In article <3caf823a@news.povray.org> , "Rune" <run### [at] mobilixnetdk>
wrote:

> Right, then one coordinate system is reversed vertically compared to the
> other. Why do you say it isn't reversed when obviously everyone can see that
> it is indeed reversed, no matter what you choose to call it?

It isn't reversed. It is in exactly in the same coordinate system as in all
other images!

>> When generating the image the origin and coordiante
>> system of an image is used.  This means that the
>> upper left is (0,0) and the lower right of the image
>> generated is function value (1,1).
>
> Yet, strangely, when using an image map the upper left corner is at (0,1)
> and the lower right corner is at (1,0). This is because POV-Ray takes care
> of the correction for the user.
>
> Why can't POV-Ray correct the alignment for the user when using the function
> image type, so that the user won't see any hint of reversed coordinates?

It is correct just like for all other image map types.  As I pointed out, try
to substitute the function image by a plain image map.  You will notice that
the origin of the image is of course still at (0,0) in image coordinates,
which equals (0,1,0) in POV-Ray coordinates.  The function is also at exactly
this place, (0,0) in image coordinates and (0,1,0) in POV-Ray coordinates.

So you generate an image using a function inside the image coordinate system,
which goes from (0,0) to (1,1) where (0,0) is defined as the upper left and
(1,1) as the lower right.  The (0,0) is then mapped to (0,1,0) and the (1,1)
is mapped to (1,0,0) like for all other image formats.


    Thorsten


____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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