I am trying to emulate an optics table.  I need narrow cylindrical beams of
light, that reflect off mirrors and refract through lenses and interact with
the media in a 'fog box'. I am /almost/ there.

I've tried everything I can think of to get a laser beam effect that has
photon interaction with media. The following works, but /only/ with a
spotlight.  When I use a cylindrical light, the refracted (or reflected)
photons stop interacting with the media.  Any ideas?

BTW, the parallel modifier causes /all/ the media to light up. Sigh.

My understanding is shrinking along with any ego I might have previously
possessed. My wife is going home to mama.  My mortgage is in arrears. My
hair is gone. I giggle a lot, then burst into uncontrolled tears. I am
hopelessly addicted.
--------------------------------------
#version 3.5;

#include "colors.inc"
#include "textures.inc"

global_settings {
  assumed_gamma 1
  max_trace_level 25

  photons {
    spacing 0.03
    media 100
    autostop 0
    jitter 0
  }
}

light_source {
    <0, 30, 0> *2
    color White * 1
}

camera {
    orthographic
    location <0,17,0>
    look_at <0,0,0>
}

box { // fog box
    <-9,-2,-9>,<9,2,9>
    pigment { White filter 1 }
    hollow on
    photons {pass_through}
    interior{
        media {
        scattering { 1, rgb 0.03}
        intervals 1
        samples 5
        method 3
        }

    }
}

    light_source {  //spotlight
        0*x
        color Green * 3
        //cylinder
        spotlight
        translate <-15,.5,4>
        point_at <0,.5,4>
        radius 1
        tightness 90
        falloff 5
        photons {
            refraction on
            reflection on
        }
    }

intersection {// lens
    intersection {
        sphere {
            <0, 4.95, 0>, 5
        }
        sphere {
            <0, -4.95, 0>, 5
        }
        scale <1,1,1> * 8
    }
    cylinder {
        <0, 3, 0>,
        <0, -3, 0>,
        7.0
    }
    material {
      M_NB_Glass
    }
    photons {
        target
        refraction on
        reflection off
    }

    rotate z*90
    translate -x * 7
}

--------------------------------------

Alan Walkington

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