| 2011-01-22 22:17:57 |
Bruno Postle |
description |
The stages of the existing smart optimisation that happen when you use Align... in the Assistant tab are:
First it optimises just positions, if the final panorama is 360° then it will optimise field of view of the photos in the next step.
It looks at the spread of control points and either optimises just 'b' or 'a,b,c' lens parameters depending on this spread.
If the photos are wider than 60° then d,e will be optimised too.
It does some checks with the result of this second step, if the v,a,b,c,d,e parameters are not credible then it backs out and optimises the project again but with less parameters.
(from SmartOptimise::smartOptimize in src/hugin_base/algorithms/optimizer/PTOptimizer.cpp)
Looking at this code, some of the default thresholds and heuristics could be better:
I think it is safe to optimise field of view if the panorama is greater than about 150° (and if the panorama is not a single stack).
The a,b,c thresholds are much too high.
High a,b,c values can be an indication that the lens type is incorrect, perhaps at this point it would be useful to run another optimisation with fisheye/rectilinear and see which gives the best results.
The straighten function is run but this doesn't work unless there is some horizontal spread of photos (i.e. a vertical panorama fails) see Bug #679282 (sf-2851956)
a,b,c,d,e should never be optimised when the initial alignment indicates that we have a single stack (i.e. the assistant is currently broken with all single stack projects).
The d,e threshold should be a proportion of the photo width rather than a pixel value.
Photometric optimisation is always performed, but this is almost always a mess unless there is a good geometrical alignment. So if the alignment is bad, then photometric optimisation should be skipped. |
The stages of the existing smart optimisation that happen when you use Align... in the Assistant tab are:
First it optimises just positions, if the final panorama is 360° then it will optimise field of view of the photos in the next step.
It looks at the spread of control points and either optimises just 'b' or 'a,b,c' lens parameters depending on this spread.
If the photos are wider than 60° then d,e will be optimised too.
It does some checks with the result of this second step, if the v,a,b,c,d,e parameters are not credible then it backs out and optimises the project again but with less parameters.
(from SmartOptimise::smartOptimize in src/hugin_base/algorithms/optimizer/PTOptimizer.cpp)
Looking at this code, some of the default thresholds and heuristics could be better:
I think it is safe to optimise field of view if the panorama is greater than about 150° (and if the panorama is not a single stack).
The a,b,c thresholds are much too high.
High a,b,c values can be an indication that the lens type is incorrect, perhaps at this point it would be useful to run another optimisation with fisheye/rectilinear and see which gives the best results.
The straighten function is run but this doesn't work unless there is some horizontal spread of photos (i.e. a vertical panorama fails) see Bug #679282 (sf-2851956)
a,b,c,d,e should never be optimised when the initial alignment indicates that we have a single stack (i.e. the assistant is currently broken with all single stack projects).
The d,e threshold should be a proportion of the photo width rather than a pixel value.
Photometric optimisation is always performed, but this is almost always a mess unless there is a good geometrical alignment. So if the alignment is bad, then photometric optimisation should be skipped.
Photometric alignment needs significant vignetting and/or bracketed exposures to be able to calculate the camera response curve, 'bad' response curves result in 'banding' or 'posterisation' artefacts. The Assistant tab could be refined to back-out of photometric alignment if the vignetting turns out to be low or there is no EV variation. |
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