Ken wrote:
>
>Rohan Bernett wrote:
>>
>> It's nice to see that I'm not the only one with this problem. Could
>> somebody out there tell me whether this glitch can be fixed in the
>> scene, or is it a bug in the lighting and photons in POV-Ray?
>
>A short coded example of the problem would really help.
>
>Ken Tyler
>
I discovered a problem with porting a scene from spotlights to cylinder
lights. What I did was create a screen with a mirror adjacent and
perpendicular to it and aimed two lights at it. One light went direct
and the other reflected off the mirror. It worked exactly as expected
with spotlights, but when I changed the type to cylinder for both
lights the two rays mixed at the center of the screen. (The entire
scene is centered about the origin.) It appears as though the "y" value
of the "point_at" vector is not being handled correctly by POV. I wrote
a simple scene to show this effect and parameterized the relevant
variables. The source code is fully commented and I will send it to
anyone who requests it. The size is 6.24 KB uncompressed, but much of
that is comments.

From my short experiments, I do believe it is a bug in POV-Ray, but
there may be a workaround. I found that sometimes multiplying the "y"
value of the "point_at" declaration by two gave the desired results,
but this did not produce consistent results.

Bob Sorenson

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