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/*******************************************************************************
* spectral.h
*
* This module contains all defines, typedefs, and prototypes for spectral.cpp.
*
* ---------------------------------------------------------------------------
* Persistence of Vision Ray Tracer ('POV-Ray') version 3.7.
* Copyright 1991-2013 Persistence of Vision Raytracer Pty. Ltd.
*
* POV-Ray is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* POV-Ray is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
* ---------------------------------------------------------------------------
* POV-Ray is based on the popular DKB raytracer version 2.12.
* DKBTrace was originally written by David K. Buck.
* DKBTrace Ver 2.0-2.12 were written by David K. Buck & Aaron A. Collins.
* ---------------------------------------------------------------------------
* $File: //depot/public/povray/3.x/source/backend/colour/spectral.h $
* $Revision: #1 $
* $Change: 6069 $
* $DateTime: 2013/11/06 11:59:40 $
* $Author: chrisc $
*******************************************************************************/
#ifndef SPECTRAL_H
#define SPECTRAL_H
namespace pov
{
using namespace pov_base;
#define SPECTRAL_VIOLET 380.0 // extreme violet
#define SPECTRAL_RED 730.0 // extreme red
#define SPECTRAL_BANDWIDTH (SPECTRAL_RED-SPECTRAL_VIOLET)
#define SPECTRAL_CENTER ((SPECTRAL_VIOLET + SPECTRAL_RED)/2) // TODO - maybe should define this as yellow
/// Class representing a spectral band.
class SpectralBand
{
public:
/// Default Constructor.
SpectralBand():
wavelength ( (SPECTRAL_VIOLET + SPECTRAL_RED)/2 ), // deliberately NOT using SPECTRAL_CENTER
bandwidth ( SPECTRAL_BANDWIDTH )
{}
/// Construct by abstract band index (ranging from 0 to N-1).
SpectralBand(unsigned int band, unsigned int bands):
wavelength ( SPECTRAL_VIOLET + SPECTRAL_BANDWIDTH*( ((float)band+0.5)/(float)bands ) ),
bandwidth ( SPECTRAL_BANDWIDTH/(float)bands )
{}
/// Construct by spectral band and sub-band index (ranging from 1 to N).
SpectralBand(const SpectralBand& super, unsigned int subBand, unsigned int subBands):
wavelength ( super.wavelength + super.bandwidth*( ((float)subBand+0.5)/(float)subBands - 0.5 ) ),
bandwidth ( super.bandwidth/(float)subBands )
{}
/// Construct by physical parameters.
SpectralBand(float wl, float bw):
wavelength(wl),
bandwidth(bw)
{}
/// Get peak wavelength.
float GetWavelength() const
{
return wavelength;
}
/// Get corrected IOR
double GetDispersionIOR(double nominalIOR, double nominalDispersion) const
{
return nominalIOR * pow(nominalDispersion, -(wavelength-SPECTRAL_CENTER)/SPECTRAL_BANDWIDTH );
}
/// Get hue
RGBColour GetHue() const
{
return (GetHueIntegral(wavelength+bandwidth/2) - GetHueIntegral(wavelength-bandwidth/2)) * (SPECTRAL_BANDWIDTH/bandwidth);
}
private:
/// Peak wavelength.
float wavelength;
/// Nominal bandwidth.
float bandwidth;
static RGBColour GetHueIntegral(double wavelength);
};
}
#endif // SPECTRAL_H
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