anchor.diff:  ")
   
   (defparameter +sphere-template+ "sphere {
  -  <~F,~F,~F>,0.5
  +  <~F,~F,~F>,0.25
     texture {
       pigment { color Yellow }
     }
  
positive.code: (defglobal size-y int)
  (defglobal size-z int)
  
  (defparameter h           0.01)
  (defparameter pmass       0.00020543)
  (defparameter simscale    0.004)
  (defparameter restdensity 600.0)
  (defparameter pdist       (expt (/ pmass restdensity) (/ 1.0 3.0)))
  (defparameter g           (make-float4 0.0 -9.8 0.0 0.0))
  (defparameter delta       (/ h simscale))
  (defparameter box-min     (make-float4  0.0  0.0 -10.0 0.0))
  (defparameter box-max     (make-float4 20.0 50.0  10.0 0.0))
  (defparameter init-min    (make-float4  0.0  0.0 -10.0 0.0))
  (defparameter init-max    (make-float4 10.0 20.0  10.0 0.0))
  (defparameter capacity    20)   ; # of particles contained in one cell
  
  
  ;;
  
negative.code: ;;
  ;; Parameters
  
  (defglobal h float 0.005)
  (defglobal dt float 0.0004)
  (defglobal pi float 3.1415927)
  (defglobal visc float 0.2)
  (defglobal limit float 200.0)
  (defglobal pmass float (/ 0.00020543 8.0))
  (defglobal radius float 0.002)
  (defglobal epsilon float 0.00001)
  (defglobal extdamp float 512.0)
  (defglobal simscale float 0.004)
  (defglobal intstiff float 3.0)
  (defglobal extstiff float 20000.0)
  (defglobal restdensity float 600.0)
  (defglobal g float4)
  (defglobal box-min float4)
  