Octane Gaussian Spectrum Texture

Last modified: 10 March 2025

The color usage in OctaneRender® is spectrum-based, using the wavelength of visible light. All RGB inputs that you use in other areas are converted to a specific wavelength of a given RGB color. RGB values themselves are just an approximation of an actual, true color — color is light, after all — therefore, the most precise definition of a given color is its own actual light wavelength. RGB is not a precise method to calculate color and can actually fail when used for bright emission. For this reason, the Gaussian spectrum node is recommended instead.

The Gauss Spectrum texture is based on a Gaussian distribution spectrum. WaveLength sets the center of the spectrum, and Width sets the curve's width. Power sets the brightness of the color.

The narrower the width, the more pure and saturated the color.

The image below shows Gauss Spectrum node connected to a Material's Diffuse input.

Layout_UxCQbr8vK2.png

Gaussian Spectrum Attributes

This node allows enables the creation of colors using the Gaussian spectrum distribution curve (or Normal Distribution).

The image below illustrates the visible spectrum with wavelength values:

Gauissian_Spectrum.png

note

Ultraviolet (blue) is on the left side of the spectrum and infrared (red) is on the right side. The opposite is true for the Kelvin (color temperature) scale.

Octane remaps the Wavelength, Width and Power values of the Gaussian spectrum into a range from 0.0 to 1.0. As a result, entering an actual wavelength value directly from the Gaussian spectrum will not give the expected results. To make it easier to get the desired color, consisting of a Cube Object with an Octane Diffuse material applied; a Gaussian Spectrum node is piped into the Diffuse input of the material. Launch Live Viewer and make adjustments to the Wavelength, Width and Power values to dial in the color you need, then copy that node into your material or light in the Node Editor.

You can pop out the Attribute panel and lock it the Gaussian spectrum node to make your adjustments if you wish.

The following attributes control the behaviour of the Gaussian Spectrum Node.

  • Wavelength - The mean wavelength approximation between 380 nm - 720 nm (with a range from 0 - 1). Lower values appear bluish, and higher values (around 700 nm) appear reddish. Wavelength is roughly the same as Hue in the HSV color model, though not completely. This represents the mean wavelength approximation between 380nm – 720nm, which Octane remaps into 0.0 to 1.0. The lower wavelength values will be in the blue range while higher values be in the red range.

  • Width - When set to 0, almost no color is visible. When set to 1, the color spreads thin over a large space, and the texture appears faint.

  • Power - The texture's brightness.

As Octane is dealing with Wavelengths, Width and Power, simple discreet color choices (such as RGB blue 0,0,1) or HSV blue (0.66667, 1, 1) can be a little less intuitive (for those who have been using computers to pick colors for any real length of time).

These models and others are mere approximations of the actual colors that we see, which the Gaussian spectrum accurately describes.