/*******************************************************************************
*
* McStas, the neutron ray-tracing package: Gravity_guide.comp
*         Copyright 1997-2001 Risoe National Laboratory, Roskilde, Denmark
*
* Component: Gravity_guide
*
* %I
* Written by: <a href="mailto:farhi@ill.fr">Emmanuel Farhi</a>
* Date: Aug 03 2001
* Version: $Revision: 1.18 $
* Origin: McStas 1.6/<a href="http://www.ill.fr">ILL (France)</a>.
* Modified by: E. Farhi, from Gravity_guide by K. Lefmann (buggy).
* Modified by: E. Farhi, focusing channels are now ok (Sept 4th, 2001).
* Modified by: EF, 2004. Renamed as Guide_gravity
*
* Neutron guide with gravity. Can be channeled and focusing.
*
* %D
* Models a rectangular guide tube centered on the Z axis. The entrance lies
* in the X-Y plane. Gravitation applies also when reaching the guide input
* window. The guide can be channeled (k,d parameters). The guide coating
* specifications may be entered via different ways (global, or for
* each wall m-value).
* The gravitation vector is downward in the local component coordinates.
* For details on the geometry calculation see the description in the McStas
* reference manual.
* OBSOLETE: rather use optics/Guide_gravity
*
* Example: Gravity_guide(w1=0.1, h1=0.1, w2=0.1, h2=0.1, l=12,
*           R0=0.99, Qc=0.021, alpha=6.07, m=1.0, W=0.003, k=1, d=0.0005)
*
* %P
* INPUT PARAMETERS:
*
* w1:      (m)    Width at the guide entry
* h1:      (m)    Height at the guide entry
* w2:      (m)    Width at the guide exit
* h2:      (m)    Height at the guide exit
* l:       (m)    length of guide
* R0:      (1)    Low-angle reflectivity
* Qc:      (AA-1) Critical scattering vector
* alpha:   (AA)   Slope of reflectivity
* m:       (1)    m-value of material. Zero means completely absorbing.
* W:       (AA-1) Width of supermirror cut-off
* d:       (m)    Thickness of subdividing walls [0]
* k:       (1)    Number of channels in the guide (>= 1) [1]
*
* Optional input parameters: (different ways for G and m-specifications)
*
* mleft:   (1)    m-value of material for left.   vert. mirror
* mright:  (1)    m-value of material for right.  vert. mirror
* mtop:    (1)    m-value of material for top.    horz. mirror
* mbottom: (1)    m-value of material for bottom. horz. mirror
*
* OUTPUT PARAMETERS
*
* Vars:             (1) internal variables
* Vars.N_reflection: (1) Array of the cumulated Number of reflections
*                   N_reflection[0] total nb of reflections
*                   N_reflection[1,2,3,4] l/r/t/b reflections
*                   N_reflection[5] total nb neutrons exiting guide
*                   N_reflection[6] total nb neutrons entering guide
*
* %D
* Example values: m=4 Qc=0.02 W=1/300 alpha=6.49 R0=1
*
* %E
*******************************************************************************/

DEFINE COMPONENT Gravity_guide
DEFINITION PARAMETERS ()
SETTING PARAMETERS (w1, h1, w2, h2, l,
  R0=0.99, Qc=0.021, alpha=6.07, m=1.0, W=0.003, k=1, d=0.0005,
  mleft=-1, mright=-1, mtop=-1, mbottom=-1)
OUTPUT PARAMETERS (Vars)
STATE PARAMETERS (x,y,z,vx,vy,vz,t,s1,s2,p)

SHARE
%{
#ifndef Gravity_guide_Version
#define Gravity_guide_Version "1.5"

#ifndef PROP_GRAV_DT
#error McStas : You need McStas >= 1.4.3 to run this component
#endif

/*
* G:       (m/sgn2) Gravitation acceleration along y axis [-9.81]
* Gx:      (m/sgn2) Gravitation acceleration along x axis [0]
* Gy:      (m/sgn2) Gravitation acceleration along y axis [-9.81]
* Gz:      (m/sgn2) Gravitation acceleration along z axis [0]
* mh:      (1)    m-value of material for left/right vert. mirrors
* mv:      (1)    m-value of material for top/bottom horz. mirrors
* mx:      (1)    m-value of material for left/right vert. mirrors
* my:      (1)    m-value of material for top/bottom horz. mirrors
*/

  typedef struct Gravity_guide_Vars
  {
    double gx;
    double gy;
    double gz;
    double nx[6], ny[6], nz[6];
    double wx[6], wy[6], wz[6];
    double A[6], norm_n2[6], norm_n[6];
    long   N_reflection[7];
    double w1c;
    double w2c;
    double M[5];
    double nzC[3], norm_n2c[3], Ac[3];
    double n_dot_v[6];
    char   compcurname[256];
  } Gravity_guide_Vars_type;

  void Gravity_guide_Init(Gravity_guide_Vars_type *aVars,
    MCNUM a_w1, MCNUM a_h1, MCNUM a_w2, MCNUM a_h2, MCNUM a_l, MCNUM a_R0,
    MCNUM a_Qc, MCNUM a_alpha, MCNUM a_m, MCNUM a_W, MCNUM a_k, MCNUM a_d,
    MCNUM a_Gx, MCNUM a_Gy, MCNUM a_Gz, MCNUM a_G, MCNUM a_mh, MCNUM a_mv,
    MCNUM a_mx, MCNUM a_my, MCNUM a_mleft, MCNUM a_mright, MCNUM a_mtop,
    MCNUM a_mbottom)
  {
    int i;

    for (i=0; i<7; aVars->N_reflection[i++] = 0);
    for (i=0; i<5; aVars->M[i++] = 0);

    aVars->gx = a_Gx; /* The gravitation vector in the current component axis system */
    if (a_G) aVars->gy = a_G; else aVars->gy = a_Gy;
    aVars->gz = a_Gz;

    if (a_k <= 0) { fprintf(stderr,"%s: Fatal: no channel in this guide (k=0).\n", aVars->compcurname); exit(-1); }
    if (a_d < 0) { fprintf(stderr,"%s: Fatal: subdividing walls have negative thickness in this guide (d<0).\n", aVars->compcurname); exit(-1); }
    aVars->w1c = (a_w1 + a_d)/(double)a_k;
    aVars->w2c = (a_w2 + a_d)/(double)a_k;

    for (i=0; i <= 4; aVars->M[i++]=a_m);
    if (a_mx >= 0) { aVars->M[1] =a_mx; aVars->M[2] =a_mx; }
    if (a_mv >= 0) { aVars->M[1] =a_mv; aVars->M[2] =a_mv; }
    if (a_my >= 0) { aVars->M[3] =a_my; aVars->M[4] =a_my; }
    if (a_mh >= 0) { aVars->M[3] =a_mh; aVars->M[4] =a_mh; }
    if (a_mleft   >= 0) aVars->M[1] =a_mleft  ;
    if (a_mright  >= 0) aVars->M[2] =a_mright ;
    if (a_mtop    >= 0) aVars->M[3] =a_mtop   ;
    if (a_mbottom >= 0) aVars->M[4] =a_mbottom;

    /* This is now the downward gravitation vector */

    aVars->nx[1] =  a_l; aVars->ny[1] =  0;   aVars->nz[1] = -0.5*(aVars->w2c-aVars->w1c); /* 1:+X left       */
    aVars->nx[2] =  a_l; aVars->ny[2] =  0;   aVars->nz[2] = -aVars->nz[1];  /* 2:-X right      */
    aVars->nx[3] =  0;   aVars->ny[3] =  a_l; aVars->nz[3] = -0.5*(a_h2-a_h1);   /* 3:+Y top        */
    aVars->nx[4] =  0;   aVars->ny[4] = -a_l; aVars->nz[4] =  aVars->nz[3];  /* 4:-Y bottom     */
    aVars->nx[5] =  0;   aVars->ny[5] =  0;   aVars->nz[5] =  1;             /* 5:+Z exit       */
    aVars->nx[0] =  0;   aVars->ny[0] =  0;   aVars->nz[0] = -1;             /* 0:Z0 input      */

    aVars->wx[1] = +(aVars->w1c-a_d)/2; aVars->wy[1] =  0;      aVars->wz[1] = 0;   /* 1:+X left       */
    aVars->wx[2] = -(aVars->w1c-a_d)/2; aVars->wy[2] =  0;      aVars->wz[2] = 0;   /* 2:-X right      */
    aVars->wx[3] =  0;                  aVars->wy[3] = +a_h1/2; aVars->wz[3] = 0;   /* 3:+Y top        */
    aVars->wx[4] =  0;                  aVars->wy[4] = -a_h1/2; aVars->wz[4] = 0;   /* 4:-Y bottom     */
    aVars->wx[5] =  0;                  aVars->wy[5] =  0;      aVars->wz[5] = a_l;   /* 5:+Z exit       */
    aVars->wx[0] =  0;                  aVars->wy[0] =  0;      aVars->wz[0] = 0;   /* 0:Z0 input      */

    for (i=0; i <= 5; i++)
    {
      aVars->A[i] = scalar_prod(aVars->nx[i], aVars->ny[i], aVars->nz[i], aVars->gx, aVars->gy, aVars->gz)/2;
      aVars->norm_n2[i] = aVars->nx[i]*aVars->nx[i] + aVars->ny[i]*aVars->ny[i] + aVars->nz[i]*aVars->nz[i];
      if (aVars->norm_n2[i] <= 0)
        { fprintf(stderr,"%s: Fatal: normal vector norm %i is null/negative ! Check guide dimensions.\n", aVars->compcurname, i); exit(-1); } /* should never occur */
      else
        aVars->norm_n[i] = sqrt(aVars->norm_n2[i]);
    }
    /* partial computations for l/r sides, to save computing time */
    aVars->nzC[1]      = aVars->nz[1];
    aVars->norm_n2c[1] = aVars->nx[1]*aVars->nx[1] + aVars->ny[1]*aVars->ny[1];
    aVars->Ac[1]       = aVars->nx[1]*aVars->gx    + aVars->ny[1]*aVars->gy;
    aVars->nzC[2]      = aVars->nz[2];
    aVars->norm_n2c[2] = aVars->nx[2]*aVars->nx[2] + aVars->ny[2]*aVars->ny[2];
    aVars->Ac[2]       = aVars->nx[2]*aVars->gx    + aVars->ny[2]*aVars->gy;
  }

  int Gravity_guide_Trace(double *dt, double *dt0,
        Gravity_guide_Vars_type *aVars,
        double cx, double cy, double cz,
        double cvx, double cvy, double cvz,
        double cnum, double ck)
  {
    double B, C, ret;
    int    side=0;
    double n1,n2;

    /* look if there is a previous intersection with guide sides */

    /* 3=+Y side: n=(0, l, -0.5*(h2-h1)) ; W = (0, +h1/2, 0) (up) */
    B = aVars->ny[3]*cvy + aVars->nz[3]*cvz; C = aVars->ny[3]*(cy-aVars->wy[3]) + aVars->nz[3]*cz; /* aVars->nx=aVars->wz=0 */
    ret = plane_intersect_Gfast(dt0, aVars->A[3], B, C);
    if (ret && *dt0>10e-10 && *dt0<*dt)
    { *dt = *dt0; side=3; aVars->n_dot_v[3] = B; }

    /* 4=-Y side: n=(0, l, +0.5*(h2-h1)) ; W = (0, -h1/2, 0) (down) */
    B = aVars->ny[4]*cvy + aVars->nz[4]*cvz; C = aVars->ny[4]*(cy-aVars->wy[4]) + aVars->nz[4]*cz; /* aVars->nx=aVars->wz=0 */
    ret = plane_intersect_Gfast(dt0, aVars->A[4], B, C);
    if (ret && *dt0>10e-10 && *dt0<*dt)
    { *dt = *dt0; side=4; aVars->n_dot_v[4] = B; }

    /* 1=+X side: n=(l, 0, -0.5*(w2-w1)) ; W = (+w1/2, 0, 0) (left)*/
    if (aVars->nzC[1] != 0) {
      n1 = 2*(cnum+1) - ck;  /* slope of l/r sides depends on the channel ! */
      aVars->nz[1] = aVars->nzC[1]*n1;
      aVars->A[1] = aVars->Ac[1] + aVars->nz[1]*aVars->gz; }
    B = aVars->nx[1]*cvx + aVars->nz[1]*cvz; C = aVars->nx[1]*(cx-aVars->wx[1]) + aVars->nz[1]*cz; /* aVars->ny=aVars->wz=0 */
    ret = plane_intersect_Gfast(dt0, aVars->A[1], B, C);
    if (ret && *dt0>10e-10 && *dt0<*dt)
    { *dt = *dt0; side=1; aVars->n_dot_v[1] = B;
      if (aVars->nzC[1] != 0)
      { aVars->norm_n2[1] = aVars->norm_n2c[1] + aVars->nz[1]*aVars->nz[1]; aVars->norm_n[1] = sqrt(aVars->norm_n2[1]);}
    }

    /* 2=-X side: n=(l, 0, +0.5*(w2-w1)) ; W = (-w1/2, 0, 0) (right) */
    if (aVars->nzC[1] != 0) {
      n2 = 2*(cnum) - ck;  /* slope of l/r sides depends on the channel ! */
      aVars->nz[2] = aVars->nzC[1]*n2; }
    aVars->A[2] = aVars->Ac[2] + aVars->nz[2]*aVars->gz;
    B = aVars->nx[2]*cvx + aVars->nz[2]*cvz; C = aVars->nx[2]*(cx-aVars->wx[2]) + aVars->nz[2]*cz; /* aVars->ny=aVars->wz=0 */
    ret = plane_intersect_Gfast(dt0, aVars->A[2], B, C);
    if (ret && *dt0>10e-10 && *dt0<*dt)
    { *dt = *dt0; side=2; aVars->n_dot_v[2] = B;
      if (aVars->nzC[1] != 0)
      { aVars->norm_n2[2] = aVars->norm_n2c[2] + aVars->nz[2]*aVars->nz[2]; aVars->norm_n[2] = sqrt(aVars->norm_n2[2]); }
    }

    return (side);
  }
#endif
%}

DECLARE
%{
  Gravity_guide_Vars_type Vars;
%}

INITIALIZE
%{
  double Gx=0, Gy=-9.81, Gz=0, G=-9.81;
  double mh=-1,mv=-1,mx=-1, my=-1;

  if (W < 0 || k <= 0 || R0 < 0 || Qc < 0)
  { fprintf(stderr,"Gravity_guide: %s W k R0 Qc must be >0.\n", NAME_CURRENT_COMP);
    exit(-1); }

  strcpy(Vars.compcurname, NAME_CURRENT_COMP);
  Gravity_guide_Init(&Vars,
  w1, h1, w2, h2, l, R0,
  Qc, alpha, m, W, k, d,
  Gx, Gy, Gz, G, mh, mv,
  mx, my, mleft, mright, mtop,
  mbottom);

%}

TRACE
%{
  double B, C, dt0, dt;
  double q;
  int    ret, side, side0;
  double edge;
  double hadj;    /* Channel displacement */
  double n1, n2, Ch_num;
  int    bounces = 0;


  dt = -1; dt0 = -1;
  /* propagate to box input (with gravitation) in comp local coords */
  /* 0=Z0 side: n=(0, 0, 1) ; W = (0, 0, 0) (at z=0, guide input)*/
  B = -vz; C = -z;

  ret = plane_intersect_Gfast(&dt0, Vars.A[0], B, C);
  if (ret && dt0>0)
  {
    dt = dt0;
    PROP_GRAV_DT(dt, Vars.gx, Vars.gy, Vars.gz);
    Vars.N_reflection[6]++;
  }
  /* check if we are in the box input, else absorb */
  if(dt > 0 && fabs(x) <= w1/2 && fabs(y) <= h1/2)
  {
    /* Shift origin to center of channel hit (absorb if hit dividing walls) */
    x += w1/2.0;
    Ch_num = floor(x/Vars.w1c);  /* 0= right side, k+1=left side  */
    edge = Ch_num*Vars.w1c;
    if(x - edge > Vars.w1c - d)
    {
      x -= w1/2.0; /* Re-adjust origin */
      ABSORB;
    }
    x -= (edge + (Vars.w1c - d)/2.0);
    hadj = edge + (Vars.w1c - d)/2.0 - w1/2.0;

    /* neutron is now in the input window of the guide */

    /* do loops on reflections in the box */
    for(;;)
    {
      /* get intersections for all box sides */
      /* A = 0.5 n.g; B = n.v; C = n.(r-W); */

      bounces++;

      side = 0;
      /* starts with the exit side intersection (the last one !)*/
      /* 5=+Z side: n=(0, 0, 1) ; W = (0, 0, l) (at z=l, guide exit)*/
      B = vz; C = z - Vars.wz[5];
      ret = plane_intersect_Gfast(&dt0, Vars.A[5], B, C);
      if (ret && dt0>0)
      { dt = dt0; side=5;
        Vars.n_dot_v[5] = B; }
      else
      { fprintf(stderr,"%s: warning: neutron trajectory is parallel to guide exit, and thus can not exit\n", Vars.compcurname); x += hadj; ABSORB; }

      /* now look if there is a previous intersection with guide sides */
      side0 = Gravity_guide_Trace(&dt, &dt0, &Vars, x, y, z,
          vx, vy, vz, Ch_num, k);
      if (side0) side= side0;

      /* only positive dt are valid */
      /* exit reflection loops if no intersection (neutron is after box) */
      if (side == 0 || dt < 0)
        { fprintf(stderr,"%s: warning: neutron has entered guide, but can not exit !\n", Vars.compcurname); x += hadj; ABSORB; } /* should never occur */
       /*
      if (side < 5 && (x < -w1 || x > w1 || y < -h1 || y > h2 ))
        ABSORB;  */ /* neutron has left guide through wall */

      /* propagate to dt */
      PROP_GRAV_DT(dt, Vars.gx, Vars.gy, Vars.gz);

      /* do reflection on speed for l/r/u/d sides */
      if (side == 5) /* neutron reaches end of guide: end loop and exit comp */
        { Vars.N_reflection[side]++; x += hadj; SCATTER; x -= hadj; break; }
      /* else reflection on a guide wall */
      if(Vars.M[side] == 0 || Qc == 0)  /* walls are absorbing */
        { x += hadj; ABSORB; }
      /* change/mirror velocity: v_f = v - n.2*n.v/|n|^2 */
      Vars.N_reflection[side]++; /* Vars.norm_n2 > 0 was checked at INIT */
      dt0 = 2*Vars.n_dot_v[side]/Vars.norm_n2[side]; /* 2*n.v/|n|^2 */
      vx -= Vars.nx[side]*dt0;
      vy -= Vars.ny[side]*dt0;
      vz -= Vars.nz[side]*dt0;

      /* compute q and modify neutron weight */
      /* scattering q=|k_i-k_f| = V2Q*|vf - v| = V2Q*2*n.v/|n| */
      q = 2*V2Q*fabs(Vars.n_dot_v[side])/Vars.norm_n[side];
      B = R0;
      if(q > Qc)
      {
        double arg;
        if (W>0)
          arg = (q-Vars.M[side]*Qc)/W;
        else
          arg = (q-Vars.M[side]*Qc)*10000; /* W = 0.00001 */

        if(arg < 10)
        {
          B *= .5*(1-tanh(arg))*(1-alpha*(q-Qc));
        }
        else
          { x += hadj; ABSORB; }; /* Cutoff ~ 1E-10 */
       }
       if (B < 0) B=0;
       if (B > 1) B=1;
       p *= B;
       x += hadj; SCATTER; x -= hadj;
       Vars.N_reflection[0]++;
       /* go to the next reflection */
       if (bounces > 1000) ABSORB;
     } /* end for */
      x += hadj; /* Re-adjust origin after SCATTER */
    }
    else
      ABSORB;
%}

MCDISPLAY
%{
  double x;
  int i;

  magnify("xy");
  for(i = 0; i < k; i++)
  {
    multiline(5,
              i*Vars.w1c - w1/2.0, -h1/2.0, 0.0,
              i*Vars.w2c - w2/2.0, -h2/2.0, (double)l,
              i*Vars.w2c - w2/2.0,  h2/2.0, (double)l,
              i*Vars.w1c - w1/2.0,  h1/2.0, 0.0,
              i*Vars.w1c - w1/2.0, -h1/2.0, 0.0);
    multiline(5,
              (i+1)*Vars.w1c - d - w1/2.0, -h1/2.0, 0.0,
              (i+1)*Vars.w2c - d - w2/2.0, -h2/2.0, (double)l,
              (i+1)*Vars.w2c - d - w2/2.0,  h2/2.0, (double)l,
              (i+1)*Vars.w1c - d - w1/2.0,  h1/2.0, 0.0,
              (i+1)*Vars.w1c - d - w1/2.0, -h1/2.0, 0.0);
  }
  line(-w1/2.0, -h1/2.0, 0.0, w1/2.0, -h1/2.0, 0.0);
  line(-w2/2.0, -h2/2.0, (double)l, w2/2.0, -h2/2.0, (double)l);
%}

END
