On 19 Nov., 08:44, Gnome Nomad <[email protected]> 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 ;-) 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. 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. 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) 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. Kay Kay -- You received this message because you are subscribed to the Google Groups "Hugin and other free panoramic software" group. A list of frequently asked questions is available at: http://wiki.panotools.org/Hugin_FAQ To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/hugin-ptx
