Cloud

Category: Texture

Shader Family: Texture

Output: Color

Simulates a simple cloud with a roughly spherical topology. Based on a 3D fractal function that can be animated. Because of the method used to determine how close to the cloud's silhouette we are, it is necessary to use this shader on objects of spherical shape, like spheres or other curved surfaces.

Texture

Name	The shader's name. Enter any name you like, or leave the default.

Texture Space

Selects the texture projection to use. See Specifying a Texture Projection [Texturing].

Bump Mapping

Enable	Switches bump mapping on or off.
Use Alpha	Will use the texture's alpha channel to achieve a bump map.
Factor	Defines how "bumpy" the bump map will be. A negative value will invert the bump inward and a positive bump map factor will bump outward.
Step	Controls the U, V, and Z steps of a bump map. Use this parameter to "smooth" bumps or make them more jagged.

Cloud

Name	The shader's name. Enter any name you like, or leave the default.
Clouds	Defines the color of fractal clouds.
Sky	Defines the color used for the sky (constant background color).
Include Alpha	Calculates the alpha channel when rendering.
Contrast	Controls the contrast of the colors. 0 uses the average of the two colors, and no blending is attempted. This speeds up rendering a little.

Copy Alpha to RGB

When activated, multiplies the RGB channels with the alpha channel by the factor define in the Alpha Strength parameter.

Alpha Strength

Determines the factor by which the Alpha is multiplied with the RGB channels.

Fractal

Name	The shader's name. Enter any name you like, or leave the default.

Fractal

Noise Type	You can choose two noise functions to build the fractal: Perlin and Recursive.
Level Decay	The amplitude of decay of the fractal iterations, defined as the ratio of the amplitudes of two successive iterations. For values less than 1, successive iterations decrease in amplitude; for values greater than 1, they increase in amplitude and the fractal becomes unbounded.
Frequency Multiplier	The frequency multiplier for subsequent iterations. Fractal frequency is the inverse of scale. Doubling the frequency with the Frequency Multiplier is the same as scaling down the texture by a factor of 0.5. 1 = a sharp fractal texture with low detail; 2 = a more detailed and varying texture.
Complexity	The maximum number of noise iterations used when calculating the fractal. Works with Minimum Level in determining the complexity of the fractal.
Level Minimum	The minimum amplitude at which iteration will continue. Used to determine how often the noise function is called. This parameter can be used to control the amount of detail in the texture.
Time	Defines the time (seconds) used to animate clouds.
Absolute	When on, the fractal procedure uses a slightly different algorithm, which causes discontinuities in the fractal itself. This creates the impression of turbulence.

Edge Transparency

Controls the transparency of clouds' edges and/or centers. Although this creates more realistic clouds, it takes longer to render.

Enable	Switches on the edge transparency parameters.
Range	Controls the abruptness of the change from the center of the cloud to the edge. If the value is small, the change is abrupt.
Amplitude	Defines the base amplitude of the fractal used to calculate the edge transparency. This parameter only applies to the amplitude of the first iteration; successive iterations may further increase the amplitude.
Center Threshold	Defines the average alpha value at the center of the cloud.
Edge Threshold	The corresponding value for the cloud's edge (see the above parameter).

Advanced

Name	The shader's name. Enter any name you like, or leave the default.

Alternate

U, V, Z

Specifies whether every other copy of the repetition should be reversed so that the successive copies of the texture are alternated.

Repeats

Texture Repeats

Contains the repetition factor in X,Y, and Z. A value of 2, for example, shrinks the texture so that it fits twice in a [0..1] interval.

UV Remap

Minimum, Maximum

Determines the remapping of the texture image. For a 2D image, only X and Y are used.

Render Tree Usage

Color parameters can be connected to other textures or image processing shaders. A texture's scalar parameters can be altered to create interesting effects by applying Texture Generator shaders to them. For example, the Contrast can be controlled with the Gradient Texture Generator shader.

A texture shader has limitless capabilities in a render tree. It can texture an object, be used as a camera or light projection, define bump or displacement maps, or be blended with any number of other textures to create any effect.