Ron Parker wrote:
>Panoramic cameras have a fixed angle because that's the way they were made.
>They always render a hemisphere.  I'm not sure how you can say the aspect
>ratio is wrong; it's just a matter of understanding that "aspect ratio"
>is meaningless when your pixels are measured in degrees instead of inches,
>because the distance in inches across the center of the image will always
>be infinitely larger than the distance in inches across the top of the image.
>
>"panoramic" is like half of a Mercator projection, but without the correction
>factor that keeps Greenland from being "squished" vertically.
>
>I think you'll find that the effects you're looking for are easier to
>achieve with the ultra_wide_angle camera type rather than the panoramic.
>

I must confess, I was a bit fuzzy with the term "panoramic" in my
recent posts. I judged the images povray renders by comparision with real
world (photographic) panoraic cameras. Those cameras often have a fixed
angle, e.g. 140deg, 180deg, 360deg. But there is no reasonable limitation
in the formula used to create the image that would dictate a fixed angle of
180deg.
(Of course, we can't go byond 180deg in vertical direction).

With "cylinder 1" camera (perspective projection in vertical, panoramic
in horizontal direction) you can achieve similar results to photograpic
cameras. But sometimes the Mercator projection would yield better looking
results, if there was a way to better controll the working of POV-Ray's
panoramic camera. As a user, I see no reason why I should not render a
image covering 240deg horizontal and 60deg vertical angle.

With regard to the aspect ratio, you are right if we relate the "aspect
ratio" to image angle covered by a given pixel. But on the other hand,
the image is created by projection on a unit cylinder. We can wrap the
image off this cylinder to a flat rectangle, and the aspect ratio of
this rectangle can be judged.

Thus, in my first post, I proposed to modify the handling of the angle
parameter in a way to ensure, the final image wraped off the cylinder
sticks to the aspect ratio set by "up" and "right" vector.

Hermann Vosseler

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