frudawski

plotpolarE

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

See also: polardataE, plotpolarCCT

Figure 1: Tregenza hemisphere with 100% coverage

Usage:

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

Where:

ParameterDescription
EhIs the resulting horizontal illuminance E_h.
EvAre the resulting vertical illuminances E_{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.
LIs the Tregenza luminance distribution in \textrm{cd}\cdot\textrm{m}^2 as 145 \times 1 vector.
vdir
(optional)
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]

Examples

Horizontal and vertical illuminance (N,E,S,W) for CIE sky 12 with \alpha_S=180° and \gamma_S = 40°:

L = ciesky(12,180,40,'Eh',1e4);
[Eh,Ev] = plotpolarE(L,[0 90 180 270])

See also: ciesky

Result:

Eh = 10000.0
Ev =

   3.5917e+03
   6.1367e+03
   1.0112e+04
   4.4096e+03

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).

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