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{{See also|Flying on other planets}} | {{See also|Flying on other planets}} | ||
The default FlightGear terrain rendering strategy is designed for visuals from aircraft cruise altitude. While it is [http://www.flightgear.org/tours/pushing-the-boundaries-the-x-15-story/ possible] to use it for altitudes up to some 100 km, the performance impact becomes increasingly prohibitive and the visuals are not overly compelling. In particular for orbiting spacecraft such as [[Vostok-1]] or the [[Space Shuttle]] neither rendering nor loading the standard terrain mesh is fast enough. | |||
Earthview is an alternative orbital rendering engine for FlightGear designed to get credible visuals in these situations. It is based on projecting a simple textured sphere representing Earth into the scene using ray optics. The quality of the terrain visuals then largely depend on the texture size used. Since there is then only a single object in the field of view, performance is generally very good provided that there is enough texture memory available. | |||
{{Spaceflight}} | {{Spaceflight}} | ||
=== | === Overview === | ||
Earthview is started from the menu as View -> Earthview Orbital Rendering. This brings up the configuration dialog. | |||
[[File:Earthview.jpg|thumb|Earthview configuration dialog]] | |||
The options checkboxes allow to select | |||
* whether a cloud layer should be rendered above the planet | |||
* whether the cloud layer information should be used to render cloud shadows onto the terrain | |||
* whether Earthview should take control of the atmosphere visuals and adjust them based on altitude | |||
* whether textures should be procedurally enhanced with overlay textures to provide better apparent texture resolution | |||
'Start' run Earthview, 'Stop' ends the computations and removes the 3d model. Generally, using Earthview below an altitude of ~30 km / 100.000 ft is not recommended and will almost certainly not give the desired visuals. | |||
Sliders further down can be used to adjust details. For instance, if no cloud shadows are rendered, it is possible to rotate the cloud sphere around Earth and give different places different weather (otherwise, the cloud pattern will always be the same, i.e. if a place is obscured by clouds initially, it will always be). Using Rayleigh, Mie and Density, atmosphere visuals (if Atmospheric light scattering] (ALS) is on) can be adjusted. Visibility dials the amount of fogging seen on the planet. | |||
Earthview runs without ALS, but does not provide any credible visuals of the Atmosphere. | |||
If atmosphere visuals are rendered, Earthview interacts with the weather system in that the visibility used by Earthview and by the weather system will be the same. In the case of [[A local weather system | Advanced Weather]] (AW) this is an issue because both systems try to adjust atmosphere visuals. For this reason, AW needs to be ended before Earthview is started. There is no general option to do this automatically, but an automatic transition from default FG rendering and weather to Earthview is easily coded spacecraft side and implemented for the Space Shuttle. | |||
All textures are taken from the [http://visibleearth.nasa.gov/ NASA Visible Earth project] - at the highest resolution level, Earth can be rendered at 32768x65536 pixel (about 500 x 500 m per pixel) and clouds with half of that. Currently there is a much lower texture resolution distributed in FGData as the highest resolution set has eight textures sheets of 172 MB each which would double the current repository size. It is however easily possible to obtain the textures from the NASA website and apply them. | |||
At highest texture resolution, visuals are generally very compelling: | |||
[[File:Earthview for low Earth orbit.jpg|450px|Low orbit]] [[File:Earthview hig altitude.jpg|450px|High orbit]] | [[File:Earthview for low Earth orbit.jpg|450px|Low orbit]] [[File:Earthview hig altitude.jpg|450px|High orbit]] | ||
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[[File:Earthview cloud shadows.jpg|450px|Cloud shadows in Earthview]] [[File:Earthview specular water reflections.jpg|450px|Specular water reflections and cloud shadows in Earthview]] | [[File:Earthview cloud shadows.jpg|450px|Cloud shadows in Earthview]] [[File:Earthview specular water reflections.jpg|450px|Specular water reflections and cloud shadows in Earthview]] | ||
Earthview can also render Aurora Borealis seen from space. | |||
Earthview | |||
== Requirements == | == Requirements == | ||