// -*- C++ -*-
/* Copyright 1999 
 * Thu Apr 15 17:00:04 1999  Brian Smits  (bes@phoenix.cs.utah.edu)
 * 
 * RiToSpectrum.C
 * 
 *	
 * 
 * $Id: RiToSpectrum.C,v 1.1 1999/06/10 20:12:34 bes Exp $ 
 * 
 */
#ifndef RICOMMON_H
#include <RiCommon.H>
#endif


#ifndef RISUNSKY_H
#include <RiSunSky.H>
#endif

#ifndef RISPECTRALCURVE_H
#include <RiSpectralCurve.H>
#endif


//300-830 10nm
static float S0Amplitudes[54] = {
0.04,6.0,29.6,55.3,57.3,
61.8,61.5,68.8,63.4,65.8,
94.8,104.8,105.9,96.8,113.9,
125.6,125.5,121.3,121.3,113.5,
113.1,110.8,106.5,108.8,105.3,
104.4,100.0,96.0,95.1,89.1,
90.5,90.3,88.4,84.0,85.1,
81.9,82.6,84.9,81.3,71.9,
74.3,76.4,63.3,71.7,77.0,
65.2,47.7,68.6,65.0,66.0,
61.0,53.3,58.9,61.9
};

static float S1Amplitudes[54] = {
0.02,4.5,22.4,42.0,40.6,
41.6,38.0,42.4,38.5,35.0,
43.4,46.3,43.9,37.1,36.7,
35.9,32.6,27.9,24.3,20.1,
16.2,13.2,8.6,6.1,4.2,
1.9,0.0,-1.6,-3.5,-3.5,
-5.8,-7.2,-8.6,-9.5,-10.9,
-10.7,-12.0,-14.0,-13.6,-12.0,
-13.3,-12.9,-10.6,-11.6,-12.2,
-10.2,-7.8,-11.2,-10.4,-10.6,
-9.7,-8.3,-9.3,-9.8
};

static float S2Amplitudes[54] = {
0.0,2.0,4.0,8.5,7.8,
6.7,5.3,6.1,3.0,1.2,
-1.1,-0.5,-0.7,-1.2,-2.6,
-2.9,-2.8,-2.6,-2.6,-1.8,
-1.5,-1.3,-1.2,-1.0,-0.5,
-0.3,0.0,0.2,0.5,2.1,
3.2,4.1,4.7,5.1,6.7,
7.3,8.6,9.8,10.2,8.3,
9.6,8.5,7.0,7.6,8.0,
6.7,5.2,7.4,6.8,7.0,
6.4,5.5,6.1,6.5
};


static RiSpectrum riS0Spectrum, riS1Spectrum, riS2Spectrum;

void InitChromaticityToSpectrum()
{
    riS0Spectrum = RiRegularSpectralCurve(S0Amplitudes,300,830,54);
    riS1Spectrum = RiRegularSpectralCurve(S1Amplitudes,300,830,54);
    riS2Spectrum = RiRegularSpectralCurve(S2Amplitudes,300,830,54);
}

RiSpectrum RiSunSky::ChromaticityToSpectrum(RiReal x, RiReal y) const
{
    static bool inited = false;
    if(!inited) {
	inited = true;
	InitChromaticityToSpectrum();
    }
    
    RiReal M1 = (-1.3515 - 1.7703*x +  5.9114*y)/(0.0241 + 0.2562*x - 0.7341*y);
    RiReal M2 = ( 0.03   -31.4424*x + 30.0717*y)/(0.0241 + 0.2562*x - 0.7341*y);

    return riS0Spectrum + M1 * riS1Spectrum + M2 * riS2Spectrum;   
}