frudawski

# plotpolarCCT

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.

Usage:

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

Where:

Examples

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])

Result:

Th = 12093
Tv =

14159
11316
10243
13357

Reference

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.