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function [spd,xd,yd,M1,M2] = GenerateCIEDay(Temp,B)
% [spd,xd,yd] = GenerateCIEDay(Temp,[B])
%
% Generate CIE daylights of the desired correlated color
% temperature. Formulae are from W+S, pp. 145-146.
%
% The required basis vectors may be obtained by loading
% the file B_cieday.
%
% INPUT
% Temp - row vector of color temperatures. These should be
% in the range 4000 - 25000.
% B - CIE daylight basis vectors.
%
% OUTPUT
% spd - desired spectral power distributions
% xd - row vector of x chromaticities
% yd - row vector of y chromaticities
%
% 9/28/93 dhb, jms Changed argument name to Temp
% If B not passed, return spd = [] and other data
% Get sizes
[null,m] = size(Temp);
xd = zeros(1,m);
yd = zeros(1,m);
% Compute xd chromaticities
index = find(Temp < 7000);
if (length(index) > 0)
xd(index) = -4.6070*1e9./(Temp(index).^3) + 2.9678*1e6./(Temp(index).^2) ...
+ 0.09911*1e3./(Temp(index)) + 0.244063;
end
index = find(Temp >= 7000);
if (length(index) > 0)
xd(index) = -2.0064*1e9./(Temp(index).^3) + 1.9018*1e6./(Temp(index).^2) ...
+ 0.24748*1e3./(Temp(index)) + 0.237040;
end
% Compute yd chromaticities
yd = -3.*(xd.^2) + 2.870.*xd - 0.275;
% Compute M0, M1 and M2
M0 = ones(1,m);
M1 = (-1.3515 - 1.7703.*xd + 5.9114.*yd) ./ ...
(0.0241 + 0.2562.*xd - 0.7341 .* yd);
M2 = (0.03 - 31.4424.*xd + 30.0717.*yd) ./ ...
(0.0241 + 0.2562.*xd - 0.7341 .* yd);
% Compute the SPD
M = [M0 ; M1 ; M2];
if (nargin == 2)
spd = B*M;
else
spd = [];
end
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