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.
| Atmosphere | Ground | Cloud | Star | Moon | Sun | Sun
Material (Soft3D)
Output: Color (RGB) value
Uses advanced numerical techniques to simulate scattered light traveling through an atmosphere. You can simulate a view of
a planet from outer space and an outside view of the planet's surface.
The basic model is a colored sphere (the planet) surrounded by a uniform atmosphere of exponentially decreasing density with
altitude. This atmosphere fosters a type of light scattering, known as Raleigh scattering, and is what makes the sky blue.
Within this atmosphere is a smaller sphere of dust (and water droplets), in which Mie scattering occurs. This scattering is
what makes the hazy panoramas that are common in the tropics. Suspended in the atmosphere is a thin layer of fractal clouds.
Outside the atmosphere, infinitely far away, is a backdrop of stars and a moon. And of course, there is a sun. In this shader,
the sun is visible, both as a virtual light source (but it won't illuminate the objects in the scene) and when directly viewed.
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The shader's name. Enter any name you like, or leave the default.
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Global
Global Parameters
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These parameters determine the position of the point of view relative to the planet's center. The direction is given as Inclination
and Azimuth.
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The default value is 1.8 m above the surface; this corresponds to a tall person's eyes. It is important to understand the difference between the viewpoint in the shader and the real viewpoint in the scene. This
viewpoint determines how the environment shader looks. The position of the camera within the scene has no effect on that.
It is possible to place the viewpoint outside the atmosphere in which case an extraplanetary view is obtained. This can be
done by giving an altitude of, for example, 100 km and using the default parameters, pointing the camera downward.
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This is the radius of the planet. A default value of 6 000 km corresponds roughly to the Earth's diameter.
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This controls the overall brightness of the image. With the Automatic Gain Control checkbox unchecked this is an overall scaling
factor.
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When this is checked, the brightness of the environment will be scaled in such a way that the ground directly under the viewpoint
has the
illumination of specified in "view gain." This is very useful for daylight scenes, where one typically puts a nice ground
map on and wants it to be properly illuminated.
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Atmosphere
Atmosphere Parameters
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This is a scale thickness of the atmosphere. The default value of 7400 m corresponds to the thickness the Earth's atmosphere
would have if it were of uniform density.
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This again is a scaling factor for the atmosphere's density. Modifying it has effects on the color of the sky and the sunset.
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A smaller sphere of dust is a part of the atmosphere. This parameter defines its height.
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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.
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The shader works by integrating the air density over a number of invisible sample spheres in the atmosphere. This controls
their number. High values (such as 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 while you are satisfied with the results.
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Ground
Ground Parameters
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The Spherical is useful for extraplanetary scenes, where one 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.
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Lollipop is similar to cloud mapping and is useful for ground scenes where on wants to place a map on the ground.
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Transformations
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The scaling of the map. In lollipop mode, it states how many kilometers each instance of the map should stretch. In spherical
mode, it says how often the map wraps around the planet.
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A rotation of the map
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The translation of the map. The same difference between the modes applies here as with the scale parameter.
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Cloud
Cloud Parameters
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The color of the clouds. Mars has red ones, we like white ones... unless you live in the UK, then you want gray.
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Creates a more turbulent-looking cloud fractal.
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This places the cloud plane in the atmosphere model. 500m is about right.
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Defines the cloud fractal's amplitude.
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The fractal ratio. A value of 0.707 works well.
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Clouds are soft so few iterations are necessary.
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This is the center (expected value) of the fractal. A fractal value of 0 is no cloud while a fractal value of 1 is 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.
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If checked, the clouds become animatable with the time parameter.
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Only enabled once you check the Animate option. Defines the speed of the animation.
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Transformations
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The clouds are placed on the planet using a lollypop mapping. This means that there will be stretching and a seam at the South
pole (negative Y direction). Scaling is in km for convenience, so that a scaling of 1 will give the clouds largest features
1 km diameter.
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This rotates the fractal. This can be useful to eliminate visual artifacts due to repetitiveness in the fractal.
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This offsets the cloud fractal. This can be animated to produce a wind effect.
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Star
Star Parameters
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Defines how much of the sky is occupied with stars.
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A bias on the random brightness distribution.
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Scales the brightness of the stars. Sometimes they are too faint and have to be scaled to become visible.
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The color saturation of the stars. They have random colors which can be made visible by increasing the saturation.
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Controls how much the brightness varies with time.
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The time with which the star's brightness varies.
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Transformations
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A scaling factor for the stars.
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Rotates the stars about the azimuth.
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An offset factor for the stars.
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Moon
Moon Parameters
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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 which only appears bright at night because the sun is so much brighter than the night.
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The size of the moon in degrees. On the Earth, the sun and the moon are roughly the same size.
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Makes a halo around the moon. Good for simulating a frosty night.
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The deviation from vertical of the moon's center.
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The azimuth direction of the moon.
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Sun
Sun Parameters
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The color of the sun. Our sun is very close to white.
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A scaling factor on the sun's color. Because the sun is vastly more luminous than any other celestial body, it is necessary
to be able to easily control its color and have it powerful at the same time. The default of 10 is very conservative, relative
to the real world.
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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 -- this is the physical reality. If you want it to appear dimmer, try setting the attenuation
to 0.5 to 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.
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This is the size of the sun disk in degrees.
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Should the dust produced halo not be sufficient, this parameter makes it possible to make the edges of the sun appear more fuzzy.
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A positioning parameter, defining how many degrees from the vertical the sun's center is located.
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This positions the sun in the XZ plane. 0 is in the X direction and 90 is in the positive Z direction.
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