Am 06.11.2017 um 00:09 schrieb clipka:

>> So , why must I add a small offset in the camera setting to get the expected
>> result instead of dark slopes for the pyramid ?
> 
> I have no idea... yet. All I can say is that William is on the right
> track, in that POV-Ray apparently fails to find intersections of the
> camera ray with the prism's sides for no obvious reason. Presumably this
> happens whenever the ray is perpendicular to the "base" plane of the prism.
> 
> Might be a misplaced bailout when the ray is parallel to the prism's
> sides, which would be ok for standard prisms but out of place for
> tapered prisms.

... and that's /exactly/ what's happening. While tapered prisms use
their own dedicated code path for intersection testing, it appears to
have been created using copy-and-paste - with adaptations, obviously,
but there's indeed an "is it parallel to all sides?" bailout test that
someone forgot to strip from the tapered prisms code path.

Preparing a fix.

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