news:web.41360476d5f46917a3fcf12a0@news.povray.org...
> I am having strange shadows appear on my image that I can't explain, and
> that seem to change and/or disappear under different conditions, as I will
> explain in more detail below. First, here is the entire image, so you can
> see the problem:

There's indeed something weird. Apparently, turning off the light buffers
fixes it (-UL) but it still looks like a bug.

Here's a much simplified version that shows the problem. It's apparent when
you compare the full render with the partial render +sc0.358121 +sr0.026110
+ec0.532290 +er0.258486
The shadow on the sphere is truncated on the full render and correct in the
partial one. The incomplete shadows cause the banding you see on your other
images.

Perhaps you can try to simplify it even more to see if it wouldn't be caused
by a coincident surfaces problem. If nobody comes up with an explanation,
you may file a bug report (see the guidelines).

#include "colors.inc"
//global_settings{max_trace_level 100}
camera {location  <4.5, 5.5, -7> look_at <0.5, 2.5,  0>}
light_source {<10, 50, -16>  color 2}
box {<-2, 0, 5>,<4, 6, 5.01> texture {finish {reflection 1}}}
#declare D =difference {
    box {<-1, 0, -1>,<1, 0.6, 1>}
    box {<-2, 0, 0>,<2, 1, 1> rotate x*-45 translate -z}
}
union {
    cylinder {<-0.7, -2, 0.7>,<-0.7, 2, 0.7>,0.3 pigment {Clear}}
    box {<-2, 0, 0>,<2, 1, 1> rotate x*-45 translate -z translate y*0.6
pigment {Clear}}
    difference {
        cylinder {<0.7, 0.3,-0.7>,<-0.7, 0.3,-0.7>,0.1}
        intersection {
            union {
                cylinder {<0.7, -3, -0.7>,<0.7, 1, -0.7>,0.3}
                cylinder {<-0.7, -3, 0.7>,<-0.7, 1, 0.7>,0.3}
            }
            union {
                object {D translate y*-0.001}
                object {D translate y*0.001}
            }
        }
        translate y*0.6
    }
    sphere {<0, 0.3, -0.4>, 0.35}
    sphere {<-0.4, 0.3, 0.4>, 0.35}
    texture {pigment {Yellow}}
    translate y*5
}

G.


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