The Noise Gradient component produces a horizontal or vertical gradient composed of randomly colored stripes of variable width and position. The range of colors is determined by the H Range, L Range and S Range parameters, with the Base Color as the middle point of each range. Technically, the gradient is formed by three one-dimensional Perlin noise functions, one for each of the H, L and S channels. The channels are assembled together according to the HLS color model. Noise Gradient is a map component, it can be located in the Gradients category on the Components Bar.
Base Color: Map Input
Determines the base color of the gradient. To set the base color of various image areas separately, connect a map component to this input.
H Range: Map Input
Narrows or widens the range of hues used in the gradient. The middle point of the hue range is determined by the hue of the Base Color according to the HLS color model. With H Range of 0, all stripes in the gradient will have the same hue (that of the Base Color); and with H Range of 100, all hues of the spectrum are used. The hue of each gradient stripe is chosen randomly within this range. Since H Range is a map input, its value can be controlled separately for different image areas by connecting a map component to this input.
L Range: Map Input
Narrows or widens the lightness range of the gradient. The middle point of the lightness range is determined by the lightness of the Base Color according to the HLS color model. With L Range of 0, all stripes in the gradient will have the same lightness (that of the Base Color); and with L Range of 100, the full lightness range is used. The lightness value for each gradient stripe is chosen randomly within this range. Since L Range is a map input, its value can be controlled separately for different image areas by connecting a map component to this input.
If the resulting range includes lightness values above 100 or below 0, the range is clipped accordingly. For example, if the middle point (Base Color) has the lightness of 0, and the L Range is set to 100, the resulting range will be -50 to 50, which will be clipped to the range of 0 to 50.
S Range: Map Input
Narrows or widens the saturation range of the gradient. The middle point of the saturation range is determined by the saturation of the Base Color according to the HLS color model. With S Range of 0, all stripes in the gradient will have the same saturation (that of the Base Color); and with S Range of 100, the full saturation range is used. The saturation value for each gradient stripe is chosen randomly within this range. Since S Range is a map input, its value can be controlled separately for different image areas by connecting a map component to this input.
If the resulting range includes saturation values above 100 or below 0, the range is clipped accordingly. For example, if the middle point (Base Color) has the saturation of 0, and the S Range is set to 100, the resulting range will be -50 to 50, which will be clipped to the range of 0 to 50.
Roughness: Map Input
Defines the roughness of the noise the gradient is based upon. Technically, Roughness defines the relative strength of the octaves that compose each of the H, L, and S noise functions (the number of octaves in each function is controlled by the Details parameter). Roughness of 0 sets all octaves but the first to zero strength, which is equivalent to setting the Details parameter to 0. Low roughness, approximately 0 to 30, results in smoother noise because large-grained octaves have the greatest visibility. Higher roughness values increase the visibility of smaller-grained octaves, making the noise rougher. Roughness has no effect when Details is set to 0, because in this case only one octave is visible. Since Roughness is a map input, its value can be controlled separately for different image areas by connecting a map component to this input.
Lower Roughness can speed up the rendering – when the visibility of smaller-grained octaves is very close to zero, they are 'turned off' to save the rendering time. Also, avoid using Roughness values of 50 and higher for height maps, because this can lead to clamping artifacts which appear as flat regions on the height map.
Vertical: Map Input
When turned on, the gradient goes in vertical direction, otherwise in horizontal. When a map component is connected to this input, the state of the checkbox is determined separately for different image areas by the brightness level of the image supplied by that component. The brightness level of 0 to 50 corresponds to unchecked Vertical, and the level of 50 to 100 corresponds to checked Vertical.
Contrast: Map Input
Adjusts the contrast of the noise gradient. The contrast adjustment uses the same algorithm as the Brightness / Contrast component with the Preserve Color option turned on. Since Contrast is a map input, its value can be controlled separately for different image areas by connecting a map component to this input.
Adjusts the gradient scale. The resulting scale is also affected by the global parameter Size.
Defines the complexity of the noise the gradient is based upon. Technically, Details sets the number of the octaves for each of the H, L, and S noise functions. Details of 0 means one octave per channel, 20 means 3 octaves and 100 means 11 octaves per channel. Values such as 27 mean that first three octaves have full visibility, and the fourth one has 70% visibility. Details has no effect when Roughness is set to 0, because in this case only the first octave has 100% visibility no matter how many octaves are active.
Large Details value leads to longer rendering times because it increases the number of octaves to calculate. For example, when Details is set to 0, only one octave per channel is rendered. When Details is 100, eleven octaves are rendered which can slow down the rendering up to eleven times. So if you don't need a high number of octaves, you can lower it to make the filter quicker.
Variation, technically known as random seed, affects the random aspects of the component which cannot be controlled directly: it randomizes the location, width, hue, saturation and lightness of the gradient stripes. If the Randomizable parameter is turned on, the randomization is also affected by the global Variation value. For more information, see How Variation Works.
When turned on, the global Variation parameter will affect the image generated by the component. When this parameter is turned off, the global Variation has no effect on the component. This may come in useful when you need to 'lock' the appearance of the gradient and don't want the global Variation to change it.
