Don Barron wrote:
>Does anyone know how to simulate the vignetting that was present in old
>camera lenses - a loss of brightness towards the edge of the field, say
>according to a cosine law?
>/* Simulating vignetting in the camera lens.
   Just a comment...   it's vignetting in the lens design and fabrication
which early lenses
   had, to reduce the serious image aberrations from the primitive lenses of
the time.
   ..the cos^4 effect is something else, but all the same...

   thanks to SLIME for the suggestion of a textured microscopic sphere
enclosing the
   camera.  This is his pov file but with a while loop inside
   the pigment color_map and a similar color_map applied to his object
sphere. Nice one...
*/

#declare A=67;       // angle
#declare R=<10,0,0>; // orientation
#declare L=<0,0,-5>; // location
#declare V=A; // variable, degrees? probably still not true to the real
world(?)

camera {location 0 look_at z angle 1.3*A rotate R    translate L   }


sphere { 0,1 pigment { cylindrical color_map { #declare Rho = 0;
                                                    #while (Rho <=1)
                                                         #declare TRho =
pow(cos(pi/2*Rho),4);
                                                        [ Rho color rgb 0
transmit TRho]
                                                        #debug concat("
",str(TRho,9,3),"\n")
                                                        #declare Rho = Rho +
0.1;
                                                    #end
                                             }
                       frequency -1 rotate 90*x
                     }
               finish{ ambient 0 diffuse 0 }
               scale 0.0001
               rotate R translate L
       }

sphere { 0,1 pigment { cylindrical color_map { #declare Rho = 0; #declare
Steps = 12;
                                               #while (Rho <=1)
                                                   #declare TRho =
pow(cos(pi/2*Rho),1);
                                                   [ Rho color rgb 0
transmit TRho]
                                                   #declare Rho = Rho +
1/Steps;
                                                   #end
                                             }
                       frequency -1 rotate 90*x
                     }
               finish{ ambient 0 diffuse 0 }
         rotate y*15 rotate -x*25
       }


sky_sphere { pigment { gradient y  color_map { [0 rgb <0.7,0.8,0.9>]
                                               [1 rgb <0.2,0.5,0.8>]
                                             }
                     }
           }

light_source { <-30, 30, -30>,1 }
plane { y,-1  pigment {color rgb 1} }

Post a reply to this message