Primitives

• This must not modify the xCONS nemory (e.g. by requesting titles) because it may be passed sections of titles banks which might be invalid if memory relocation occurred. This rule should be accademic; the primitive will be passed all required information.

• Calling sequence:

  call gep_* ( irq_typ, iprm_typ, iprm_opr, isrf_base,
                                    prm_data, xyz_de, uvw_de )
  

  Parameters (all input only)

  
  
  
  irq_typ 		  Request type: see mnemonics Request Types (will 
  
  
  only be _NEXT, _NEAR or _PICK).
  
  
  iprm_typ 		  Primitive type: see mnenomics Primitive Types.
  
  
  iprm_opr 		  Primitive operation: see mnemonics flags.
  
  
  isrf_base 		  Base number for surfaces: add to internal surface
  
  
  number before storing in gep_current.inc
  
  
  prm_data 		  Primitive data: see Companion/Titles Banks/GEDS
  
  
  xyz_de 		  Particle position in detector element coordinates
  
  
  uvw_de 		  Particle direction cosines in detector element coordinates.
  
  
  

• Specification:-
  1. If debugging, check parameters:-

     *IF GE_DEBUG THEN
      
       Check request type, primitive type and operation.
       As far as reasonable, check primitive data.
      
     *ENDIF
     

  2. Use data for ge_current.inc as appropriate for current task.

  3. For request type:-

     KGE_NEXT

     find all boundary intersections (positive and negative) with current point and direction. Find also the surface numbers and boundary normals of these intersections.

     KGE_NEAR

     find nearest boundary using sign convention: -ve if inside primitive and +ve if outside. For complex shapes finding the exact distance to the nearest boundary can be very time consuming and isn't necessary, all that is required is that the sign be correct and that the distance given is not an overestimate. So an underestimate is acceptable and is often far easier to calculate.

     KGE_PICK

     select point randomly within primitive.

     Store results in gep_current.inc and then call boundary manager:-

     call geb_add_gep( irq_typ, iprm_opr )
     

Notes

1. The code can ignore the value of iprm_opr but the boundary manager needs to know if ORing or NOTing.

2. Adding the base number to the internal surface number ensures that each surface in the detector element is unique.

The following section lists the primitives available and their characteristics. The data words for each refer to the primitive data section of a GEDS bank and the location of the origin of the primitive coordinate system is also specified. On the diagrams the origin is marked by a cross within a circle, the surface numbers (used within the geometry code) by S1, S2 etc. and the lengths and angles corresponding to data words by simple numbers. See section 13 for a set of formulae that underpin the implimentation of these primitives.

     Sphere 




Filename:- 		  gep_sphere.for 		 		 


Data Words:- 		  1 Relative volume 		 		 


2 Radius 		 		 


Origin:- 		  At the centre of the sphere  

Usage:- The two surfaces of the acrylic vessel or , if acrylic tiles are activated then spheres form the boundaries of the glue in which the tiles are embedded.

Notes:- None needed

     Cylinder 




Filename:- 		  gep_cylinder.for 		 		 


Data Words:- 		  1 Relative volume 		 		 


2 Radius 		 		 


3 Half the height 		 		 


Origin:- 		  At the centre of the cylinder  

Usage:- The acrylic chimney, belly ropes and assorted calibration sources.

Notes:- None needed.

     Elliptical Cylinder 




Filename:- 		  gep_ellip_cylinder.for 		 		 


Data Words:- 		  1 Relative volume 		 		 


2 Length of the X semi-axis 		 		 


3 Length of the Y semi-axis 		 		 


4 Half the height 		 		 


Origin:- 		  At the centre of the elliptical 		 		 


cylinder  

Usage:- The rope grooves in the belly plates.

Notes:- None needed

     Block 




Filename:- 		  gep_block.for 		 		 


Data Words:- 		  1 Relative volume 		 		 


2 Half the length of the X side 		 		 


3 Half the length of the Y side 		 		 


4 Half the length of the Z side 		 		 


Origin:- 		  At the centre of the block  

Usage:- The rope grooves in the belly plates.

Notes:- None needed

     Octahedron 




Filename:- 		  gep_octahedron.for 		 		 


Data Words:- 		  1 Relative volume 		 		 


2 Length from centre to apex 		 		 


in Z direction 		    


3 Tangent of angle between 		 		 


XY plane and plane faces 		    


Origin:- 		  At the centre of the octahedron  

Usage:- The bevelled sides of the belly plates.

Notes:- None needed

     Half Torus 




Filename:- 		  gep_half_torus.for 		 		 


Data Words:- 		  1 Relative volume 		 		 


2 Radius of the circular 		 		 


cross-section 		    


3 Major radius to the centre 		 		 


of the circular cross-section 		    


Origin:- 		  At centre of the corresponding 		 		 


full torus  

Usage:- The belly plate ropes.

Notes:- None needed

     Half Elliptical Torus 




Filename:- 		  gep_half_ellip_torus.for 		 		 


Data Words:- 		  1 Relative volume 		 		 


2 X semi-axis of the elliptical 		 		 


cross-section 		    


3 Z semi-axis of the elliptical 		 		 


cross-section 		    


4 Major radius to the centre of 		 		 


the elliptical cross-section 		    


Origin:- 		  At centre of the corresponding 		 		 


full elliptical torus  

Usage:- The rope grooves in the belly plates.

Notes:- None needed

     Half Square Torus 




Filename:- 		  gep_half_square_torus.for 		 		 


Data Words:- 		  1 Relative volume 		 		 


2 X half length of the rectangular 		 		 


cross-section 		    


3 Z half length of the rectangular 		 		 


cross-section 		    


3 Major radius to the centre of 		 		 


the rectangular cross-section 		    


Origin:- 		  At centre of the corresponding 		 		 


full square torus  

Usage:- The rope grooves in the belly plates.

Notes:- None needed

     Spherical Tile 




Filename:- 		  gep_spherical_tile.for 		 		 


Data Words:- 		  1 Relative volume 		 		 


2 Radius to centre of tile 		 		 


3 Half width of tile 		 		 


4 TANGENT of angle between the 		 		 


XY plane and top of the tile 		    


5 TANGENT of angle between the 		 		 


XY plane and bottom of tile 		    


6 Angular half breadth of tile 		 		 


in XY plane (in radians) 		    


Origin:- 		  At centre of the sphere from 		 		 


which the tile is cut  

Usage:- The acrylic vessel tiles.

Notes:- The spherical tile is a section of a sphere between two constant azimuthal and two constant polar angles. the polar angles are taken from the XY plane, however, not from the Z axis.

     Frustum of Cone 




Filename:- 		  gep_frustum_of_cone.for 		 		 


Data Words:- 		  1 Relative volume 		 		 


2 Radius of the top plane (S1) 		 		 


3 Radius of the bottom plane (S3) 		 		 


4 Half the height 		 		 


Origin:- 		  At centre of the frustum  

Usage:- Assorted calibration sources.

Notes:- The functionality of the code requires that the radius of the top plane be greather than the radius of the bottom plane i.e. $r_{1} > r_{2}$. The desired orientation of the primitive is achived with the rotation matrix.