The plotpolarCCT function calculates and plots the resulting horizontal and vertical Correlated Colour Temperatures (CCTs) T_{cp,i} from the Tregenza luminance distribution with 145 patches and the colour coordinates x and y. The illustration is also known under the name spectral daylight potential diagram (SDPD), see Diakite-Kortlever and Knoop.

See also: polardataCCT, plotpolarE


[Th,Tv] = plotpolarCCT(x,y,L,vdir)


ThIs the resulting horizontal CCT T_{cp,h}.
TvAre the resulting vertical CCTs T_{cp,v,i} in i vertical directions, specified by the vdir parameter. Note: this method neglects the influence of the sourrounding reflectances e.g. the environment terrain.
x and yAre the Tregenza patches CIE 1931 colour coordinates x and y as 145 \times 1 vector.
LIs the Tregenza luminance distribution in \textrm{cd}\cdot\textrm{m}^2 as 145 \times 1 vector.
Specifies the vertical compass direction using the azimuth angle, starting in north and going clockwise, default [0:359]. For compass directions north, east, south, west use: [0 90 180 270]


Horizontal and vertical illuminance (N,E,S,W) for CIE sky 12 with \alpha_S=160° and \gamma_S = 40°:

[~,~,L,~,x,y] = specsky(12,160,40);
[Th,Tv] = plotpolarCCT(x,y,L,[0 90 180 270])

See also: specsky


Th = 12093
Tv =



Peter Roy Tregenza: Subdivision of the sky hemisphere for luminance measurements. In: Lighting Research and Technology, vol. 19, no. 1, pp. 13-14, 1987, (DOI: 10.1177/096032718701900103).

Aicha K. Diakite-Kortlever, Martine Knoop: Non-image forming potential in urban settings – An approach considering orientation-dependent spectral properties of daylight. In: Energy and Buildings, vol. 265, pp. 112080, 2022, ISSN: 0378-7788.

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