/*

Copyright 2018 Lingqi Yan

This file is part of WaveOpticsBrdf.

WaveOpticsBrdf is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

WaveOpticsBrdf 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with WaveOpticsBrdf.  If not, see <https://www.gnu.org/licenses/>.

*/

#include "gaborkernel.h"

comp GaborKernel::eval(Vector2 s) {
    return C * G(s, mu, sigma) * cnis(Float(2.0 * M_PI * a.dot(s)));
}

comp GaborKernel::xform(Vector2 u) {
    Float sigmaPrime = Float(1.0 / (2.0 * M_PI * sigma));
    comp CPrime = C * Float(1.0 / (2.0 * M_PI * sigma * sigma)) * cnis(Float(2.0 * M_PI * a.dot(mu)));
    GaborKernel g(-a, sigmaPrime, mu, CPrime);
    return g.eval(u);
}

GaborKernel GaborKernelPrime::toGaborKernel(Float lambda) {
    Float l = sigma * SCALE_FACTOR;
    comp C = l * l * cnis(4.0 * M_PI / lambda * cInfo);
    Vector2 a = aInfo / lambda;

    return GaborKernel(mu, sigma, a, C);
}

Vector2 GaborKernelPrime::getFFTCenter(Float lambda) {
    return -aInfo / lambda;
}

Float GaborKernelPrime::getFFTWidth() {
    return 1.0 / (2.0 * M_PI * sigma);
}