[ptx] Using nona before autopano-sift for ultra wide-angle lenses

[Sebastien Perez-Duarte]

Hi all

I have a very wide angle lens (Canon EF-S 10-22mm) I use for
equirectangular panoramas. One big problem I have is that
autopano-sift is not very efficient with the corner of the images,
where the deformations are greatest. The control points found are all
in a small central area, hence stitching is not always good, and I
have to manually add control points in the corners... and then, why do
I use autopano-sift ?

I would lilke your feedback and your help with a new workflow that (I
think) would help autopano-sift.

1) I know how the images are shot, give or take a few degrees: one row
at 30° down, one row at 30° up, one above and one below. I could then
use nona or PTStitcher to transform these images in an equirectangular
projection (-30° and +30°), using the simplest parameters.

2) autopano-sift could then be used in these transformed images, where
the deformations apparent in the original images have been erased for
the overlapping images.

3) Some process (hopefully not very hard to program out of the PT
tools) then projects the control points found on the transformed
images back to the original rectilinear coordinates.

4) hugin is run as usual with these control points and the original
images. The rest of the usual workflow follows.

What do you think ? do you have an idea how the point 3) could be done ?

Thanks in advance

S