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A spectrum element describes a wavelength-dependent parameter. They are used for describing light sources, material properties, instrument sensivities, ... Spectra may have different units depending on their context of use : transmission spectra are unit-less, while source spectral radiance is given in W·m−2·sr−1·m−1. There are several spectrum types. For instance, tabulated spectrum uses only tabulated user data. Other spectrum types follow physical laws (such as blackbody which uses Planck's law) and are defined by a few parameters.


This is the most simple spectrum type with a uniform, wavelength-independent value.

Uniform spectrum reference


The preset spectrum type accesses the spectra stored in the program, given a spectrum name.

Preset spectrum reference


This spectrum type takes tabulated spectral values as input

Tabulated spectrum reference


This spectrum type is designed mainly for emitters. It is equal to the blackbody radiation spectrum defined by Planck's law.

Blackbody spectrum reference


This spectrum type corresponds to a square shaped spectrum, with a constant "top" value between two wavelengths, and a "base" value otherwise.

Peak spectrum reference


This spectrum type corresponds to Cauchy's equation for dielectrics.

Cauchy spectrum reference


This spectrum type allows adjusting spectral properties with RGB values as in traditional computer graphic software.

RGB spectrum reference

See also

Node types