frudawski

# polardataE

The polardataE function calculates the resulting horizontal and vertical illuminances for a given Tregenza luminance distribution with 145 patches. The Tregenza hemisphere is assumed to have 100% coverage as in figure 1 in contrast to the original Tregenza model.

Usage:

[Eh,Ev] = polardataE(L,vdir)

Where:

Examples

Horizontal and vertical illuminance (N,E,S,W) for CIE sky 5 with \alpha_S=180° and \gamma_S = 40°:

L = ciesky(5,180,40,'Eh',10000);
[Eh,Ev] = polardataE(L,[0 90 180 270])

Result:

Eh = 10000.0
Ev =

4896.3
4904.7
4900.4
4896.6

Note: CIE sky 5 has a uniform luminance distribution. The differences in the resulting vertical illuminances are due to different patch center coordinates which are used for cosine correction of the individual patch.

Vertical illuminance for \alpha = 160° for CIE sky 12 with \alpha_S=160° and \gamma_S = 40°:

L = ciesky(12,160,40,'Eh',50000);
[~,Ev] = polardataE(L,160)

Ev = 5.0554e+04
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).