The polardataCCT function calculates the resulting horizontal and vertical Correlated Colour Temperatures (CCTs) T_{cp,i} from the Tregenza radiance distribution with 145 patches and the colour coordinates x and y.
Usage:
[Th,Tv] = polardataCCT(x,y,L,vdir,omega,method)
Where:
| Parameter | Description |
Th | Is the resulting horizontal integral CCT T_{cp,h}. |
Tv | Are the resulting vertical integral CCT 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,y | Are the Tregenza patches CIE 1931 colour coordinates x and y as 145 \times 1 vector. |
L | Is the Tregenza luminance distribution in \textrm{cd}\cdot\textrm{m}^2 as 145 \times 1 vector. |
vdir | 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] |
omega | Defines the patches solid angles in \mathrm{sr} as 145 \times 1 vector. Default value: 9.6° \approx 0.022~\mathrm{sr}. |
method | Defines the CCT determination method: ‘Robertson’ (default) ‘exact’ See also: ciexy2cct |
Examples
Horizontal and vertical resulting CCT (N,E,S,W) for CIE sky 12 with \alpha_S=166° and \gamma_S = 33°:
x = linspace(0.2,0.4,145); y = linspace(0.4,0.3,145); Y = ciesky(12,166,33); [Th,Tv] = polardataCCT(x,y,Y,[0 90 180 270])
See also: ciesky
Result:
Th = 6109 Tv = 8412 8052 8028 8285
Horizontal and vertical resulting CCT for \alpha = 0°, 30°, 60°, 90°, 120°, 150°, 180° for CIE sky 5 with \alpha_S=180° and \gamma_S = 30°, \omega = 12° = 0.03442~\textrm{sr} and method = ‘exact’:
x = linspace(0.2,0.4,145); y = linspace(0.4,0.3,145); Y = ciesky(5,180,30); omega = ones(1,145).*0.03442; [Th,Tv] = polardataCCT(x,y,Y,[0 30 60 90 120 150 180],omega,'exact')
See also: ciesky
Result:
Th = 5328 Tv = 7476.9 7477.8 7460.7 7459.8 7450.7 7466.0 7471.2
Reference