Roman Reiner <lim### [at] gmxde> wrote:
> the simpliest solution is always to use

> right x*(image_width/image_height)

  I would recommend against *always* using that. There are several reasons:

  If you use that, the image will be cropped or new parts of the scene
will become visible if the user renders the image with a different aspect
ratio than the author.
  Both of these things can be bad, depending on the scene. If the image
gets cropped, compositionally important parts of the image may be left
out of the image, and the user might not even notice. The original
composition might be severely damaged by this.
  Also the other way around: If parts of the scene which originally were
out of view become visible, it may also destroy compositionality. It may
be that the author didn't bother modeling the rest of the scene which is
outside of view, and if it suddenly comes into view it may look awkard and
bad. And once again, the user might not even notice this (but just think
that the author was incompetent).

  Secondly, if you use 'angle', there's a rather peculiar and often
unwanted behaviour: Simply changing the aspect ratio with 'right' will
always crop or add new scener *vertically*. IOW the image will be cropped
or enlarged in the upper and lower sides of the image. Always.
  More often than not, this is unwanted. Most scenes are rather panoramic
in nature, meaning that they work well if they are enlarged *horizontally*
but not so well if they are enlarged vertically.
  So if you render an image with a larger viewing area, new scenery will
be seen only in the upper and lower part of the image, not on the sides.
  More importantly, if you want to render a "widescreen" version of the
image, what will happen is that the image will just get cropped in the
upper and lower sides, it will not be expanded on the left and right.
This is usually not what one wants.

  If you use a *fixed* aspect ratio with your scene, however, the
compositionality of the scene will never be modified. The only thing
which will happen if the user tries to render with the wrong aspect
ratio is that the image will get deformed. There's a much higher
chance that the user will see that there's something wrong with his
rendering settings this way than when the camera aspect ratio is
calculated automatically.

-- 
                                                          - Warp

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