Legacy Atmosphere

DEPRECATED. This shader is unsupported, but it may still get installed with Softimage to provide compatibility with older scenes that use it. It is recommended that you replace unsupported shaders in your scenes with equivalent shaders from the current Softimage shader library.

Shader Type: Environment (Legacy)

Output: Color (RGB) value

Acts as a planet-atmosphere simulator. It uses advanced numerical techniques to simulate the scattering that light undergoes when traveling through an atmosphere. This makes it possible to simulate both a view of a planet from outer space and an outside view of the planet's surface.

NoteNo render tree connections are possible with this shader.

Global

Global Parameters

Inclination, Azimuth	Determines the position of the point of view relative to the planet's center. The direction is given as Inclination and Azimuth.
View Altitude	The default value is 1.8 m above the surface (about where a tall person's eyes are). There's an important difference between the viewpoint in the shader and the real viewpoint in the scene. This viewpoint (the shader's) determines how the environment shader looks, and the position of the camera within the scene has no effect on that. You can place the viewpoint outside the atmosphere, resulting in an extraplanetary view, by giving an altitude of, e.g., 100 km and using the default parameters, pointing the camera downward.
Planet Radius	The default value is 6 000 000 m (approximately equal to the Earth's radius).
View Gain	Controls the overall brightness of the image. With the Automatic Gain Control checkbox unchecked, this is an overall scaling factor.
Automatic Gain	Causes the brightness of the environment to be scaled in such a way that the ground directly under the viewpoint has the illumination of that specified in "view gain." This is very useful for daylight scenes, where you might put a ground map on and you want it to be properly illuminated.

Atmosphere

Atmosphere Parameters

Thickness	Scale thickness of the atmosphere. The default value is 7400 m (the thickness of the Earth's atmosphere if its density were uniform).
Density	Scale thickness of the atmosphere. Modifying it affects the color of the sky and the sunset.
Dust Thickness	A smaller sphere of dust is a part of the atmosphere. Defines the height of the dust.
Dust Density	The density of the dust. The dust makes a gray-colored haze appear. It will make a very effective halo around the sun as well. You may want to set this to 0 for Arctic clarity of the air. When it is set high, the sun will no longer be discernible from the glare.
Samples	The shader works by integrating the air density over a number of invisible sample spheres in the atmosphere. This controls their number. High values (like 20) give more accurate results but take longer rendering. Low values can be very adequate, but it depends on the view position. Keep it as low as you can until you are satisfied with the results.

Ground

Ground Parameters

Spherical Mapping	Useful for extraplanetary scenes, where you can map a geographical map on the planet using the traditional spherical mapping with two pinch points at the poles. When this mapping type is selected, the scaling is no longer in kilometers and a scaling of 1 means that the map will stretch once around the planet.
Lollipop Mapping	Similar to cloud mapping and is useful for ground scenes where you could place a map on the ground.

Transformations

X, Y Scaling	The scaling of the map. In lollipop mode, it states how many kilometers each instance of the map should stretch. In spherical mode, it determines how often the map wraps around the planet.
Rotation	A rotation of the map
X, Y Translation	The translation of the map. The same difference between the modes applies here as with the scale parameter.

Cloud

Cloud Parameters

Cloud Color	The color of the clouds. Mars has red ones, we like white ones (unless you live in the UK, where they're "gray").
Turbulence	Creates a more turbulent-looking cloud fractal.
Altitude	Places the cloud plane in the atmosphere model; 500 m is about right.
Amplitude	Defines the cloud fractal's amplitude.
Ratio	The fractal ratio; a value of 0.707 works well.
Iterations	Clouds are soft so few iterations are necessary.
Center Position	This is the center (expected value) of the fractal. 0 = no cloud; 1 = full cloud. This parameter is really a balance control between the two extremes and works with the Amplitude in placing the fractal in the 0..1 domain.
Animate	When on, the clouds become animatable with the time parameter.
Animation Speed	Only on once you select the Animate option. Defines the speed of the animation.

Transformations

X, Y Scaling	The clouds are placed on the planet using a lollipop mapping. This means that there will be stretching and a seam at the South pole (negative Y direction). Scaling is in kilometers for convenience, so that a scaling of 1 will give the clouds largest features 1-km diameter.
Rotation	Rotates the fractal; can be useful for eliminating visual artifacts due to repetitiveness in the fractal.
X, Y Translation	Offsets the cloud fractal; can be animated to produce a wind effect.

Star

Star Parameters

Density	Defines how much of the sky is occupied with stars.
Bias	A bias on the random brightness distribution.
Brightness	Scales the brightness of the stars. Sometimes they are too faint and have to be scaled to become visible.
Saturation	The color saturation of the stars. They have random colors which can be made visible by increasing the saturation.
Variation	Controls how much the brightness varies with time.
Twinkle	The time with which the star's brightness varies.

Transformations

X, Y Scaling	A scaling factor for the stars.
Rotation	Rotates the stars about the azimuth.
X, Y Translation	An offset factor for the stars.

Moon

Moon Parameters

Color	The color of the moon. This is really the diffuse reflectivity of the moon, which is modeled as a ball. Our moon is really a rather dark object that only appears bright at night because the sun is so much brighter than the night.
Size	The size of the moon in degrees. From Earth, the sun and the moon look roughly the same size.
Halo Size	Makes a halo around the moon. Good for simulating a frosty night.
Inclination	The deviation from vertical of the moon's center.
Azimuth	The azimuth direction of the moon.

Sun

Sun Parameters

Color	The color of the sun. Our sun is very close to white and that is a useful approximation. However, there is nothing stopping you from making it green. This, of course, will make the whole scene green.
Intensity	A scaling factor of the sun's color. Because the sun is vastly more luminous than any other celestial body, you must be able to control its color with ease and have it powerful at the same time. The default of 10 is very conservative, relative to the real world.
Attenuation	Attenuates the apparent brightness of the sun when it is visible in the shader. The sun itself is usually much brighter than any other object in the scene. If you want it to appear dimmer, try setting the attenuation to 0.5 - 0.99 when creating a sunset scene; be careful, though, if you have a high dust density, because the brightness of the scattered light of the dust will quickly swamp the sun. It may be better simply to scale the scene's overall brightness for the sunset effect.
Size	The size of the sun disk in degrees. The real sun is very small, so the default value of 5 is slightly exaggerated.
Halo Size	Makes it possible to make the edges of the sun appear more fuzzy if the dust-produced halo is not sufficient.
Inclination	Defines how many degrees from the vertical the sun's center is located.
Azimuth	Positions the sun in the X-Z plane. 0 is in the X direction; 90 is in the positive Z direction.

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