kfj wrote:
On 19 Nov., 08:44, Gnome Nomad <gnomeno...@gmail.com> wrote:
After trying many times to level a handheld beach pano using horizontal
lines, here's what I did that finally succeeded:
1. Set up horizontal lines from the first frame to each of the other
photos, connecting the left edge point on the horizon to the left edge
point in each case.
2. Set up similar horizontal lines for the right edge points.
3. Optimized everything INCLUDING translation.
Like magic, the horizon straightened itself out.
I think it was the translation that made it work. Optimizing without
translation didn't straighten out the horizon.
I think you probably performed some magic, rather ;-)
Could be, maybe the phase of the moon.
Your method sounds odd to me, even though coercing the translation
parameter into use for a strip panorama might sometimes work, it'll
certainly fail in a 360X180.
I'm not that ambitious. I did a 4x4 interior panorama of a local
cathedral, also handheld, that one aligned quite nicely without any
effort on my part.
Here's what I'd do:
1. pick out an image which is near the center of your pano and shows a
good length of horizon. Set a horizontal line control point on it
picking two horizon points as far apart as possible and only optimize
roll for this single image - you may have to adapt pitch manually to
have the horizon at the right height.
2. start with the leftmost image showing the horizon. Pick two points
on the horizon and create a new line (not horizontal or vertical, just
a line control point.) Carry on by adding two horizon points from each
other image showing the horizon to that same line.
3. Now, with the image chose in 1. as your position anchor, optimize
for position. The horizon should be level because of 1. and 2. should
should bring all the other images in line.
Thanks, I'll have to try that.
If your horizon isn't level enough, you can add more horizontal line
control points - now try and put these with one point on the leftmost
horizon image and one on the rightmost.
Finally, keep in mind that your other CPs will likely be from points
on the beach, and since the pano is handheld, there will be
parallactic errors. Using these CPs will result in your images being
aligned by features on the beach, while your horizon goes awry. Try
and delete as many of these CPs as possible - with the horizon defined
by 1-2-3, you might even get away with one CP per pair (providing your
lens is well-calibrated)
Have never calibrated any of my lenses.
While I'm on the topic I'd like to hint at a technique I sometimes use
when I fix horizons: I've made an image in 2:1 format with a degree
pattern (30X30 degree checkerboard, translates to, like, 30X30 pixel
checkerboard on a 360X180 pixel image) and include this image into the
panorama as being equirectangular with 360 degreed hfov. The grid has
a clearly defined horizon and I can now 'glue' line CPs to this line.
The grid image makes a good anchor, then - and for the stitching I
just switch it off in the preview.
Now that's an interesting idea! Will have to try that out!
--
Gnome Nomad
gnomeno...@gmail.com
wandering the landscape of god
http://www.cafepress.com/otherend/
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