The color usage in Octane is actually wavelength based. All RGB inputs that you use in other areas are actually converted to wavelength. Since Octane is a spectral engine, it uses the visible spectrum, where the wavelengths are valid not the rgb. For example, let's say you picked a blue color with a rgb value of 0-51-255 for the diffuse channel. This color is converted by Octane to wavelength and the correspondence is 450 nm (nanometer), hence 0.45 μm (micrometer). That's the value Octane uses. if you ask "What is it to us?", we have a response: This rgb convert operation is not perfect. At higher light intensity, rgb colors are clipped and you may see different (or wrong) color other than the desired color. If you are looking for a realistic render we recommend you use this node because you will be using the realistic spectrum that Octane has used directly without losing color values. Of course, if your goal is motion graphic style renders, you do not have to bother with this node. In this case, you can use RGB (HSV) color space.
how to use
This node allows you to create colors using the Gaussian spectrum distribution curve (or Normal Distribution). The disadvantage is that you do not have a visual reference like any RGB table. When you use it for the first time, you have to struggle with the options to get the color you want. If it helps, it is possible to set up a logic like HSV: consider the Wavelength option as Hue, Width as Saturation and Power as Value. Also, if it's help, you can use the following graph as a kind of reference. We hope that the Octane team adds a meaningful color GUI to this extremely useful option in future versions.
First, open the Node editor and prepare the setup as you see in the picture below. As you can see, its simple to use. You can connect this node to any color inputs of the other channels.
GAUSSIAN SPECTRUM SETTINGS
This represents the mean wavelength approximation between 380nm – 720nm. The lower wavelength values appear bluish while higher wavelengths (around700nm) appears reddish.
Almost no color is visible when using a width of 0.000. On the other hand, a width of 1.000 means the color is spread thin over a large space and the texture will appear faint. We recommend that keep this value low according to the wavelength value.
You can control the brightness from here.