I am having trouble getting the vertical lines in my pano to look vertical. I'm using the vertical lines tool (VLT) but the documentation does not tell you anything (afaik) about what to do when things don't work as expected.
My pano is a 360x170, missing the nadir and I want a spherical projection. I use the VLT to indicate what should be vertical at four, more-or-less equally spaced intervals and press enter. The result is that some of the verticals are OK but others are not. I keep trying with other choices or more accurate choices for vertical line indications, but I never seem to get a result where everything looks right.
I'd be interested to know why this happens with some panos but not with others. Also, some tips on how best to use the VLT would be appreciated. My "tips" are based on experience viz it seems to best (for a 360, spherical projection) to aim for between three and five VLT lines about half the height of the pano.
However, coming from a mathematical background, my guess is that what is going on here is that the VLT defines constraints that AP attempts to solve. For example, if you only draw one or two lines I find that only some parts of your pano are straightened - this seems consistent with solving an under-constrained system of equations. On the other hand, if you draw five or more lines then some constraints (VLT lines) seem to be ignored - consistent with the problem being over-constrained.
So, I would be interested to know what is going on from a theoretical perspective. In particular, I have notice that the VLT changes the vanishing point (VP). Is it the case that what the VLT is actually doing is determining where the VP is? Is there a theorem that says something like "Three VLT lines are necessary and sufficent to locate the VP"?
Did you set the editor to 360x180° or "use maximal projection space"? In that case you get a full sphere, but having an empty Nadir space - and you gett the verticals straight.