/*******************************************************************************
*
* McStas, neutron ray-tracing package
*         Copyright 1997-2002, All rights reserved
*         Risoe National Laboratory, Roskilde, Denmark
*         Institut Laue Langevin, Grenoble, France
*
* Component: Slit
*
* %I
* Written by: Kim Lefmann and Henrik M. Roennow
* Date: June 16, 1997
* Version: $Revision: 1.21 $
* Origin: Risoe
* Release: McStas 1.6
*
* Rectangular/circular slit with optional insignificance cut
*
* %D
* A simple rectangular or circular slit. You may either 
* specify the radius (circular shape), or the rectangular bounds.
* No transmission around the slit is allowed.
* If cutting option is used, low-weight neutron rays are ABSORBED
*
* Example: Slit(xmin=-0.01, xmax=0.01, ymin=-0.01, ymax=0.01)
*          Slit(radius=0.01, cut=1e-10)
*
* %P
* INPUT PARAMETERS
*
* radius: Radius of slit in the z=0 plane, centered at Origo (m)
* xmin: Lower x bound (m)
* xmax: Upper x bound (m)
* ymin: Lower y bound (m)
* ymax: Upper y bound (m)
*
* Optional parameters:
* cut:  Lower limit for allowed weight (1)
*
* %E
*******************************************************************************/


DEFINE COMPONENT Slit
DEFINITION PARAMETERS ()
SETTING PARAMETERS (xmin=0, xmax=0, ymin=0, ymax=0, radius=0, cut=0)
STATE PARAMETERS (x,y,z,vx,vy,vz,t,s1,s2,p)

INITIALIZE
%{
  if (xmin == 0 && xmax == 0 && ymin == 0 && ymax == 0 && radius == 0)
    { fprintf(stderr,"Slit: %s: Error: give geometry\n", NAME_CURRENT_COMP); exit(-1); }
  
%}

TRACE
%{
    PROP_Z0;
    if (((radius == 0) && (x<xmin || x>xmax || y<ymin || y>ymax))
    || ((radius != 0) && (x*x + y*y > radius*radius)))
      ABSORB;
    else
      if (p < cut)
        ABSORB;
      else
        SCATTER;
%}

MCDISPLAY
%{
  double xw, yh;
  magnify("xy");
  xw = (xmax - xmin)/2.0;
  yh = (ymax - ymin)/2.0;
  multiline(3, xmin-xw, (double)ymax, 0.0,
            (double)xmin, (double)ymax, 0.0,
            (double)xmin, ymax+yh, 0.0);
  multiline(3, xmax+xw, (double)ymax, 0.0,
            (double)xmax, (double)ymax, 0.0,
            (double)xmax, ymax+yh, 0.0);
  multiline(3, xmin-xw, (double)ymin, 0.0,
            (double)xmin, (double)ymin, 0.0,
            (double)xmin, ymin-yh, 0.0);
  multiline(3, xmax+xw, (double)ymin, 0.0,
            (double)xmax, (double)ymin, 0.0,
            (double)xmax, ymin-yh, 0.0);
%}

END
