In real life clouds are not glued to the heavenly dome, but pass in relatively straight lines (forget the meteorology for a sec).This means that fluffy clouds high in the sky will look distorted on a background picture. Except maybe when they hover just above the horizon/mountains/treeline.
Absolutely, but the geometry is already present in the original photo. Our projection should be as linear as possible.
I am not yet convinced that a square is better, but maybe I am missing something. Views?
Well, the distance around zenith is four times the distance to the pole, so a one-by-four ratio is what I also figured would be the best back when I first started to experiment with the rectangular projection.
The reason for choosing a square, is that it leaves me with plenty of headroom at the top.
I have rendered some test images.
One-by-four rectangle.
Field of view: 110
One-by-two rectangle.
Field of view: 110
Square rectangle.
Field of view: 110
And then I have added a sky with mountains:
One-by-four-rectangle.
Image 4096X1024
One-by-two-rectangle.
Image 4096X2048 - sky applied to the lower half. Not adjusted for distortion
Square.
Image 4096X4096 - sky applied to the lower quarter. Not adjusted for distortion.
Any views on what comes out best?
Tent and campfire Sky adjusted slightly for distortion
Cec