/*******************************************************************************
*
* McXtrace, X-ray tracing package
*         Copyright, All rights reserved
*         DTU Physics, Kgs. Lyngby, Denmark
*         Synchrotron SOLEIL, Saint-Aubin, France
*
* Component: SasView_stacked_disks
*
* %Identification
* Written by: Jose Robledo
* Based on sasmodels from SasView
* Origin: FZJ / DTU / ESS DMSC
*
*
* SasView stacked_disks model component as sample description.
*
* %Description
*
* SasView_stacked_disks component, generated from stacked_disks.c in sasmodels.
*
* Example: 
*  SasView_stacked_disks_aniso(thick_core, thick_layer, radius, n_stacking, sigma_d, sld_core, sld_layer, sld_solvent, theta, Phi, 
*     model_scale=1.0, model_abs=0.0, xwidth=0.01, yheight=0.01, zdepth=0.005, R=0, 
*     int target_index=1, target_x=0, target_y=0, target_z=1,
*     focus_xw=0.5, focus_yh=0.5, focus_aw=0, focus_ah=0, focus_r=0, 
*     pd_thick_core=0.0, pd_thick_layer=0.0, pd_radius=0.0, pd_theta=0.0, pd_Phi=0.0)
*
* %Parameters
* INPUT PARAMETERS:
* thick_core: [Ang] ([0, inf]) Thickness of the core disk.
* thick_layer: [Ang] ([0, inf]) Thickness of layer each side of core.
* radius: [Ang] ([0, inf]) Radius of the stacked disk.
* n_stacking: [] ([1, inf]) Number of stacked layer/core/layer disks.
* sigma_d: [Ang] ([0, inf]) Sigma of nearest neighbor spacing.
* sld_core: [1e-6/Ang^2] ([-inf, inf]) Core scattering length density.
* sld_layer: [1e-6/Ang^2] ([-inf, inf]) Layer scattering length density.
* sld_solvent: [1e-6/Ang^2] ([-inf, inf]) Solvent scattering length density.
* Optional parameters:
* model_abs: [ ] Absorption cross section density at 2200 m/s.
* model_scale: [ ] Global scale factor for scattering kernel. For systems without inter-particle interference, the form factors can be related to the scattering intensity by the particle volume fraction.
* xwidth: [m] ([-inf, inf]) Horiz. dimension of sample, as a width.
* yheight: [m] ([-inf, inf]) vert . dimension of sample, as a height for cylinder/box
* zdepth: [m] ([-inf, inf]) depth of sample
* R: [m] Outer radius of sample in (x,z) plane for cylinder/sphere.
* target_x: [m] relative focus target position.
* target_y: [m] relative focus target position.
* target_z: [m] relative focus target position.
* target_index: [ ] Relative index of component to focus at, e.g. next is +1.
* focus_xw: [m] horiz. dimension of a rectangular area.
* focus_yh: [m], vert. dimension of a rectangular area.
* focus_aw: [deg], horiz. angular dimension of a rectangular area.
* focus_ah: [deg], vert. angular dimension of a rectangular area.
* focus_r: [m] case of circular focusing, focusing radius.
* pd_thick_core: [] (0,inf) defined as (dx/x), where x is de mean value and dx the standard devition of the variable.
* pd_thick_layer: [] (0,inf) defined as (dx/x), where x is de mean value and dx the standard devition of the variable.
* pd_radius: [] (0,inf) defined as (dx/x), where x is de mean value and dx the standard devition of the variable.
* pd_theta: [] (0,360) defined as (dx/x), where x is de mean value and dx the standard devition of the variable.
* pd_Phi: [] (0,360) defined as (dx/x), where x is de mean value and dx the standard devition of the variable
*
* %Link
* %End
*******************************************************************************/
DEFINE COMPONENT SasView_stacked_disks_aniso

SETTING PARAMETERS (
        thick_core=10.0,
        thick_layer=10.0,
        radius=15.0,
        n_stacking=1.0,
        sigma_d=0,
        sld_core=4,
        sld_layer=0.0,
        sld_solvent=5.0,
        theta=0,
        Phi=0,
        model_scale=1.0,
        model_abs=0.0,
        xwidth=0.01,
        yheight=0.01,
        zdepth=0.005,
        R=0,
        target_x=0,
        target_y=0,
        target_z=1,
        int target_index=1,
        focus_xw=0.5,
        focus_yh=0.5,
        focus_aw=0,
        focus_ah=0,
        focus_r=0,
        pd_thick_core=0.0,
        pd_thick_layer=0.0,
        pd_radius=0.0,
        pd_theta=0.0,
        pd_Phi=0.0)


SHARE %{
%include "sas_kernel_header.c"

/* BEGIN Required header for SASmodel stacked_disks */
#define HAS_Iqac
#define HAS_Iq
#define FORM_VOL

#ifndef SAS_HAVE_polevl
#define SAS_HAVE_polevl

#line 1 "polevl"
/*							polevl.c
 *							p1evl.c
 *
 *	Evaluate polynomial
 *
 *
 *
 * SYNOPSIS:
 *
 * int N;
 * double x, y, coef[N+1], polevl[];
 *
 * y = polevl( x, coef, N );
 *
 *
 *
 * DESCRIPTION:
 *
 * Evaluates polynomial of degree N:
 *
 *                     2          N
 * y  =  C  + C x + C x  +...+ C x
 *        0    1     2          N
 *
 * Coefficients are stored in reverse order:
 *
 * coef[0] = C  , ..., coef[N] = C  .
 *            N                   0
 *
 * The function p1evl() assumes that C_N = 1.0 and is
 * omitted from the array.  Its calling arguments are
 * otherwise the same as polevl().
 *
 *
 * SPEED:
 *
 * In the interest of speed, there are no checks for out
 * of bounds arithmetic.  This routine is used by most of
 * the functions in the library.  Depending on available
 * equipment features, the user may wish to rewrite the
 * program in microcode or assembly language.
 *
 */


/*
Cephes Math Library Release 2.1:  December, 1988
Copyright 1984, 1987, 1988 by Stephen L. Moshier
Direct inquiries to 30 Frost Street, Cambridge, MA 02140
*/
#pragma acc routine seq
static
double polevl( double x, pconstant double *coef, int N )
{

    int i = 0;
    double ans = coef[i];

    while (i < N) {
        i++;
        ans = ans * x + coef[i];
    }

    return ans;
}

/*							p1evl()	*/
/*                                          N
 * Evaluate polynomial when coefficient of x  is 1.0.
 * Otherwise same as polevl.
 */
#pragma acc routine seq
static
double p1evl( double x, pconstant double *coef, int N )
{
    int i=0;
    double ans = x+coef[i];

    while (i < N-1) {
        i++;
        ans = ans*x + coef[i];
    }

    return ans;
}


#endif // SAS_HAVE_polevl


#ifndef SAS_HAVE_sas_J1
#define SAS_HAVE_sas_J1

#line 1 "sas_J1"
/*							j1.c
 *
 *	Bessel function of order one
 *
 *
 *
 * SYNOPSIS:
 *
 * double x, y, j1();
 *
 * y = j1( x );
 *
 *
 *
 * DESCRIPTION:
 *
 * Returns Bessel function of order one of the argument.
 *
 * The domain is divided into the intervals [0, 8] and
 * (8, infinity). In the first interval a 24 term Chebyshev
 * expansion is used. In the second, the asymptotic
 * trigonometric representation is employed using two
 * rational functions of degree 5/5.
 *
 *
 *
 * ACCURACY:
 *
 *                      Absolute error:
 * arithmetic   domain      # trials      peak         rms
 *    DEC       0, 30       10000       4.0e-17     1.1e-17
 *    IEEE      0, 30       30000       2.6e-16     1.1e-16
 *
 *
 */

/*
Cephes Math Library Release 2.8:  June, 2000
Copyright 1984, 1987, 1989, 2000 by Stephen L. Moshier
*/

#if FLOAT_SIZE>4
//Cephes double pression function

constant double RPJ1[8] = {
    -8.99971225705559398224E8,
    4.52228297998194034323E11,
    -7.27494245221818276015E13,
    3.68295732863852883286E15,
    0.0,
    0.0,
    0.0,
    0.0 };

constant double RQJ1[8] = {
    6.20836478118054335476E2,
    2.56987256757748830383E5,
    8.35146791431949253037E7,
    2.21511595479792499675E10,
    4.74914122079991414898E12,
    7.84369607876235854894E14,
    8.95222336184627338078E16,
    5.32278620332680085395E18
    };

constant double PPJ1[8] = {
    7.62125616208173112003E-4,
    7.31397056940917570436E-2,
    1.12719608129684925192E0,
    5.11207951146807644818E0,
    8.42404590141772420927E0,
    5.21451598682361504063E0,
    1.00000000000000000254E0,
    0.0} ;


constant double PQJ1[8] = {
    5.71323128072548699714E-4,
    6.88455908754495404082E-2,
    1.10514232634061696926E0,
    5.07386386128601488557E0,
    8.39985554327604159757E0,
    5.20982848682361821619E0,
    9.99999999999999997461E-1,
    0.0 };

constant double QPJ1[8] = {
    5.10862594750176621635E-2,
    4.98213872951233449420E0,
    7.58238284132545283818E1,
    3.66779609360150777800E2,
    7.10856304998926107277E2,
    5.97489612400613639965E2,
    2.11688757100572135698E2,
    2.52070205858023719784E1 };

constant double QQJ1[8] = {
    7.42373277035675149943E1,
    1.05644886038262816351E3,
    4.98641058337653607651E3,
    9.56231892404756170795E3,
    7.99704160447350683650E3,
    2.82619278517639096600E3,
    3.36093607810698293419E2,
    0.0 };

#pragma acc declare copyin( RPJ1[0:8], RQJ1[0:8], PPJ1[0:8], PQJ1[0:8], QPJ1[0:8], QQJ1[0:8])

#pragma acc routine seq
static
double cephes_j1(double x)
{

    double w, z, p, q, abs_x, sign_x;

    const double Z1 = 1.46819706421238932572E1;
    const double Z2 = 4.92184563216946036703E1;

    // 2017-05-18 PAK - mathematica and mpmath use J1(-x) = -J1(x)
    if (x < 0) {
        abs_x = -x;
        sign_x = -1.0;
    } else {
        abs_x = x;
        sign_x = 1.0;
    }

    if( abs_x <= 5.0 ) {
        z = abs_x * abs_x;
        w = polevl( z, RPJ1, 3 ) / p1evl( z, RQJ1, 8 );
        w = w * abs_x * (z - Z1) * (z - Z2);
        return( sign_x * w );
    }

    w = 5.0/abs_x;
    z = w * w;
    p = polevl( z, PPJ1, 6)/polevl( z, PQJ1, 6 );
    q = polevl( z, QPJ1, 7)/p1evl( z, QQJ1, 7 );

    // 2017-05-19 PAK improve accuracy using trig identies
    // original:
    //    const double THPIO4 =  2.35619449019234492885;
    //    const double SQ2OPI = 0.79788456080286535588;
    //    double sin_xn, cos_xn;
    //    SINCOS(abs_x - THPIO4, sin_xn, cos_xn);
    //    p = p * cos_xn - w * q * sin_xn;
    //    return( sign_x * p * SQ2OPI / sqrt(abs_x) );
    // expanding p*cos(a - 3 pi/4) - wq sin(a - 3 pi/4)
    //    [ p(sin(a) - cos(a)) + wq(sin(a) + cos(a)) / sqrt(2)
    // note that sqrt(1/2) * sqrt(2/pi) = sqrt(1/pi)
    const double SQRT1_PI = 0.56418958354775628;
    double sin_x, cos_x;
    SINCOS(abs_x, sin_x, cos_x);
    p = p*(sin_x - cos_x) + w*q*(sin_x + cos_x);
    return( sign_x * p * SQRT1_PI / sqrt(abs_x) );
}

#else
//Single precission version of cephes

constant float JPJ1[8] = {
    -4.878788132172128E-009,
    6.009061827883699E-007,
    -4.541343896997497E-005,
    1.937383947804541E-003,
    -3.405537384615824E-002,
    0.0,
    0.0,
    0.0
    };

constant float MO1J1[8] = {
    6.913942741265801E-002,
    -2.284801500053359E-001,
    3.138238455499697E-001,
    -2.102302420403875E-001,
    5.435364690523026E-003,
    1.493389585089498E-001,
    4.976029650847191E-006,
    7.978845453073848E-001
    };

constant float PH1J1[8] = {
    -4.497014141919556E+001,
    5.073465654089319E+001,
    -2.485774108720340E+001,
    7.222973196770240E+000,
    -1.544842782180211E+000,
    3.503787691653334E-001,
    -1.637986776941202E-001,
    3.749989509080821E-001
    };

#pragma acc declare copyin( JPJ1[0:8], MO1J1[0:8], PH1J1[0:8])

#pragma acc routine seq
static
float cephes_j1f(float xx)
{

    float x, w, z, p, q, xn;

    const float Z1 = 1.46819706421238932572E1;


    // 2017-05-18 PAK - mathematica and mpmath use J1(-x) = -J1(x)
    x = xx;
    if( x < 0 )
        x = -xx;

    if( x <= 2.0 ) {
        z = x * x;
        p = (z-Z1) * x * polevl( z, JPJ1, 4 );
        return( xx < 0. ? -p : p );
    }

    q = 1.0/x;
    w = sqrt(q);

    p = w * polevl( q, MO1J1, 7);
    w = q*q;
    // 2017-05-19 PAK improve accuracy using trig identies
    // original:
    //    const float THPIO4F =  2.35619449019234492885;    /* 3*pi/4 */
    //    xn = q * polevl( w, PH1J1, 7) - THPIO4F;
    //    p = p * cos(xn + x);
    //    return( xx < 0. ? -p : p );
    // expanding cos(a + b - 3 pi/4) is
    //    [sin(a)sin(b) + sin(a)cos(b) + cos(a)sin(b)-cos(a)cos(b)] / sqrt(2)
    xn = q * polevl( w, PH1J1, 7);
    float cos_xn, sin_xn;
    float cos_x, sin_x;
    SINCOS(xn, sin_xn, cos_xn);  // about xn and 1
    SINCOS(x, sin_x, cos_x);
    p *= M_SQRT1_2*(sin_xn*(sin_x+cos_x) + cos_xn*(sin_x-cos_x));

    return( xx < 0. ? -p : p );
}
#endif

#if FLOAT_SIZE>4
#define sas_J1 cephes_j1
#else
#define sas_J1 cephes_j1f
#endif

//Finally J1c function that equals 2*J1(x)/x
    
#pragma acc routine seq
static
double sas_2J1x_x(double x)
{
    return (x != 0.0 ) ? 2.0*sas_J1(x)/x : 1.0;
}


#endif // SAS_HAVE_sas_J1


#ifndef SAS_HAVE_gauss76
#define SAS_HAVE_gauss76

#line 1 "gauss76"
// Created by Andrew Jackson on 4/23/07

 #ifdef GAUSS_N
 # undef GAUSS_N
 # undef GAUSS_Z
 # undef GAUSS_W
 #endif
 #define GAUSS_N 76
 #define GAUSS_Z Gauss76Z
 #define GAUSS_W Gauss76Wt

// Gaussians
constant double Gauss76Wt[76] = {
	.00126779163408536,		//0
	.00294910295364247,
	.00462793522803742,
	.00629918049732845,
	.00795984747723973,
	.00960710541471375,
	.0112381685696677,
	.0128502838475101,
	.0144407317482767,
	.0160068299122486,
	.0175459372914742,		//10
	.0190554584671906,
	.020532847967908,
	.0219756145344162,
	.0233813253070112,
	.0247476099206597,
	.026072164497986,
	.0273527555318275,
	.028587223650054,
	.029773487255905,
	.0309095460374916,		//20
	.0319934843404216,
	.0330234743977917,
	.0339977794120564,
	.0349147564835508,
	.0357728593807139,
	.0365706411473296,
	.0373067565423816,
	.0379799643084053,
	.0385891292645067,
	.0391332242205184,		//30
	.0396113317090621,
	.0400226455325968,
	.040366472122844,
	.0406422317102947,
	.0408494593018285,
	.040987805464794,
	.0410570369162294,
	.0410570369162294,
	.040987805464794,
	.0408494593018285,		//40
	.0406422317102947,
	.040366472122844,
	.0400226455325968,
	.0396113317090621,
	.0391332242205184,
	.0385891292645067,
	.0379799643084053,
	.0373067565423816,
	.0365706411473296,
	.0357728593807139,		//50
	.0349147564835508,
	.0339977794120564,
	.0330234743977917,
	.0319934843404216,
	.0309095460374916,
	.029773487255905,
	.028587223650054,
	.0273527555318275,
	.026072164497986,
	.0247476099206597,		//60
	.0233813253070112,
	.0219756145344162,
	.020532847967908,
	.0190554584671906,
	.0175459372914742,
	.0160068299122486,
	.0144407317482767,
	.0128502838475101,
	.0112381685696677,
	.00960710541471375,		//70
	.00795984747723973,
	.00629918049732845,
	.00462793522803742,
	.00294910295364247,
	.00126779163408536		//75 (indexed from 0)
};

constant double Gauss76Z[76] = {
	-.999505948362153,		//0
	-.997397786355355,
	-.993608772723527,
	-.988144453359837,
	-.981013938975656,
	-.972229228520377,
	-.961805126758768,
	-.949759207710896,
	-.936111781934811,
	-.92088586125215,
	-.904107119545567,		//10
	-.885803849292083,
	-.866006913771982,
	-.844749694983342,
	-.822068037328975,
	-.7980001871612,
	-.77258672828181,
	-.74587051350361,
	-.717896592387704,
	-.688712135277641,
	-.658366353758143,		//20
	-.626910417672267,
	-.594397368836793,
	-.560882031601237,
	-.526420920401243,
	-.491072144462194,
	-.454895309813726,
	-.417951418780327,
	-.380302767117504,
	-.342012838966962,
	-.303146199807908,		//30
	-.263768387584994,
	-.223945802196474,
	-.183745593528914,
	-.143235548227268,
	-.102483975391227,
	-.0615595913906112,
	-.0205314039939986,
	.0205314039939986,
	.0615595913906112,
	.102483975391227,			//40
	.143235548227268,
	.183745593528914,
	.223945802196474,
	.263768387584994,
	.303146199807908,
	.342012838966962,
	.380302767117504,
	.417951418780327,
	.454895309813726,
	.491072144462194,		//50
	.526420920401243,
	.560882031601237,
	.594397368836793,
	.626910417672267,
	.658366353758143,
	.688712135277641,
	.717896592387704,
	.74587051350361,
	.77258672828181,
	.7980001871612,	//60
	.822068037328975,
	.844749694983342,
	.866006913771982,
	.885803849292083,
	.904107119545567,
	.92088586125215,
	.936111781934811,
	.949759207710896,
	.961805126758768,
	.972229228520377,		//70
	.981013938975656,
	.988144453359837,
	.993608772723527,
	.997397786355355,
	.999505948362153		//75
};


#pragma acc declare copyin(Gauss76Wt[0:76], Gauss76Z[0:76])

#endif // SAS_HAVE_gauss76


#ifndef SAS_HAVE_stacked_disks
#define SAS_HAVE_stacked_disks

#line 1 "stacked_disks"
static double
stacked_disks_kernel(
    double qab,
    double qc,
    double halfheight,
    double thick_layer,
    double radius,
    int n_stacking,
    double sigma_dnn,
    double core_sld,
    double layer_sld,
    double solvent_sld,
    double d)

{
    // q is the q-value for the calculation (1/A)
    // radius is the core radius of the cylinder (A)
    // *_sld are the respective SLD's
    // halfheight is the *Half* CORE-LENGTH of the cylinder = L (A)
    // zi is the dummy variable for the integration (x in Feigin's notation)

    const double besarg1 = radius*qab;
    //const double besarg2 = radius*qab;

    const double sinarg1 = halfheight*qc;
    const double sinarg2 = (halfheight+thick_layer)*qc;

    const double be1 = sas_2J1x_x(besarg1);
    //const double be2 = sas_2J1x_x(besarg2);
    const double be2 = be1;
    const double si1 = sas_sinx_x(sinarg1);
    const double si2 = sas_sinx_x(sinarg2);

    const double dr1 = core_sld - solvent_sld;
    const double dr2 = layer_sld - solvent_sld;
    const double area = M_PI*radius*radius;
    const double totald = 2.0*(thick_layer + halfheight);

    const double t1 = area * (2.0*halfheight) * dr1 * si1 * be1;
    const double t2 = area * dr2 * (totald*si2 - 2.0*halfheight*si1) * be2;

    double pq = square(t1 + t2);

    // loop for the structure factor S(q)
    double qd_cos_alpha = d*qc;
    //d*cos_alpha is the projection of d onto q (in other words the component
    //of d that is parallel to q.
    double debye_arg = -0.5*square(qd_cos_alpha*sigma_dnn);
    double sq=0.0;
    for (int kk=1; kk<n_stacking; kk++) {
        sq += (n_stacking-kk) * cos(qd_cos_alpha*kk) * exp(debye_arg*kk);
    }
    // end of loop for S(q)
    sq = 1.0 + 2.0*sq/n_stacking;

    return pq * sq * n_stacking;
    // volume normalization should be per disk not per stack but form_volume
    // is per stack so correct here for now.  Could change form_volume but
    // if one ever wants to use P*S we need the ER based on the total volume
}


static double
stacked_disks_1d(
    double q,
    double thick_core,
    double thick_layer,
    double radius,
    int n_stacking,
    double sigma_dnn,
    double core_sld,
    double layer_sld,
    double solvent_sld)
{
/*    StackedDiscsX  :  calculates the form factor of a stacked "tactoid" of core shell disks
like clay platelets that are not exfoliated
*/
    double summ = 0.0;    //initialize integral

    double d = 2.0*thick_layer+thick_core;
    double halfheight = 0.5*thick_core;

    for(int i=0; i<GAUSS_N; i++) {
        double zi = (GAUSS_Z[i] + 1.0)*M_PI_4;
        double sin_alpha, cos_alpha; // slots to hold sincos function output
        SINCOS(zi, sin_alpha, cos_alpha);
        double yyy = stacked_disks_kernel(q*sin_alpha, q*cos_alpha,
                           halfheight,
                           thick_layer,
                           radius,
                           n_stacking,
                           sigma_dnn,
                           core_sld,
                           layer_sld,
                           solvent_sld,
                           d);
        summ += GAUSS_W[i] * yyy * sin_alpha;
    }

    double answer = M_PI_4*summ;

    //Convert to [cm-1]
    return 1.0e-4*answer;
}

static double
form_volume_stacked_disks(
    double thick_core,
    double thick_layer,
    double radius,
    double fp_n_stacking)
{
    int n_stacking = (int)(fp_n_stacking + 0.5);
    double d = 2.0 * thick_layer + thick_core;
    return M_PI * radius * radius * d * n_stacking;
}

static double
Iq_stacked_disks(
    double q,
    double thick_core,
    double thick_layer,
    double radius,
    double fp_n_stacking,
    double sigma_dnn,
    double core_sld,
    double layer_sld,
    double solvent_sld)
{
    int n_stacking = (int)(fp_n_stacking + 0.5);
    return stacked_disks_1d(q,
                    thick_core,
                    thick_layer,
                    radius,
                    n_stacking,
                    sigma_dnn,
                    core_sld,
                    layer_sld,
                    solvent_sld);
}


static double
Iqac_stacked_disks(double qab, double qc,
    double thick_core,
    double thick_layer,
    double radius,
    double fp_n_stacking,
    double sigma_dnn,
    double core_sld,
    double layer_sld,
    double solvent_sld)
{
    int n_stacking = (int)(fp_n_stacking + 0.5);
    double d = 2.0 * thick_layer + thick_core;
    double halfheight = 0.5*thick_core;
    double answer = stacked_disks_kernel(qab, qc,
                     halfheight,
                     thick_layer,
                     radius,
                     n_stacking,
                     sigma_dnn,
                     core_sld,
                     layer_sld,
                     solvent_sld,
                     d);

    //convert to [cm-1]
    answer *= 1.0e-4;

    return answer;
}



#endif // SAS_HAVE_stacked_disks



/* END Required header for SASmodel stacked_disks */
%}
    DECLARE
%{
  double shape;
  double my_a_k;
%}

INITIALIZE
%{
shape=-1;  /* -1:no shape, 0:cyl, 1:box, 2:sphere  */
if (xwidth && yheight && zdepth)
    shape=1;
  else if (R > 0 && yheight)
    shape=0;
  else if (R > 0 && !yheight)
    shape=2;
  if (shape < 0)
    exit(fprintf(stderr, "SasView_model: %s: sample has invalid dimensions.\n"
                         "ERROR     Please check parameter values.\n", NAME_CURRENT_COMP));

  /* now compute target coords if a component index is supplied */
  if (!target_index && !target_x && !target_y && !target_z) target_index=1;
  if (target_index)
  {
    Coords ToTarget;
    ToTarget = coords_sub(POS_A_COMP_INDEX(INDEX_CURRENT_COMP+target_index),POS_A_CURRENT_COMP);
    ToTarget = rot_apply(ROT_A_CURRENT_COMP, ToTarget);
    coords_get(ToTarget, &target_x, &target_y, &target_z);
  }

  if (!(target_x || target_y || target_z)) {
    printf("SasView_model: %s: The target is not defined. Using direct beam (Z-axis).\n",
      NAME_CURRENT_COMP);
    target_z=1;
  }

  /*TODO fix absorption*/
  my_a_k = model_abs; /* assume absorption is given in 1/m */

%}


TRACE
%{
  double l0, l1, k, l_full, l, dl, d_Phi;
  double aim_x=0, aim_y=0, aim_z=1, axis_x, axis_y, axis_z;
  double f, solid_angle, kx_i, ky_i, kz_i, q, qx, qy, qz;
  char intersect=0;

  /* Intersection photon trajectory / sample (sample surface) */
  if (shape == 0){
    intersect = cylinder_intersect(&l0, &l1, x, y, z, kx, ky, kz, R, yheight);}
  else if (shape == 1){
    intersect = box_intersect(&l0, &l1, x, y, z, kx, ky, kz, xwidth, yheight, zdepth);}
  else if (shape == 2){
    intersect = sphere_intersect(&l0, &l1, x, y, z, kx, ky, kz, R);}
  if(intersect)
  {
    if(l0 < 0)
      ABSORB;

    /* Photon enters at l0. */
    k = sqrt(kx*kx + ky*ky + kz*kz);
    l_full = (l1 - l0);          /* Length of full path through sample */
    dl = rand01()*(l1 - l0) + l0;    /* Point of scattering */
    PROP_DL(dl);                     /* Point of scattering */
    l = (dl-l0);                   /* Penetration in sample */

    kx_i=kx;
    ky_i=ky;
    kz_i=kz;
    if ((target_x || target_y || target_z)) {
      aim_x = target_x-x;            /* Vector pointing at target (anal./det.) */
      aim_y = target_y-y;
      aim_z = target_z-z;
    }
    if(focus_aw && focus_ah) {
      randvec_target_rect_angular(&kx, &ky, &kz, &solid_angle,
        aim_x, aim_y, aim_z, focus_aw, focus_ah, ROT_A_CURRENT_COMP);
    } else if(focus_xw && focus_yh) {
      randvec_target_rect(&kx, &ky, &kz, &solid_angle,
        aim_x, aim_y, aim_z, focus_xw, focus_yh, ROT_A_CURRENT_COMP);
    } else {
      randvec_target_circle(&kx, &ky, &kz, &solid_angle, aim_x, aim_y, aim_z, focus_r);
    }
    NORM(kx, ky, kz);
    kx *= k;
    ky *= k;
    kz *= k;
    qx = (kx_i-kx);
    qy = (ky_i-ky);
    qz = (kz_i-kz);
    q = sqrt(qx*qx+qy*qy+qz*qz);
    
    double trace_thick_core=thick_core;
    double trace_thick_layer=thick_layer;
    double trace_radius=radius;
    if ( pd_thick_core!=0.0 || pd_thick_layer!=0.0 || pd_radius!=0.0 ){
    trace_thick_core = (randnorm()*pd_thick_core+1.0)*thick_core;
    trace_thick_layer = (randnorm()*pd_thick_layer+1.0)*thick_layer;
    trace_radius = (randnorm()*pd_radius+1.0)*radius;
    }

        
    double trace_theta=theta, dtheta=0.0;
    double trace_Phi=Phi, dPhi=0.0;
    if ( pd_theta!=0.0 || pd_Phi!=0.0 ){
    trace_theta = ((rand01()-0.5)*pd_theta + 1.0)*theta;
    dtheta = trace_theta-theta;
    trace_Phi = ((rand01()-0.5)*pd_Phi + 1.0)*Phi;
    dPhi = trace_Phi-Phi;
    }


    // Sample dependent. Retrieved from SasView./////////////////////
    float Iq_out;
    Iq_out = 1;

    double qab=0.0, qc=0.0;
    QACRotation rotation;

    qac_rotation(&rotation, trace_theta, trace_Phi, dtheta, dPhi);
    qac_apply(&rotation, qx, qy, &qab, &qc);
    Iq_out = Iqac_stacked_disks(qab, qc, trace_thick_core, trace_thick_layer, trace_radius, n_stacking, sigma_d, sld_core, sld_layer, sld_solvent );


    float vol;
    vol = 1;

    // Scale by 1.0E2 [SasView: 1/cm  ->   McXtrace: 1/m]
    Iq_out = model_scale*Iq_out / vol * 1.0E2;

    
    p *= l_full*solid_angle/(4*PI)*Iq_out*exp(-my_a_k*(l+l1));


    SCATTER;
  }
%}

MCDISPLAY
%{

  if (shape == 0) {	/* cylinder */
    circle("xz", 0,  yheight/2.0, 0, R);
    circle("xz", 0, -yheight/2.0, 0, R);
    line(-R, -yheight/2.0, 0, -R, +yheight/2.0, 0);
    line(+R, -yheight/2.0, 0, +R, +yheight/2.0, 0);
    line(0, -yheight/2.0, -R, 0, +yheight/2.0, -R);
    line(0, -yheight/2.0, +R, 0, +yheight/2.0, +R);
  }
  else if (shape == 1) { 	/* box */
    double xmin = -0.5*xwidth;
    double xmax =  0.5*xwidth;
    double ymin = -0.5*yheight;
    double ymax =  0.5*yheight;
    double zmin = -0.5*zdepth;
    double zmax =  0.5*zdepth;
    multiline(5, xmin, ymin, zmin,
                 xmax, ymin, zmin,
                 xmax, ymax, zmin,
                 xmin, ymax, zmin,
                 xmin, ymin, zmin);
    multiline(5, xmin, ymin, zmax,
                 xmax, ymin, zmax,
                 xmax, ymax, zmax,
                 xmin, ymax, zmax,
                 xmin, ymin, zmax);
    line(xmin, ymin, zmin, xmin, ymin, zmax);
    line(xmax, ymin, zmin, xmax, ymin, zmax);
    line(xmin, ymax, zmin, xmin, ymax, zmax);
    line(xmax, ymax, zmin, xmax, ymax, zmax);
  }
  else if (shape == 2) {	/* sphere */
    circle("xy", 0,  0.0, 0, R);
    circle("xz", 0,  0.0, 0, R);
    circle("yz", 0,  0.0, 0, R);
  }
%}
END