egs_circle_perpendicular.h

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/*
###############################################################################
#
#  EGSnrc egs++ circle perpendicular shape headers
#  Copyright (C) 2015 National Research Council Canada
#
#  This file is part of EGSnrc.
#
#  EGSnrc 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.
#
#  EGSnrc 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 EGSnrc. If not, see <http://www.gnu.org/licenses/>.
#
###############################################################################
#
#  Author:          Reid Townson, 2020
#
#  Contributors:
#
###############################################################################
*/


#ifndef EGS_CIRCLE_PERPENDICULAR_
#define EGS_CIRCLE_PERPENDICULAR_

#include "egs_shapes.h"
#include "egs_rndm.h"
#include "egs_math.h"

#ifdef WIN32

    #ifdef BUILD_CIRCLE_PERPENDICULAR_DLL
        #define EGS_CIRCLE_PERPENDICULAR_EXPORT __declspec(dllexport)
    #else
        #define EGS_CIRCLE_PERPENDICULAR_EXPORT __declspec(dllimport)
    #endif
    #define EGS_CIRCLE_PERPENDICULAR_LOCAL

#else

    #ifdef HAVE_VISIBILITY
        #define EGS_CIRCLE_PERPENDICULAR_EXPORT __attribute__ ((visibility ("default")))
        #define EGS_CIRCLE_PERPENDICULAR_LOCAL  __attribute__ ((visibility ("hidden")))
    #else
        #define EGS_CIRCLE_PERPENDICULAR_EXPORT
        #define EGS_CIRCLE_PERPENDICULAR_LOCAL
    #endif

#endif

class EGS_CIRCLE_PERPENDICULAR_EXPORT EGS_CirclePerpendicularShape : public EGS_SurfaceShape {

public:

    EGS_CirclePerpendicularShape(EGS_Float Xo, EGS_Float Yo, EGS_Float R, EGS_Float R_i = 0,
                                 const string &Name="",EGS_ObjectFactory *f=0) :
        EGS_SurfaceShape(Name,f), xo(Xo), yo(Yo), ro(R_i), dr(R-R_i) {
        otype = "circle";
        if (dr < 0) {
            ro = R;
            dr = R_i - R;
        }
        A = M_PI*dr*(dr + 2*ro);
    };
    ~EGS_CirclePerpendicularShape() {};
    EGS_Vector getPoint(EGS_RandomGenerator *rndm) {
        EGS_Float r = ro + dr*sqrt(rndm->getUniform());
        EGS_Float cphi, sphi;
        rndm->getAzimuth(cphi,sphi);
        return EGS_Vector(xo + r*cphi, yo + r*sphi, 0);
    };

    void getPointSourceDirection(const EGS_Vector &Xo,
                                 EGS_RandomGenerator *rndm, EGS_Vector &u, EGS_Float &wt) {

        // Perform user requested transformations to a point on the source surface
        // This is effectively the same as transforming the target position
        // because we're just calculating the direction between the two
        EGS_Vector xo = T ? Xo*(*T) : Xo;

        // Get a point on the circle target surface
        EGS_Vector x = getPoint(rndm);
        u = x - xo;
        EGS_Float d2i = 1/u.length2(), di = sqrt(d2i);
        u *= di;

        // Calculate the angle between the normal to the circle surface and the u vector between points
        EGS_Vector perpToCircle = EGS_Vector(0, 0, 1);
        EGS_Float angleBetween = std::acos(u * perpToCircle / (perpToCircle.length() * u.length()));

        // We will rotate about a vector perpendicular to u and the target surface normal
        // Check against fabs(u.z) to account for both parallel and anti-parallel cases
        EGS_Vector rotateAbout;
        if ((fabs(u.z) - perpToCircle.z) < epsilon) {
            rotateAbout = perpToCircle;
        }
        else {
            rotateAbout = u.times(perpToCircle);
        }
        EGS_RotationMatrix rotation = EGS_RotationMatrix::rotV(-angleBetween, rotateAbout);
        EGS_AffineTransform *transform = new EGS_AffineTransform(rotation);
        if (transform) {
            // Transform the point on the target surface by this rotation
            transform->rotate(x);

            // Calculate the new u vector
            u = x - xo;
        }
        delete transform;

        d2i = 1/u.length2(), di = sqrt(d2i);
        u *= di;
        wt = A*u.length()*d2i;
        if (T) {
            T->rotate(u);
        }
    };

protected:

    EGS_Float xo, yo, ro, dr;
};

#endif