On Wed, 11 Feb 2004 08:06:22 -0500, Christopher James Huff 
<cja### [at] earthlinknet> wrote:

> In article <opr27akwh2p4ukzs@news.povray.org>,
>  Phil Cook <phi### [at] nospamdeckingdealscouk> 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.
>

Sorry my bad I don't use planes that often and was confusing my terms; 
again sorry, of course plane{y,y} should have been plane{y,1} etc. Odd 
that when I code I don't tend to get it wrong but do when I try to post it 
in a newsgroup for the whole world to see :)

--
Phil


-- 
All thoughts and comments are my own unless otherwise stated and I am 
happy to be proven wrong.

Post a reply to this message