spd.h

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/***************************************************************************
 *   Copyright (C) 1998-2010 by authors (see AUTHORS.txt )                 *
 *                                                                         *
 *   This file is part of LuxRays.                                         *
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 *   LuxRays is free software; you can redistribute it and/or modify       *
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 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
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/* SPD classes are from luxrender */

#ifndef _LUXRAYS_SDL_SPD_H
#define _LUXRAYS_SDL_SPD_H

#include <cstddef>

#include "luxrays/luxrays.h"
#include "luxrays/utils/sdl/mc.h"

namespace luxrays { namespace sdl {

class SPD {
public:
        SPD() {
                nSamples = 0U;
                lambdaMin = lambdaMax = delta = invDelta = 0.f;
                samples = NULL;
        }
        virtual ~SPD() { FreeSamples(); }

        // samples the SPD by performing a linear interpolation on the data
        inline float sample(const float lambda) const {
                if (nSamples <= 1 || lambda < lambdaMin || lambda > lambdaMax)
                        return 0.f;

                // interpolate the two closest samples linearly
                const float x = (lambda - lambdaMin) * invDelta;
                const unsigned int b0 = Floor2UInt(x);
                const unsigned int b1 = Min(b0 + 1, nSamples - 1);
                const float dx = x - b0;
                return Lerp(dx, samples[b0], samples[b1]);
        }

        inline void sample(unsigned int n, const float lambda[], float *p) const {
                for (unsigned int i = 0; i < n; ++i) {
                        if (nSamples <= 1 || lambda[i] < lambdaMin ||
                                lambda[i] > lambdaMax) {
                                p[i] = 0.f;
                                continue;
                        }

                        // interpolate the two closest samples linearly
                        const float x = (lambda[i] - lambdaMin) * invDelta;
                        const unsigned int b0 = Floor2UInt(x);
                        const unsigned int b1 = Min(b0 + 1, nSamples - 1);
                        const float dx = x - b0;
                        p[i] = Lerp(dx, samples[b0], samples[b1]);
                }
        }

        float Y() const;
        float Filter() const;
        void AllocateSamples(unsigned int n);
        void FreeSamples();
        void Normalize();
        void Clamp();
        void Scale(float s);
        void Whitepoint(float temp);
        Spectrum ToRGB();

protected:
        unsigned int nSamples;
        float lambdaMin, lambdaMax;
        float delta, invDelta;
        float *samples;

};

// regularly sampled SPD, reconstructed using linear interpolation
class RegularSPD : public SPD {
public:
        RegularSPD() : SPD() {}

        //  creates a regularly sampled SPD
        //  samples    array of sample values
        //  lambdaMin  wavelength (nm) of first sample
        //  lambdaMax  wavelength (nm) of last sample
        //  n          number of samples
        RegularSPD(const float* const s, float lMin, float lMax, unsigned int n) : SPD() {
                init(lMin, lMax, s, n);
        }

        virtual ~RegularSPD() {}

protected:
        void init(float lMin, float lMax, const float* const s, unsigned int n);
};

// only use spline for regular data
enum SPDResamplingMethod { Linear, Spline };

// Irregularly sampled SPD
// Resampled to a fixed resolution (at construction)
// using cubic spline interpolation
class IrregularSPD : public SPD {
public:

        IrregularSPD() : SPD() {}

        // creates an irregularly sampled SPD
        // may "truncate" the edges to fit the new resolution
        //  wavelengths   array containing the wavelength of each sample
        //  samples       array of sample values at the given wavelengths
        //  n             number of samples
        //  resolution    resampling resolution (in nm)
        IrregularSPD(const float* const wavelengths, const float* const samples,
                unsigned int n, float resolution = 5, SPDResamplingMethod resamplignMethod = Linear);

        virtual ~IrregularSPD() {}

protected:
          void init(float lMin, float lMax, const float* const s, unsigned int n);

private:
        // computes data for natural spline interpolation
        // from Numerical Recipes in C
        void calc_spline_data(const float* const wavelengths,
        const float* const amplitudes, unsigned int n, float *spline_data);
};

} }

#endif  /* _LUXRAYS_SDL_SPD_H */

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