On Sun, 12 Dec 1999 04:48:09 +0100, "Rune" <run### [at] inamecom>
wrote:

>I think it's the other way around.
>The rays *does* hit the rectangle at constant intervals, the horisontal and
>vertical angle between camera rays *doesn't* remains constant. *That* is
>what causes the distortion of distances.

Any projection leading to decreasing the number of dimensions leads to
some kind of distortion. Our eyes distort the image, too, but the
projection is not on a planar surface rather a part of a sphere. Our
brain corrects this and we do not notice it, but other kinds of
distortion are quite obvious to the eye.

>An example: When the camera is perpendicular to a plane with a checker
>pattern, the checker pattern is NOT distorted.

*Only* in the central pixel of the image <grin>. Try rendering the
same but bring the camera very close to the checkered plane and
increase the angle to something very big, say 160. See for yourself :)

>But if you imagined a *sphere* around the camera, *then* the rays would be
>positioned more sparsely towards the sides.

With the spherical projection no distortion would occur provided the
screen was spherical. Some old monitors which are quite bulgy can give
great results at 3D provided that you can guess the curvature and then
convert it to POV units.


Peter Popov
pet### [at] usanet
ICQ: 15002700

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