From section 3.6.3.2.2 of the documentation


automatically. You can then turn off pass_through if necessary by simply
using photons { pass_through off }.


This is exactly what I am trying to do, but it does not seem to work for me.
 I'm using Povray 3.6.1

I've created a small scene below, a glass sphere on a plane, to demonstrate
this.

With the no_shadow modifier present, no caustics (and no shadow) are visible
on the plane.  Whereas I was expecting to see caustics on the plane (having
explicitly turned pass_though off in the objects photon block) but no
shadow.

If you comment out the no_shadow line, caustics (and the shadow) are visible
on the plane.

Am I doing something wrong?

Here is the scene.

#include "textures.inc"

global_settings {
      photons { count 20000 autostop 1 }
}

camera {
  location  <0.25, 1.5, -2.0>
  direction 1.5*z
  look_at   <0.25, 0.5,  0.0>
}

light_source {
  <0, 0, 0>
  color rgb <1, 1, 1>
  translate <-30, 30, 0>
  photons {
    refraction on
    reflection on
  }
}

sphere {
 <0,0,0> .5
 no_shadow // enabling no_shadow automatically tags object as pass_through
(3.6.3.2.2)
 material { M_Glass3 }

 photons{
  target
  reflection on
  refraction on
  collect off
  pass_through off // explicitly turn pass_through off
 }
 translate <0,.5,0>
}

plane {  y, -.2  pigment { color rgb <1,1,1> } }

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