Sorry to have to bother you again with this clumsy model of the sceptre of
Catherine the Great. But we had some discussions about resuming a rendering in
the beta-test section (a thread from Chaanakya with the subject: Resuming
renders in 3.7 RC6 is confusing at best, broken at worst) and Alain wasn't sure
about the behaviour of POV in scenes using photons. Having this image handy with
reasonable rendering times even on an older dual core pentium, I tried resuming
it after having saved the photon map. I tried two different versions of the
picture. One with a simple sky_sphere (I think it is the one from the examples
of the tutorial):

#declare Himmel = sky_sphere {
  pigment {
     gradient y
     color_map {
        [ 0.5  color CornflowerBlue ]
        [ 1.0  color MidnightBlue ]
     }
     scale 2
     translate -1
  }
}

and the second one with my first attempt with (Pseudo?-) HDRI lighting:

#declare kitchen=sphere {<0, 1, 0>, 650
   texture {
      pigment {
         image_map {
            hdr "thekitchen.hdr"
            once
            interpolate 2
            map_type 1
         }
         rotate <0, -30-135+(16*15), 0> // window is at -30 behind the camera
                                        // attuned to the light source
         scale 1
      }
      finish { emission Bright/2 diffuse 0 }
   }
   hollow
   photons { refraction on reflection on }
}

It is very likely that I misunderstood somehing here. At the moment I'm not
quiete sure where I've stolen the code, but I think it's Jaime's Pseudo-HDRI
approach. But the main fact with this issue here is that I didn't change the
lighting between the resumes. In both examples I stopped and resumed the
rendering at the first block at the shaft and a second time in the near of the
globus cruciger. The first picture here with the simple sky_sphere shows no
flaws but the second one with Jaime's thekitchen.hdr sows strange changes in
color at the points I stopped and resumed the rendering. Has anyone an idea?
Feel free for criticism.

Best regards,
Michael

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