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In article <opr27akwh2p4ukzs@news.povray.org>,
Phil Cook <phi### [at] nospamdeckingdeals couk> wrote:
> > No. The point_at vector is a location, the plane vector is a direction
> > (the plane normal). Thought the two are the same when the location is <
> > 0, 0, 0>, as in your example.
>
> Errr. If light-source{0 rgb 1 parallel point_at y} then surely if I
> connect a line between location and point_at than a plane perpendicular to
> this would be lying at 0 in the XZ plane ie.
Right. The surface normal direction and the point_at location match up,
because the light location is < 0, 0, 0>. You could use a non-normalized
vector as well, it doesn't matter as long as they point in the same
direction.
> plane {0,y} and not plane{y,y} or even plane{y,-y};
Er, no. It would be "plane {y, 0}". The last two aren't even valid
planes...the POV primitive takes a normal vector and displacement
distance.
> in the same way that light_source{y rgb 1
> parallel point_at <1,1,0>} would produce the equivalent of a plane{0,x} or
> plane{y,x} to be more precise: otherwise the scene I've just produced
> wouldn't work; unless I'm just lucky :)
A location of < 0, 1, 0> (y) and point_at of < 1, 1, 0> would lead to a
direction of < 1, 0, 0>, or x. The equivalent plane would be "plane {x,
0}". Again, "plane {y, x}" isn't even a valid plane.
--
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/
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