Margus Ramst wrote:
> 
> Well. You asked for it, you are gonna get it...
> 

To correct a stupid mistake:

As I said, with the standard perspective, the scene is mapped to a rectangle.
However, I was wrong about the distribution of samples.
Camera rays hit the rectangle at *constant intervals*; in order for this to
happen, the angle between consecutive rays has to decrease towards the image
edges. Thus, in model space, rays are distributed more densely as they move away
from the camera axis. *This* is what causes features to be stretched towards the
edges.
Note also that since camera rays hit the mapping rectangle at constant
intervals, they also hit at constant intervals all surfaces coplanar with the
mapping rectangle. This means that, given two points parallel to the viewing
plane, the distance between these points remains constant regardless of their
position in screen space. The distance is not distorted towards the image edges.
However, for all points not parallel with the viewing plane, distortion does
occur.

Margus

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