Tough time with mosaic

[jmuc...@gmail.com]

I'm having a rough time trying to make a perspective-corrected mosaic with two photos of a poster in a museum, both taken at sharpish angles.

I manually added a bunch of control points, along with a few h and v lines on each image separately, but can't get them to stitch up. I figure I'm doing something stupidly wrong.

I've put the image and pto with the control points here: https://www.dropbox.com/s/y7k32dh7p0tn725/Archive.zip

Any help much appreciated.

[T. Modes]

jmuc...@gmail.com schrieb am Montag, 22. März 2021 um 00:30:10 UTC+1:

I'm having a rough time trying to make a perspective-corrected mosaic with two photos of a poster in a museum, both taken at sharpish angles. 

Any help much appreciated.

There are 2 problems:

* For scanned images and using horizontal + vertical control points the projection of pano should be rectilinear, not equi.

* There is a very high distortion value in the pto file.

I did the following

* On stitching tab or in fast preview window set panorama projection to rectilinear.

* Now go the photos tab, reset lens parameters in context menu.

* First optimise position (yaw, pitch and roll) only

* Then optimise position and translation

* Go the preview window and adjust field of view and crop.

 

[jmuc...@gmail.com]

On Monday, 22 March 2021 at 13:04:05 UTC-4 T. Modes wrote:

jmuc...@gmail.com schrieb am Montag, 22. März 2021 um 00:30:10 UTC+1:

I'm having a rough time trying to make a perspective-corrected mosaic with two photos of a poster in a museum, both taken at sharpish angles. 

Any help much appreciated.

There are 2 problems:

* For scanned images and using horizontal + vertical control points the projection of pano should be rectilinear, not equi.

* There is a very high distortion value in the pto file.

Thanks for this.

I figured adding the h and v points would help. Is that wrong?

What's the rule (of thumb?) for deciding on the projection?

 

I did the following

* On stitching tab or in fast preview window set panorama projection to rectilinear.

* Now go the photos tab, reset lens parameters in context menu.

* First optimise position (yaw, pitch and roll) only

* Then optimise position and translation

* Go the preview window and adjust field of view and crop.

Thanks. I'll try this.

Same question as above, is there a rule (of thumb?) for deciding which things to optimize first?

 

I would be happy to be pointed to a document with what I think of as fairly basic stuff like this explained. The manual doesn't appear to have been much touched in several years and the tutorials use older versions and, while they often give great tips, don't explain the basic functioning of the app in a systematic way. 

For example, I'd have thought what I'm trying to do is like the mosaic tutorial, but there the optimization is just for translations.

[jmuc...@gmail.com]

I should add that although I apparently didn't save the pto this way, I was using rectilinear for the projection.

[T. Modes]

jmuc...@gmail.com schrieb am Montag, 22. März 2021 um 18:54:42 UTC+1:

I figured adding the h and v points would help. Is that wrong?

What's the rule (of thumb?) for deciding on the projection?

No that's right. When you want straigt horizontal and vertical lines you have the use the rectilinear projection, because this is the only projection which preserves these lines. All other projection create more or less curved horizontal or vertical lines.

(The pto files in the provided archive was set to equirectangular projection - which will make problems. Maybe you have send an other version.)

 

I did the following

* On stitching tab or in fast preview window set panorama projection to rectilinear.

* Now go the photos tab, reset lens parameters in context menu.

* First optimise position (yaw, pitch and roll) only

* Then optimise position and translation

* Go the preview window and adjust field of view and crop.

Thanks. I'll try this.

Same question as above, is there a rule (of thumb?) for deciding which things to optimize first?

The general rule would be: Start with only the basic variables (yaw, pitch, roll) and add the others step for step.

For example, I'd have thought what I'm trying to do is like the mosaic tutorial, but there the optimization is just for translations.

 

It depends on the exact use case, so it is difficult to give an general advice.

[jmuc...@gmail.com]

On Monday, 22 March 2021 at 14:19:04 UTC-4 T. Modes wrote:

The general rule would be: Start with only the basic variables (yaw, pitch, roll) and add the others step for step.

For example, I'd have thought what I'm trying to do is like the mosaic tutorial, but there the optimization is just for translations.

 

It depends on the exact use case, so it is difficult to give an general advice.

OK, but are there general cases? For example, here where I have really oblique angles for the photos, should I optimize ypr before position? Or when I'm pretty much perpendicular to the surface I'm shooting, should I do xyz first?

Finally, I was able to stitch these together without the h and v lines. Then I took the resultant image and straightened it out (fixed the perspective), using h and v. What's the method for doing that all at once?

TIA.