On Sep 25, 3:02 am, Tduell <[email protected]> wrote: > Hullo All, > > I have uploaded a new tutorial [0] to the website which explains the > basics of mosiac mode in stitching a mural.
Nice one! I have a point though where I think your discussion of mosaic mode isn't entirely correct: As far as I understand it, those parallactic errors that apply to a flat surface when photographed from different positions can entirely be corrected by the x-y-z optimization. You state that "The aim is to have minimal variation in Z, as variation in Z will cause parallax errors." Judging from my experience you may have to change that statement. You can vary the distance from the flat object, but if you also optimize for Z, the error will be corrected. This is quite easy to verfiy: Put a poster or such flat on the floor and photograph first the whole thing and then something like a 30% section of it (not by zooming in, but by actually going closer - zooming in would not produce a difference in parallax!). Find control points, then optimize only for X,Y, Z, roll, pitch and yaw of the second image. I tried that, and the small section fitted perfectly onto the bigger image. Do that with a well-calibrated lens - If it isn't well-calibrated, optimize a,b and c only in a second step. Only if the object is not flat, the x-y-z optimization cannot correct those parallactic errors. But then you can't correct them at all, only work around them. This is why Yuval Levy in his tutorial seeks for flat areas in the image where he can put the seams - overlap in flat areas [and let me add, they don't only have to be flat but must be in the intended image plane] will not be encumbered by the unavoidable parallactic errors, but if you don't have 'bulges' or 'holes' where the seam is, the parallactic differences will not be obvious, even though they are still there and may throw your CPG off balance. Please correct me if I'm wrong, but I'm pretty certain I'm not, and this opens up quite exciting possibilities, since you don't have to stay within the same distance from the object, which gives you additional degrees of freedom! with regards KFJ -- 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
