Difference between revisions of "Fixing nadir parallax errors"

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(note on image loaction)
(fisheye nadir doesn't really work, use rectilinear instead)
 
(2 intermediate revisions by 2 users not shown)
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[[Image:npx-rectilinear-extracted.jpg]]
 
[[Image:npx-rectilinear-extracted.jpg]]
  
These can then be stitched together into a single [[nadir]] image with minimal errors,
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These can then be stitched together into a single [[rectilinear Projection]] image of the [[nadir]] with minimal errors.
in this case I chose a fisheye projection, though a rectilinear or equirectangular
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Effectively this is ''plan view'' of the ground surface:
projection would work just as well:
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[[Image:npx-corrected-nadir.jpg]]
 
[[Image:npx-corrected-nadir.jpg]]
  
This image can then be reinserted into the original panorama project as another
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This ''plan'' image can then be reinserted into the original panorama project as if it was another
source photo with a different lens and stitched as normal.  Here is the result as a
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source photo with a different lens, and then stitched as normal by optimising [[roll]], [[pitch]], [[yaw]], [[Field of View]] and ''d & e'' lens correction parameters.  Here is the result as a
[[QTVR]], the buildings in the distance are a bit wobbly, but this could have been
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[[QTVR]]:
corrected with [[vertical control points]]:
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<pano file="npx-corrected.mov" width="600" height="450" scale="tofit" controller="true" cache="true" />
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<pano file="Npx-corrected.mov" width="600" height="450" scale="tofit" controller="true" cache="true" />
  
 
This scene is of the Abu Dhabi corniche, 30th November 2006.  The buildings are decorated
 
This scene is of the Abu Dhabi corniche, 30th November 2006.  The buildings are decorated
 
in preparation for UAE national day.
 
in preparation for UAE national day.
  
[[Category:Tutorial]][[Category:Tutorial:Specialised]]
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[[Category:Tutorial:Specialised]]

Latest revision as of 18:07, 21 March 2007

Here is a set of source photos for a spherical panorama:

Npx-uncorrected-originals.jpg

They were taken using a one second exposure without a tripod, the camera was stabilised by jamming it against the sides of a palm tree. This means that they don't stitch easily because of the large (approximately 60cm) parallax error:

Npx-uncorrected-equirectangular.jpg

Particularly, the nadir doesn't work at all. This is an extreme version of the usual problems caused by failing to rotate the camera around the No-parallax point:

Npx-uncorrected-nadir.jpg

However the nadir can be stitched by taking advantage of another technique generally used for stitching a linear panorama. The way this works is that if you assume the ground forms a plane just like a mural on a wall; a series of rectilinear Projection images taken from different locations can be assembled by optimising roll, pitch & yaw, Field of View and d & e lens correction parameters separately for each image.

So the first step is to create a series of defished rectilinear images from the fisheye Projection originals. You can do this in any of the GUI front-ends, but you do need to calibrate your lens first:

Npx-rectilinear-extracted.jpg

These can then be stitched together into a single rectilinear Projection image of the nadir with minimal errors. Effectively this is plan view of the ground surface:

Npx-corrected-nadir.jpg

This plan image can then be reinserted into the original panorama project as if it was another source photo with a different lens, and then stitched as normal by optimising roll, pitch, yaw, Field of View and d & e lens correction parameters. Here is the result as a QTVR:

This scene is of the Abu Dhabi corniche, 30th November 2006. The buildings are decorated in preparation for UAE national day.