Am 05.11.2017 um 13:00 schrieb Warren:

> After a quick research, I found this post:
> http://news.povray.org/povray.beta-test/thread/%3C3cd1c5ac%40news.povray.org%3E/
> 
> I have a hard time understanding why this is not a bug (the explanation of "
> Thorsten Froehlich" especially); my camera isn't 'in' the conic_sweep object.

No surprise you can't make heads or tails of the thread - none of the
replies there have anything to do with the problem you're facing.

(As for the replies by Warp and Rune, I'm not exactly sure what Warp
meant back then; fact is, orthographic camera rays do start in the plane
passing through the camera location and aligned with the effective (*)
`up` and `right` vectors.)

(* Note that when `look_at` is specified, any explicit `up` and `right`
vectors are only relevant for aspect ratio and handedness issues, and
the effective direction of those vectors is instead computed from
`location`, `look_at` and `sky`.)


> 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.

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