$diffusortype

$diffusortype is a special function to define the material parameters. Some materials are diffusive material so that we can apply the diffusor parameters.

The usage is

$diffusortype
type_1 diffusion_length_1
type_2 diffusion_length_2
...
...  totalregions
...
type_Nth diffusion_length_N

In side the diffusor, the program will decide if it will change location depending on diffusion length.

Type 1,  random diffusion
Type 2,  cos dependent
Type 3,  cos^2 dependent

       elseif(diffusortypess==1) then

           I=(1-exp(-1.0*compare(3)*diffusorlength))
           call random_number(diffusing)
           if(diffusing<I)then
             x=cx
             y=cy
             intersectionss=2
             call random_number(angle)
             vx=cos(angle*2*pi)
             vy=sin(angle*2*pi)
           end if
       elseif(diffusortypess==2) then
           I=(1-exp(-1.0*compare(3)*diffusorlength))
           call random_number(diffusing)
           if(diffusing<I)then
              x=cx
              y=cy
              intersectionss=2
              call random_number(angle)
              theta = (1-cos(angle*pi/2) )*pi/2
              call random_number(angle)
              if(angle .ne.0.5) then
                 theta= theta*(angle-0.5)/abs(angle-0.5)
              end if
              oldvx=vx
              oldvy=vy
              if(oldvy>0) then
                oldtheta=acos(oldvx/sqrt(oldvx*oldvx+oldvy*oldvy))
              elseif(oldvy==0.0) then
                 if(oldvx >0.0) oldtheta=0.0
                 if(oldvx <0.0) oldtheta=pi
              else
                oldtheta=2*pi-acos(oldvx/sqrt(oldvx*oldvx+oldvy*oldvy))
              end if

              vx=cos(theta+oldtheta)
              vy=sin(theta+oldtheta)
           end if
       elseif(diffusortypess==3) then
           I=(1-exp(-1.0*compare(3)*diffusorlength))
           call random_number(diffusing)
           if(diffusing<I)then
              x=cx
              y=cy
              intersectionss=2
              call random_number(angle)
              theta = (1-cos(angle*pi/2) )**2*pi/2
              call random_number(angle)
              if(angle .ne.0.5) then
                 theta= theta*(angle-0.5)/abs(angle-0.5)
              end if
              oldvx=vx
              oldvy=vy
              if(oldvy>0) then
                oldtheta=acos(oldvx/sqrt(oldvx*oldvx+oldvy*oldvy))
              elseif(oldvy==0.0) then
                 if(oldvx >0.0) oldtheta=0.0
                 if(oldvx <0.0) oldtheta=pi
              else
                oldtheta=2*pi-acos(oldvx/sqrt(oldvx*oldvx+oldvy*oldvy))
              end if

              vx=cos(theta+oldtheta)
              vy=sin(theta+oldtheta)

           end if

       end if