Am 12.09.21 um 11:47 schrieb Bruno Postle:
PTOptimizer.txt is for PTOptimizer, which is a standalone tool that is
independent of Hugin. The nona.txt file describes the behaviour of the Hugin
stitcher.
Panotools supports both 'C' and 'S' image parameters, they do similar things,
describing the rectangle of interest in the photo, but are not interchangeable.
'C' parameters discard all data outside the rectangle, and then all image
parameters (angle of view, lens distortion) relate to this new image boundary.
This is a model that makes a lot of sense if all your photos are digitised with
a flat-bed scanner - the cropped-out areas are not part of the photo.
'S' parameters set the area outside the rectangle to 'transparent', but the
image parameters still relate to the original image frame. This model makes
more sense with digital cameras where all the pixels have come from the sensor,
just that some of them are not wanted (in Hugin there is a lot of overlap with
the masking functionality, which came much later).
It is not straightforward to convert from a project that uses one method to the
other method, so it makes sense for a GUI tool to support one only (since you
don't need both). This is the original schism between Ptgui and Hugin - Ptgui
uses 'C' and Hugin uses 'S'.
So if you are importing a Ptgui project into Hugin, you need to re-optimise
lens parameters because the C parameters have been silently converted to S.
Thank you, Bruno, for the explanation. I stumbled upon this because I
was working on images done with a Xiaomi Mi Sphere 360 - these images
have two circular fisheye images next to each other, and I wanted to
mask them so that I could use the image twice, once for the left half of
the sphere and once for the right half, with, otherwise, identical lens
parameters. I hoped to use 'C' which would have made the job simple.
With 'S' I could create correct masks, but I had to introduce differing
horizontal shift (d parameter) for the two half-images. So I needed two
separate lenses. I also had to assign a hfov of over 360 degrees (for
the whole image, the (square) half-images have about 193 degrees fov).
All of this made the optimization a bit tricky...
I succeeded in the end, but I was wondering what the 'C' was all about.
Now it's clear. I was also a bit miffed that hugin would silently
consume my PTO with a C field to a PTO with an S field, when the two
have quite different meaning.
Kay
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A list of frequently asked questions is available at:
http://wiki.panotools.org/Hugin_FAQ
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