Sky model – Defines which sky model to use. The default choise of PRG Clear Sky model is the most physically accurate and works best in most scenes. There are 3 more different Sky models: Preetham et.al, Rawa-Fake, Hosek & Wilkie.
Intensity – Overall intensity multiplier of the sky. Default value of 1.0 produces physically accurate result.
Turbidity – The amount of pollutants (smog) in the atmosphere. Increasing the value makes the sky more hazy, while decreasing it makes the sky clearer.
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"PRG Clear Sky" model has a valid range of turbidity between 1.81 and 4.89 (values outside of this interval are clamped).
Fake horizon blur – How much the sharp horizon line is bluerred. This simulates aerial perspective.
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There is no need to use this fake blur with the PRG Clear Sky model, since it already has physically correct blur, which can be controlled by the altitude parameter.
Improved model
Altitude – Observer altitude in meters. With higher values the sky gets clearer and the horizon line less sharp.
Volume effect – Enables volumetric effect based on the atmospheric settings from this sky map.
Scale – Scales the atmospheric volume effect. Increasing this value will lead to the increase of density of the volume and thus to more pronounced volume effect.
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Only the value of 1 is realistic in a scene with correct scale.
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Only one such atmospheric volumetric effect will be used at any given time, even if multiple sky maps are present in the scene.
Alpha mode – Specifies how the volume effect is visible in the alpha channel. Available modes are:
Default – This is the default mode. In this mode, the volume effect alpha value is derived from its opacity. Always black – In this mode, the volume effect alpha value is black (it shows as transparent). Always white – In this mode, the volume effect alpha value is white (it shows as opaque).
Sun Selection –Allows to select which mode to use-:
Automatic – To compute sky texture value, we need to know the sun's position in the sky. Automatic mode selects the sun object in the scene automatically. Manual mode allows the user to selects the sun object in the scene automatically.
Manual – Allows the user to select the sun object manually.
Ground
Color – The constant color used for the ground under the sky. The sky itself is affected by this value near the horizon.
Affected by sky – When enabled, the ground color is assumed to be the input diffuse color of the ground material, which is multiplied by the sky irradiance. When diasabled, the ground color is the final color returned by the texture for low angles, regardless of the sky.
