Thomas de Groot <tho### [at] degrootorg> wrote:
> On 25-5-2014 7:58, skippy wrote:
> > Thinking the normals of the planes would be opposing each other (hence y is 1
> > for bottom plane and -1 for top plane). Reference says the distance value is how
> > far along the normal from the origin. So if the normal is going y-negative, I'd
> > need a negative number to bring the plane back 'up' above the camera and light
> > source.
> >
> > But I can't seem to make this idea work. Suggestions?
> >
> >
>
> Your normals are correct, however, you interpret wrongly the distance of
> the plane to the origin. -1 and -7 mean that the planes are positioned
> at -1 and -7 from the origin along the y-axis, irrespective of the
> normal /orientation/.

Thank you for that clarification. After reading the Doc reference I still wasn't
sure.

> If your camera and light are placed at y=0 for
> instance, you can place the planes at:
>
> plane {<0, 1, 0>, -1}
> plane {<0,-1, 0>, 7}
>
> for the effect you are after.
>
> Note that planes have no thickness, so normal orientation is irrelevant
> in your example, except if you want to use a media in between the planes.
>

I understand that planes have no thickness and thought the normal orientation
was important - but wasn't thinking about its effect on texture or media.
After reading the Doc reference paragraph on planes in regards to
"inside/outside" and normal direction, I thought the orientation of the planes'
normals would affect whether the plane was even *visible* (in combination with
camera and light source - of course).
However I've read that section multiple times and still don't quite get it.
Guess I need to take baby steps and hope for enlightenment in the future.

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