Editing FlightGear (section)

=== Rendering and visual cues ===

==== Atmosphere rendering ====
''Flightgear's'' atmospheric rendering is able to provide constantly changing visual cues of processes affecting atmospheric fluid flow and their likely evolution and history - to make prediction of conditions ahead or when returning at a later time possible. Simulation of directional [[Atmospheric optics|light scattering]] by the Advanced Light Scattering framework in the atmosphere shows the 3d distribution, layering, geometry, and even [[Sun dog#Formation and characteristics|statistical orientation]] of particles in different [[Scattering#Electromagnetics|scattering regimes]] like Mie or Rayleigh. This ranges from different moisture droplets, to smog, to [[Ice crystals|ice crystals of different geometry]] in clouds or halos.<ref name=":232"/><ref name=":022"/><ref name=":1">{{Cite web|title=FlightSim.Com - FlightGear's Atmospheric Light Scattering Rendering Framework|url=https://www.flightsim.com/vbfs/content.php?16990-FlightGear-s-Atmospheric-Light-Scattering-Rendering-Framework|url-status=live|archive-url=https://web.archive.org/web/20210315105803/https://www.flightsim.com/vbfs/content.php?16990-FlightGear-s-Atmospheric-Light-Scattering-Rendering-Framework|archive-date=15 March 2021|access-date=2021-03-15|website=FlightSim.Com|at=See pages 1 to 6}}</ref><ref name=":2">{{Cite web|title=FlightSim.Com - Weather in FlightGear--|url=https://www.flightsim.com/vbfs/content.php?18201-Weather-in-FlightGear/view/2|url-status=live|archive-url=https://web.archive.org/web/20210315112815/https://www.flightsim.com/vbfs/content.php?18201-Weather-in-FlightGear|archive-date=15 March 2021|access-date=2021-03-15|website=www.flightsim.com|at=See pages 1 to 3}}</ref>

===== Cloud rendering =====
The 3d density distribution of cloud (or [[Condensation Trail|condensation trail]]) moisture rendered by ''FlightGear'' acts as a cue to the corresponding 3d structure of fluid flow, such as the [[:File:Typical Lifecycle of a Single Cell Thunderstorm.png|up and down draft]] loop of storm cell, [[internal gravity waves]] forming [[Wave cloud|undulating cloud bands]] signalling a sweeping cold front, or windshear [[Cirrus cloud#Formation|shaping]] cirrus clouds at higher altitude.<ref name=":022" /><ref name=":232" /><ref name=":03"/><ref name=":1" /><ref name=":2" />

===== Precipitation and accumulation rendering =====
''FlightGear'' is able to render rain falling from specific clouds in rain volumes containing the correct droplet size to determine the properties like thickness and intensity of rainbows.<ref name=":022" /><ref name=":32"/><ref name=":2" /> Perceptual phenomena like rain streaks are rendered with streak length shortening as time is slowed. Rain and water spray streaks on canopy glass provides cues to the relative air flow, while frost and fog with correct light scattering provide cues to temperature.<ref>{{Cite web|last=|first=|date=December 7, 2015|title=The new Cessna 172p – FlightGear Flight Simulator|url=https://www.flightgear.org/tours/the-new-cessna-172p/|url-status=live|archive-url=https://web.archive.org/web/20201205093411/https://www.flightgear.org/tours/the-new-cessna-172p/|archive-date=5 December 2020|access-date=2019-08-31|website=FlightGear.org|language=en-US}}</ref><ref name=":1" /><ref name=":2" />

''FlightGear'' is able to render specified historical accumulation levels of water and snow accounting for flatness on the surfaces of for both terrain and buildings. This provides cues to surface moisture or friction, and weather driven by surface heating that reduces with snow thickness. ''FlightGear'' can render gradual snow and ice cover on inland and ocean water.<ref name=":022" /><ref name=":2" />

===== Hazes and Halos =====
Layering of hazes is rendered by ''FlightGear'', such as low lying [[Haze|ground haze]] with 3d structure, smog related to human activity, and dust. ''FlightGear'' renders various [[Halo (optical phenomenon)|halos]] due to ice crystals in the atmosphere, or due to Mie scattering in fog by artificial lights such as landing lights.<ref name=":232" /><ref name=":1" />

===== Orbital rendering =====
''FlightGear'' is able to render day/night visuals of Earth from orbit at high detail with scattering due to clouds, dust, and moisture, as well as effects such as lightning illuminating storm cells. Orientation cues in cockpit are provided by changing colour of light from Sun, Earth, and Moon for craft such as the Space Shuttle. The gradual transition in lighting for spacecraft, between upper and lower atmosphere regimes, is handled by dedicated rendering code. Auroras are simulated with varying intensity and varying penetration of magnetic flux tubes into the atmosphere. They are visible from both space and ground.<ref name=":732" /><ref name=":4">{{Cite web|last=|first=|date=August 26, 2018|title=The Grand View – FlightGear Flight Simulator|url=https://www.flightgear.org/tours/the-grand-view/|url-status=live|archive-url=https://web.archive.org/web/20201205091017/https://www.flightgear.org/tours/the-grand-view/|archive-date=5 December 2020|access-date=2019-08-31|website=FlightGear.org|language=en-US}}</ref><ref name=":1" />

Accurate rendering of planets, moons, and stars with correct phases/brightness based on ''FlightGear''<nowiki/>'s celestial simulation allows cues or data for [[celestial navigation]] - without reliance on vulnerable ground aids, including of pre-GPS era craft. The celestial simulation allows craft such as the Space Shuttle<ref name=":732" /><ref>{{Cite web|title=FlightSim.Com - FlightGear - Visiting the ISS|url=https://www.flightsim.com/vbfs/content.php?19086-FlightGear-Visiting-the-ISS|access-date=2021-03-15|website=FlightSim.Com}}</ref> to use [[star tracker]] instruments.

===== Environment rendering =====
''Flightgear''<nowiki/>'s Advanced Light Scattering framework simulates locations in time as well as space. The environment simulation renders seasonal change as leaves of different species of trees, bushes, and grass change colour or fall.<ref>{{Cite web|last=|first=|date=February 21, 2015|title=Simulating the ever-changing scenery – FlightGear Flight Simulator|url=https://www.flightgear.org/tours/simulating-the-ever-changing-scenery/|url-status=live|archive-url=https://web.archive.org/web/20201205083451/https://www.flightgear.org/tours/simulating-the-ever-changing-scenery/|archive-date=5 December 2020|access-date=2019-08-31|website=FlightGear.org|language=en-US}}</ref> Simulated swaying of grass, trees and windsocks provide cues to processes changing the windfield near the ground, while wave simulation provides cues near water.<ref name=":232" /><ref name=":022" /><ref name=":2" /> Cloud shadows and the general state of the atmosphere affect light traveling to each point of the environment and then traveling in the atmosphere to reach the eye - the cloud setup and particle spread in the atmosphere changes the colour of the light cast on the environment.<ref name=":232" /> Water colour therefore changes based on atmosphere overhead, and also depends on water impurites in a region. ''FlightGear'' is capable of rendering a variety of [[Types of volcanic eruptions|volcanic activity]] of different intensity that, from v2019.2, responds to the windfield, as well as smoke.

The combination of rendering of the state of atmospheric processes, Aurora, simulation of celestial bodies, ground accumulation of rain or snow or dust, ice cover of water, and the environment simulation produces visualisations with a vast number of permutations.<ref name=":232" /><ref name=":022" /><ref name=":4" /><ref name=":1" />