Difference between revisions of "Fixing nadir parallax errors"

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m (fixed the Pano-name... Mediawiki always capitalizes the first letter...)
(fisheye nadir doesn't really work, use rectilinear instead)
 
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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" />
 
<pano file="Npx-corrected.mov" width="600" height="450" scale="tofit" controller="true" cache="true" />
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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.