//******************************************************************************
//** SCATMECH: Polarized Light Scattering C++ Class Library
//** 
//** File: finiteaperture.cpp
//**
//** Thomas A. Germer
//** Optical Technology Division, National Institute of Standards and Technology
//** 100 Bureau Dr. Stop 8443; Gaithersburg, MD 20899-8443
//** Phone: (301) 975-2876; FAX: (301) 975-6991
//** Email: thomas.germer@nist.gov
//**
//** Version: 6.00 (February 2008)
//**
//******************************************************************************
#include "scatmech.h"
#include "finiteaperture.h"
#include "focussedbeam.h"
#include "askuser.h"


namespace SCATMECH {


    //
    // Constructor...
    //
    Finite_Aperture_Instrument_BRDF_Model::
    Finite_Aperture_Instrument_BRDF_Model()
    {
        model_cs = xyxy;    // Added 15 June 2004 by TAG
    }

    MuellerMatrix 
    Finite_Aperture_Instrument_BRDF_Model::
    mueller()
    {
        synchronize(model);
        SETUP();

        if (alpha==0.) return model->Mueller(thetai,thetas,phis,rotation,xyxy);    // Modified 15 June 2004 by TAG

        MuellerMatrix m=MuellerZero();

        for (int i=0;i<Circle_Integral::n();++i) {
            double theta = Circle_Integral::theta(i);
            double r = Circle_Integral::r(i);
            double w = Circle_Integral::w(i);

            r = r*alpha*deg;

            Vector v = four_angles(thetas,phis,r,theta);

            double thetas_ = acos(v.z);
            double phis_ = atan2(v.y,v.x);

            m += model->Mueller(thetai,thetas_,phis_,rotation,xyxy)*w*cos(thetas_); // Modified 15 June 2004 by TAG
        }
        return (m/cos(thetas));
    }

    //
    // The following returns a unit vector, defined by the angles theta, phi, alpha, and beta:
    // Adds planar vector (alpha, beta) on unit sphere to vector (theta,phi).
    //
    Vector 
    Finite_Aperture_Instrument_BRDF_Model::
    four_angles(double theta,double phi,double alpha,double beta) 
    {
        return Vector(
                cos(beta)*sin(alpha)*sin(phi) + 
                    cos(phi)*(cos(theta)*sin(alpha)*sin(beta) + cos(alpha)*sin(theta)),
                -(cos(beta)*cos(phi)*sin(alpha)) + 
                    sin(phi)*(cos(theta)*sin(alpha)*sin(beta) + cos(alpha)*sin(theta)),
                cos(alpha)*cos(theta) - sin(alpha)*sin(beta)*sin(theta));
    }

    DEFINE_MODEL(Finite_Aperture_Instrument_BRDF_Model,Instrument_BRDF_Model, 
                "Finite_Aperture_Instrument_BRDF_Model",
                "A BRDF model evaluated with a finite collection aperture.");

    DEFINE_PTRPARAMETER(Finite_Aperture_Instrument_BRDF_Model,BRDF_Model_Ptr,model,"BRDF Model to be integrated","Microroughness_BRDF_Model");

    DEFINE_PARAMETER(Finite_Aperture_Instrument_BRDF_Model,double,alpha,"Opening half angle of detector [deg]","0");


}