will have to offer.

And many improvements more!

Much work is done under the hood which is not obviously visible:

* The YASim flight dynamics engine is finally being developed further, with some long-standing bugs and limitations being addressed for the time being
* Ground interactions have been added to the JSBSim flight dynamics engine
* a new text-to-speech message is about to replace the old pre-recorded ATIS messages, adding a lot of flexibility
* an interface for allowing add-ons that use FSUIPC (an addon framework for Microsoft Flight Simulator) to talk to FlightGear
* osgEarth integration is still on the horizon

Stay tuned as we fly towards our next release!

Pushing the boundaries – the X-15 story

Suborbital flight with the X-15

Going to the edge of space… and back!

Operational history of the X-15

The North American X-15 was a rocket-powered, hypersonic research aircraft operated from 1959 to 1968 by the US Airforce and NASA. During that time, it set a number of records and greatly expanded the knowledge about conditions in the upper atmosphere and in hypersonic flight, thus ultimately laying the foundations upon which the Space Shuttle was built.

The X-15 reached Mach 6.72 on October 3, 1967, which is still today the official world record for the highest speed ever reached by a manned aircraft. In ballistic flight, it reached a top altitude of 354,200 feet (107.8 km) on August 22, 1963, crossing the boundary of space as defined by the Fédération Aéronautique International and making the X-15 the worlds first spaceplane. The 100 km altitude was only crossed on one other flight, but since the USAF defined the criterion for spaceflight by reaching an altitude of 50 miles, 13 different flights met this criterion and qualified the pilots for astronaut status.

Technical data

The X-15 is powered by the XLR-99 using ammonia and liquid oxygen as propellants, giving the plane a thrust of 70,400 lb and a thrust/weight ratio of 2.07. The rocket engine would only burn for about 80 seconds, the smallest part of the whole flight profile, but this would be sufficient to fling the plane on a high reaching ballistic trajectory or to accelerate it to tremendous velocities. It was the first man-rated rocket engine that could be throttled.

The plane has a thick wedge tail for stability at hypersonic flight conditions, however this produces a lot of drag at lower speeds. This means that the glide slope in the unpowered approach back to base is rather steep, and once back in the lower atmosphere, the X-15 sinks rapidly.

For maneuvering in the upper atmosphere where there is no significant air and the control surfaces do not work, the X-15 is equipped with a reaction control system (RCS) using hydrogen peroxide as propellant.

Flight dynamics of the X-15 in Flightgear is based on NASA-TN-D-2532 ‘Flight Measurements of Stability and Control Derivatives of the X-15 Research Airplane to a Mach Number of 6.02 and an Angle of Attack of 25 degrees’.

The RCS is not modeled in the default version of the X-15 available from the Flightgear download page, however an alternative versions of the X-15 with RCS and 3d cockpit are linked below.

Getting ready for suborbital flight

In reality, the X-15 was dropped from a B-52 aircraft at typically 45,000 ft and 450 kt, and then started its engines. This required a lot of preparation, however we also need to prepare the sim for suborbital flight.

Rendering suborbital flight is nothing Flightgear is designed to do, but as it is a very flexible framework, it can still be made to do it. The main problem is opening up the visibility to values which are plausible from the top of a ballistic arc at the edge of space, which amounts to about 400-600 km. This will require a modern graphics card and lots of system memory (the screenshots below were done on a GeForce GTX 670M with 3 GB GPU memory and another 8 GB system memory, this delivered a framerate of ~20 fps at arc top). Trying to open the visibility to large values can have severe performance impacts to the point that FG becomes unresponsive and can crash FG when memory actually runs out – it is recommended to try suitable settings with the ufo before using the X-15.

Some settings need to be tweaked:

* In order for the terrain to be loaded, the LOD range for terrain needs to be set. In the menu, View->Adjust LOD ranges, and set LOD bare to 500000 in order to allow terrain to be loaded up to 500 km distance.

* Loading terrain doesn’t help if the renderer does not display it. The camera of the renderer needs to be instructed not to clip faraway objects. Open the property browser from the Debug->Property Browser menu, and change into /sim/rendering/camera-group/ and adjust zfar to 500000 (or set the property at startup via commandline).

* Finally the weather system needs to be convinced to produce large visibility at high altitude. For Basic Weather, set the visibility at high altitude accrodingly in the mask. Advanced Weather will do it automatically if Max. Visibility in the Advanced Settings is high enough, however the gui doesn’t allow that, hence use the property browser again to set /local-weather/config/aux-max-vis-range to 13.12 (the slider operates on a log scale which is then converted to the actual value).

Switch randon objects, buildings and vegetation off before the flight – you won’t see them, and they will cost a lot of memory which you badly need otherwise. Launching over islands limits the amount of terrain to be loaded, also World Scenery 1.0 with low polygon count works better than he new World Scenery 2.0.

Finally, in the View->Rendering menu, switch Atmospheric Light Scattering on – this will render the atmosphere visuals.

One problem may be that FG can’t load the scenery fast enough. If the OS caches used files, loading the scenery from disk into memory once with an ufo-flight before using the X-15 may help here.

Climbing into space

Start the simulation in air, i.e. using commandline options –altitude=45000 and –vc=450 — this will produce the state of the X-15 just after having been dropped from a B-52. For a semi-historic trajectory, you can start above Nellis AFB (KLSV) and aim at a course of 240 deg which will roughly get you to Edwards AFB and Rogers Dry lake, the historic landing site for the X-15.

Take a few seconds after the drop to stabilize the plane into a shallow descent, double-check all settings and make sure you’re ready. If all looks well, push the throttle forward till the rocket engine ignites.

The XLR-99 delivers significant thrust, and speed will build up rapidly. We’re far too low for this, so pull gently on the stick till the plane goes into a 45 degree climb out of the lower atmosphere.

After a bit more than a minute, the main engine will cut out, but the X-15 will climb on. With increasing altitude, pressure based airspeed and altitude gauge become unreliable, so take a look at their inertial counterparts on the right side of the instrument panel now.

As the ballistic climb continues, the airfoils are losing effectiveness rapidly – time to switch on the RCS! Operate the BAL switch on the right side of the panel, press ‘i’ to grab the stick for RCS control (which in reality would be located on the left side of the cockpit). Think spacecraft now – there’s no damping force left, so operate the thrusters with carefully controlled bursts to stabilize the X-15. Once you have time to look out, you should see a lot of California. And Edwards AFB is really far, far down!

Back to Earth

Now comes the dangerous part — we’re falling down from 330.000 ft, we’re going to be really fast and the deceleration will be hard. The good news is that the view from the cockpit is now quite a bit more spectacular as the planet comes into view.

Stabilize the attitude using the RCS thrusters while high up. If the X-15 enters the atmosphere in a spin or roll condition, you will likely not survive the entry. As the plane gets lower, the airflow should start to build up, and if everything is going well, the X-15 should align its nose with the airflow.

The ailerons may become responsive below 200.000 ft already, start switching back to aerodynamical controls using the ‘u’ key and stabilize roll.

If you’ve been high up, the X-15 is falling really steeply at this point.

As the ground rushes closer, eventually the elevator becomes responsive as well, typically this starts below 80.000 ft. At this point, the plane will be going really fast and the ground approach rapidly. Pull back on the stick gently and watch the g-force. At this speed, even a gentle pull will translate into lots of force. Expect to experience 6-8 g during the pull out and prepare to black out in the worst phase. This is the most dangerous part of the flight.

Of course, if you don’t want to see a blackout simulated, you can always switch it off in the menu.

If everything went well, you should end up somewhere around 30.000 to 40.000 ft in level flight, with Edwards AFB (or whatever your landing site may be) in convenient reach. Now you can start trusting the pressure-based instrumentation again.

From this point, the drag of the stabilizing fins will be felt badly. Glide the plane maintaining about 300 kt. Rogers Dry Lake is a big place, so planning an approach should be reasonably easy.

Skids and gear out for the final approach…

… and a safe landing on the lakebed.

High speed profiles

Historically, the X-15 has not only been flown in high altitude profiles but also in high speed profiles. These are somewhat easier to pilot and control. For a high speed profile, aim at a more shallow climb angle, level off early and try to go horizontal around 100.000 ft, then let the X-15 accelerate and see how fast she will go.

After the engine cuts out, you can simply maintain altitude till the airspeed bleeds off and then slowly descent towards the landing site. Here’s an approach to Edwards AFB from a high speed run, coming in at 60.000 ft now.

Enjoy flying the first spaceplane mankind has built!

Alternative versions of the X-15

B-52 launched X-15 by Enrique Laso Leon (requires startup from historical location and joystick throttle control)

Free launched X-15 based on Enrique’s version, allowing startup at any location and keyboard throttle control, with some sound effects added.

Special thanks

The modelers of the X-15 in Flightgear:

Enrique Laso Leon
Jon S. Berndt

World Scenery 2.0

Together with the release of Flightgear 3.0, a new world-wide scenery is now made available!

Flightgear’s world scenery is based on large-scale processing of publicly available and GPL compatible geodata. There is practically no manual intervention involved, which means that the scenery team can’t decide what quality the scenery will have at a certain location, that is only determined by the quality of the available data.

Thanks to the efforts of developers in bringing the processing toolchain up to date, the new official scenery with much better resolution than the previous scenery has now been possible. The new scenery is already available via Terrasync, but it requires a recent version of Flightgear, older versions are not capable of handling the vertex number of the new terrain mesh.

This FlightGear World Scenery was compiled from:
– ViewFinderPanoramas elevation model by Jonathan de Ferranti
– VMap0 Ed.5 worldwide land cover
– CORINE land cover 2006v16 for Europe
– Several custom land cover enhancements
– The latest airports (2013.10), maintained by Robin Peel of X-Plane
– Line data by OpenStreetMap

In general, airport layouts are now improved and updated all over the world, major roads and rivers are drawn to much higher accuracy than previously and the elevation mesh resolution is increased everywhere.


The most stunning improvements are found in Europe, where in addition to the increased resolution of the elevation mesh, also the CORINE database provides high resolution landcover data. This makes the visuals both in mountain regions as well as plains much more applealing. Combined with regional texture schemes and procedural texturing, an almost photo-realistic effect can often be achieved.

Corsica, France seen from above in morning fog (utilizing Mediterranean texture scheme) :

Details of Corsica, France in low-level flight with the F-20:

Fjell lands in Norway (using Scandinavian texture scheme):

Norwegian fjordlands:

Ouside Europe

In the absence of CORINE data, improvements in the landcover rendering are not as dramatic, which leaves flat terrain largely comparable to the previous version of the scenery. However, mountainous regions benefit enormously from the improved elevation mesh resolution. The rendering of light and shade, transition shader effects and snow effects all key on elevation gradients and allow in essence to render the terrain with much more visual detail despite the lack of detailed landcover.

Desert hill chain near Tabas, Iran, seen from the ground (using Middle-East texture scheme and dust shader effect):

As above, seen from the air:

The Grand Canyon, USA (using dust shader effect):

View of the Grand Canyon, USA from high altitude:

Nanga Parbat, Himalaya, Pakistan seen across the Indus valley:

Himalaya north of Nanga Parbat:


Special thanks to the people involved:

John Holden
Olivier Jacq
Vic Marriott
Julien Nguyen
Gijs de Rooy
Christian Schmitt
Martin Spott
James Turner
Markus Metz
Pete Sadrozinski

A preview of features for Flightgear 3.0

Flightgear is constantly under development and as the feature freeze for the next 3.0 release approaches, it is becoming increasingly clear what the next version will have to offer to users:

Scenery 2.0

The next generation scenery has finally arrived!

After long years of waiting, a new version of the world-wide scenery shipped with Flightgear is now being rolled out. This scenery makes use of CORINE data in Europe, utilizes other custom enhancements elsewhere in the world, brings new and improved airport layouts and includes roads and other line data from the Open Street Map project. Especially in the CORINE covered regions, this leads to a much better visual appearance.

Novel water effects

Enjoy watching the shallows around tropical islands in fine weather!

At high quality levels of the water shader, a global water depth map is now used to change the water color in the shallow regions around islands and close to the coast. Especially in the Caribbean, this corresponds to a significant improvement in visual quality. The effect combines with the other variations in water color based on weather and base color due to algae or mud content.

The walker

Now you can get out of your airplane!

The walker project allows to leave an aircraft and explore the scenery on foot. This effectively allows adventure-game like scenarios in Flightgear such as The evil Graveyard where the walker also interacts with the scenery. Combined with the hires procedural terrain texturing options, you can start exploring the scenery from quite a different perspective and walk into your favourite virtual airport bar after a long and exhausting flight.

New airplanes

Enjoy a few new, highly detailed airplanes!

Some recent addition to the list of Flightgear aircraft, the new Boeing 707 (shown above) and the Robin DR400 Dauphin (a single propeller engine plane) impress with impressively detailed modelling of the cockpit, plenty of attention to realistic flight dynamics and especially in the case of the 707 a sometimes frustratingly realistic level of systems modelling.

More complex glass cockpits

Enjoy more realistic instruments!

The canvas 2d rendering technology allows the creation of more realistic glass cockpits with complicated instruments. Shown here is the new PFD and ND of the Boeing-747-400 as an example.

Phototexturing using osgEarth

Explore the scenery textured by aerial imagery!

An experimental implementation of generic phototextured terrain using osgEarth is now on the way and might make it into the 3.0 release. Once enabled, osgEarth renders the terrain scene by building the textured geometry at runtime from raw source imagery and elevation data. The input data can come from a variety of sources including web mapping services or local source data (e.g. geotiff) stored on disk. This feature is runtime-switchable from the default scenery rendering.

Better rendering of fog and haze

We take bad visibility seriously!

For some 3d applications, fog may just be a device to hide the terrain in the distance, but in Flightgear rendering fog and haze is taken quite seriously. The Atmospheric Light Scattering framework now comes with an improved way to render fog patches and variations in fog layer altitude, combined with even more impressive lighting of fog in low sun. You’ll never enjoy bad visibility this much!

And many improvements more…

And that’s not all:

* new regional textures for Scandinavia, Ascension Island and Corsica
* user-controlled moonlight effect for the Atmospheric Light Scattering framework
* added and improved airplanes
* more AI traffic/models

Stay tuned as we fly towards the next release!


The art of cloud and weather rendering

Author: Thorsten Renk

Advanced Weather

Advanced Weather is one of Flightgear’s two weather-generating systems. It operates based on a (limited) understanding of atmosphere physics – the user selects a weather situation, either from the menu or via specifying a METAR string, and the system simulates the weather from there. For instance, once the system knows how unstable the lowest layer of air is against convection, it automatically decides on the presence of thermals, turbulence, convective cloud number and visual appearance. In this way, generated weather matches cloud types in the different layers based on what would typically also occur in reality for the given weather situation.

The system renders practically all clouds in 3D. To get close to a real sky appearance, it utilizes a large variety of algorithms grouping cloudlets into layers, streaks or undulatus patterns. Combined with the ability to change the weather as a function of position, endless varieties of weather situations appear, and both in the online and offline weather modes, the sky never really looks the same.

Simply select a basic weather scenario and watch the cloud patterns change from high or low altitude!

Clouds and the terrain

Cloud layer placement in level terrain is a simple exercise, but to render weather properly in mountain areas is a challenge. The weather system continually receives information about the terrain surrounding the plane, from which the distribution of wind and turbulence close to the ground as well as the placement pattern of clouds is computed.

Try flying a mountain rescue helicopter in bad weather to see the weather system in action! Or simply go sightseeing in the mountains with a single-engine plane.

Precipitation and turbulence

Precipitation is rendered beneath overdeveloping Congestus and Cumulonimbus clouds as well as beneath layered clouds. Either via a METAR string or on the advanced options configuration tab, the outside temperature can be specified – and precipitation changes from rain into snow accordingly. Also on the configuration tab, the stability of the convective air layer can be determined. Try combining an unstable convective layer with stronger winds, and watch turbulence evolve and rugged clouds with strong vertical development appear, or select a very stable atmosphere and observe well-shaped, large Cumulus clouds evolve. Or try the thunderstorm scenario, and observe large Cumulonimbus clouds tower over the scene.

Using Environment shader effects, it is possible to add a snowline, wet terrain with gleaming puddles or drift ice into the scene – use this for best effect in rainy or snowy weather.

Try setting up a stormy scenario by adjusting the wind, and watch trees sway in the wind. Can you fly a helicopter in 30 kt winds and torrential rainfall?


Advanced Weather is fully interfaced with the Atmospheric Light Scattering rendering framework – which means clouds in low light get differential lighting according to altitude: While cloud bottoms of Cumulonimbus clouds may already be in shadow, cloud tops can still receive light. With the sun behind them, faint clouds glow in bright radiance whereas thick clouds show shadows, making for a beautiful play of light and shade.

The weather configuration tab also contains an air pollution effect – use this to see low light colors of sky and clouds change from clean air to smog.

Try an early morning takeoff before dawn, or flying into the night, and watch the low light illuminating the scene – there’s nothing quite as nice as a sunrise in the mountains.

Advanced Weather for Flightgear – made for pilots who love to watch clouds! All features shown will be available for the next official release!

A preview of novel features for the next release

Flightgear is constantly under development, and the current development version (2.11) contains already a number of interesting features beyond what 2.10 could do – so here is some (incomplete) list of what to expect from the next release:

Novel water effects

As part of the Atmospheric Light Scattering rendering scheme, some novel features have been added to the water shader:

Subtle variations in sea color and surface reflectivity are rendered at high quality, which together with slighly patchy fog improves the visual impression significantly. In addition, an experimental effect generating surf at some coastlines is under active development (coast of Lanai, Hawaii from the EC-135 cockpit).

The environment control allows to a drift ice overlay effect to render winter scenes in cold climate (coastline near Juneau, Alaska).

Improved usability

Flightgear becomes better accessible for the novel user:

A new tooltip system has been added, identifying knobs, gauges and levers for the new user and also indicating their value, thus eliminating the need to zoom to read badly visible instruments. On-screen messages are rendered in a new gnome-like semi-transparent window style. These changes are part of a larger restructuring of the user interface, which standardizes the interaction with cockpit clickspots and adds a more intuitive view mode by right-click/drag as option.


The Rembrandt rendering does shadows best, but this does not mean other frameworks can do nothing:

The balance of direct and indirect light has been re-adjusted to simulate the self-shading of terrain better. In clear weather, shaded surface are now rendered much darker, leading to much improved visuals in low morning or afternoon light (the B-1900D over the French Alps near Grenoble).

Air-air refueling

Fans of realistic air-air refueling will be happy:

The air to air refueling system has been much improved. It now contains a menu to select tanker type, speed and contact radius. Two new tanker planes have been added, and the contact points are now correctly specified, allowing for a much more realistic aerial refueling experience.

Ground texture resolution

Landing somewhere off an airport was never before this nice:

A high resolution shader effect has been added to the procedural terrain rendering of the Atmospheric Light Scattering framework, which renders cm-scale detail resolution. This allows for a much improved low level flight experience and more interesting helicopter operations in the terrain, as there are now visual markers available to gauge distance to the terrain (the EC-135 landing on Lanai shrubland).


The weather system has received a major upgrade. The grouping of sparse clouds into patterns is now much more realistic, replacing simple clusters by visually more interesting undulatus or wavy patterns.

As part of these changes, the rendering of low visibility scenes in Atmospheric Light Scattering has also been made more consistent.


The next version of a well-known aircraft arrives:

The Eurocopter EC-135 is currently undergoing a major overhaul. The FDM is completely revised, leading to a more stable experience in level flight, and the cockpit is done in high-resolution photorealistic texturing (over the French Alps, close to Grenoble).

A large selection of different models is provided, all with different liveries, equipment and slightly altered FDM (over the French Alps, close to Grenoble).


The environment becomes more interactive:

Canvas is a technology to render 2-d information into the scene – it can be used for complicated instruments or a HUD. However, it has now been extended to be applicable to scenery objects as well – this allows for novel features such as airliner docking guidance systems as shown here.

Seasonal effects

Now you don’t only have to fly in summer or winter:

As part of a restructured tree shader, deciduous trees now shed their foliage if they are above the snowline, thus they adapt to the shader-drawn snow effects better. In addition, Atmospheric Light Scattering includes now an experimental season effect (mostly tested for Europe) which allows to simulate the autumn coloring of deciduous forests and pastures.

And many improvements more…

And that’s not all:

* regional textures for Middle East, the UK, Greenland, Indonesia, the arctic sea and Madagascar have been added
* improved aircraft checklists
* better interface between Basic Weather and Atmospheric Light Scattering rendering
* tree movement in the wind
* novel animations, allowing e.g. for more realistic rendering of complex gear motion


Stay tuned as we fly towards the next release!

Fly Hawaii!

Author: Thorsten Renk

Destination Hawaii

One of the first places available as hires scenery in Flightgear, and also among the first places to receive a dedicated regional texture scheme, the island chain of Hawaii is a very spectacular destination in the Flightgear world. It offers a compelling variety of terrain from dry and barren lava plains to lush tropical rainforest, from the gentle fertile plains to rugged mountains and steep cliffs towering over the sea and from the densely populated island of Oahu to uninhabited Kaho’olawe.

Flying Hawaii can be easy or challenging – there are busy international airports and lone airstrips in remote locations, the altitude of the terrain ranges from sea level all the way up to Mauna Kea towering at 13,796 ft and steep gorges cut into the lava cliffs allow for tricky helicopter excursions.

Currently the scenery is only available via TerraSync and not by direct download from the website, presumably this will change with the next release of world scenery. While the release preparations for Flightgear 2.10 are underway, this article provides a first glimpse into some stunning new features which are currently being developed for the 3.0 release in summer 2013 – high resolution terrain texturing for closeup scenes.

Aeronautical charts for the whole of Hawaii are available online at skyvector.com, see for instance here for all charts relevant for Honolulu International Airport.

Hawaii ‘Big Island’

With a total area of 4,028 square miles, Hawaii is by far the biggest island of the archipelago, exceeding the size of all other islands taken together. It is also the youngest of all islands, dominated by the gentle rising cones of the five massive shield volcanoes Kohala, Mauna Kea, Hualalai, Mauna Loa and Kilauea, with the last two still being active.

The central part of the island is occupied by the twin cones of Mauna Kea (foreground) and Mauna Loa (background) which both reach above 13,000 ft and consists of extended lava fields, while the coastal region is somewhat more fertile.

The first destination reached however when arriving from the Honolulu region is Upolu Point, a region of eroded volcanic rock and spectacular gorges.

A flight to Hilo, the main city of the island, can pass between the two major shield volcanoes and requires a climb from sea level to more than 7,000 ft, which requires some adjustment of the mixture in a single-engine propeller plane. The climb to the pass is mainly above arid grasslands.

At higher altitudes, the spectacular lava fields of Mauna Loa dominate the scene.

Here is yet another view on Mauna Kea from the pass – often the volcanoes reach above the cloud layer.

Seen from the pass, Hilo seems close, but the slope of the terrain is so gentle that it is very easy to underestimate the true distance. Towards the coast, forests and fertile ground dominate the scene again.


Maui is perhaps the island with the most diverse terrain. Its eastern part is dominated by the mighty cone of Haleakala, reaching just above 10,000 ft. The middle part is a fertile valley, whereas the western part features the rugged West Maui Mountains, which are considerably lower than Haleakala, but certainly make up for that with steep cliffs and deeply cut valleys.

Since the prevailing winds come from the northern side, air rises on the flanks of Haleakala, leading to fertile and overgrown northern slopes, whereas the southern slopes of Haleakala look completely different and show rather different weather.

Flightgear’s Advanced Weather is actually capable of simulating the resulting distribution of clouds from this effect – in fact, Haleakala has been an inportant test case in the development of the weather system.

Closely grouped in the vicinity of Maui are also the islands Lanai, Molokai and Kaho’olawe, easy to see in clear weather, thus Maui is an ideal starting point for island-hopping adventures.

Approaching from east, the scenery is dominated by Haleakala, here the more arid southern slopes are seen.

Maui is substantially older than Hawaii island, and so the volcano has started to erode quite significantly when compared to Mauna Loa – as a result, the fertile land extends much higher up. Haleakala crater however remains a rather impressive sight.

When approaching from the west, the cliffs and gorges of the West Maui Mountains are the first feature to become apparent.

On a clear day, the surrounding islands (here Molokai in the background) can clearly be seen:

The West Maui Mountains themselves contain quite some impressive sights – it is especially worthwhile to explore the various canyons and cliffs with a helicopter.

Yet another flyby view from the F-14b RIO position on the West Maui Mountains:


Going west, the geological age of the island chain increases, and thus terrain features become more gentle as the volcanic rock erodes and changes into fertile soil. The island of Oahu is where the majority of the Hawaiian population lives and where the capital Honolulu is located. This is also where Honolulu International Airport, the most busy of all Hawaiian airports is found, and the home of famous sights as Pearl Harbour. Honolulu was envisioned as an emergency landing site for the space shuttle, and in fact the ‘reef runway’ (shared, as the rest of the airfield, with Hickam Air Force Base) used to be designated for this purpose.

Oahu stretches between two mountain ridges, which rise up to an elevation of just over 4000 ft. Here is a view of the island from the west.

Central Oahu is flat and largely in agricultural use. In the background, Honolulu and Pearl Harbour can be seen.

One of the most scenic spots on the island is Kailua beach on the north-eastern coast, offering a spectacular constrast of steep cliffs, long beaches and lush tropical vegetation.

The hires ground texturing scheme for Oahu has been carefully designed to display the contrast between lush vegetation and the red volcanic soil.

The other islands – Lanai, Molokai, Kauai, Kaho’Olawe and Niihau

Lanai is a fairly arid and sparsely populated island south-west of Maui with a single airport. It is dominated by a single mountain ridge reaching just above 3000 ft, with some valleys carved by erosion.

Molokai is, like Maui, a fairly diverse island – its eastern part consists of steep and towering cliffs whereas its western part is mostly flat and gentle landscape. Kalaupapa airport (PHLU) is built on a peninsula just beneath the cliff faces.

Kaho’Olawe is a small, uninhabited island. It has no airport and can only be reached by helicopter.

Its surface is mostly composed of arid stretches and lava fields.

Kauai, the garden island, is one of the nicest bits of scenery in the Hawaiian islands. It features the spectacular Na’Pali coast and Waimea Canyon.

Sadly, the scenery in Flightgear is currently a bit of a let-down – the terrain shows some errors in Kauai, and neither the Na’Pali coast nor Waimea come anywhere close to the originals.

Here is a scene close to Hanalei:

Finally, the island of Niihau is not part of the high resolution scenery package, and thus not really worth visiting.

Some Hawaiian airports

Hilo International Airport (PHTO) is located on the eastern side of Hawaii island at the coast – in a vert scenic location close to the town of Hilo. It is one of the two major airports of the archipelago and with a runway length of 9,800 ft large enough to admit essentially all airplanes.

Kona International Airport (PHKO) is located in the lava fields at the western coast of Hawaii island. Three million pounds of dynamite have been used to flatten the lava flow on which it was constructed. It offers a single 11,000 ft runway which is second in length only to Honolulu International Airport.

Waimea-Kohala Airport (PHMU) is a not very busy public airfield at 2,600 ft altitude in the western drylands of Hawaii island. It offers a single 5,197 ft runway.

Princeville: (HI01) is a small private airport close to Hanalei on the garden island Kauai. It is only suitable for smaller aircraft.

Lihue: (PHLI) is the main airport of Kauai. It has mainly connections to Honolulu, but also some long-distance traffic to the US mainland.