Light Utilities

All light shaders take an argument determining the color of the light source. Here we describe some light utilities that may be used to determine a color. They can be attached to the color parameters of other light shaders.

CIE D Illuminant

The Comission Internationale de l'Eclairage (CIE) has standardized several illuminants. The most well known of these is called D65, but there is an entire range of CIE D illuminants. The number 65 refers to the associated color temperature of 6500 Kelvin. This illuminant describes the color of daylight with an overcast sky. This specific illuminant is widely used to define the color white, and indeed its sRGB coordinates are (1,1,1). The other CIE D illuminant differ from D65 by the associated color temperature. This implementiation supports color temperatures from 4000 Kelvin to 25000 Kelvin.

mib_cie_d
color "mib_cie_d" (
    scalar          "temperature",
    scalar          "intensity")
temperature
gives the associated color temperature of the CIE D illuminant in degrees Kelvin. The allowed range is from 4000 to 25000 Kelvin with a default value of 6500 Kelvin.

intensity
determines the intensity of returned color. By default the intensisty is set to 1.

Blackbody Radiator

An ideal material absorbing all light directed at it is called a blackbody, since it is obviously devoid of any color. However, every material, when sufficiently heated, will also emit electromagnetic radiation. For a blackbody the spectral distribution of this radiation depends solely on the temperature of the material, and on no other material property. There is a specific color associated with each temperature of such a body. With increasing temperature this color ranges from red over white to blue. However, the intensity of this radiation will also increase strongly with temperature - an effect that is ignored here by normalizing the color to a provided intensity.

mib_blackbody
color "mib_blackbody" (
    scalar          "temperature",
    scalar          "intensity")
temperature
gives the temperature in degree Kelvin to be used for the calculation of the blackbody radiation spectrum. The smallest temperatures provided should be near 1000 Kelvin.

intensity
the shader only computes the color corresponding to the provided temperature, but it does not compute the associated intensity. Instead this intensity parameter, with a default value of 1, is used.

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