This model is supposed to represent the color gradient at the horizon, depending on the sun location and the observer altitude, up to 60 km (since atmospheric layers above 60 km are not modeled).
Sun Size and
Sun Intensity determine the size and brightness of the Sun disk shown in the rendering. They also affect how the scene is illuminated. Default values are ok. The Sun disk can be hidden by unchecking
Sun Disk option.
Then the Sun elevation above the horizon and azimuth are entered in
Sun Elevation and
Sun Rotation. The altitude of the observer in meters is entered in
Finally the quantity of light can be scaled using the value of
Strength. The default value is way too large, a better value is 0.06.
Ozone can be used to tune the physics of the model, but unless there is a good reason for changing them, the default values should be kept.
Here is a view from a fisheye, looking at South (
-Y direction), with the sun on the left side (not in the field of view):
Looking at South, with the sun rising on the left
The same scene, but looking at East:
Looking at the rising sun
The position of the sun, 4° elevation and 85° azimuth, corresponds to today at 6:00 UTC, for an observer at latitude 45° and longitude 0°. This site provides both elevation and azimuth for any observer at any time.
The scene is indeed dark, but the texture seems to behave correctly, and is ok when the sun is repositioned to correspond to times from 7:00 to noon, with the elevation gradually increasing to 51°. After noon the behavior is reversed as other factors like air temperature are not modeled.
Looking at South, at an hour interval until 12:00