Stitching fisheye photos: a tip for the new term

From Autopano

Introduction

In some cases, stitching may require more time to obtain a satisfying result: It is sometimes necessary to remove bad links and add new control points, re-optimize the panorama or recheck the links, etc.
Here is a tip, then, that allows you to save an enormous amount of time when carrying out difficult assemblies, especially when working with full spherical panoramas shot with a fisheye lens.

In presenting this tip, we are going to use shots that contain 8 fisheye photos, shot in 6 + Z + N mode (6 horizontal photos, one photo on the Zenith and one photo on the Nadir).
In this type of shot, the mesh should look like this:

Image 1 is linked to 2, 6 (puisque 360°) then to 7 and 8.
Image 2 is linked to images 1, 3, 7 and 8
Image 3 is linked to images 2, 4, 7 and 8
Image 4 is linked to images 3, 5, 7 and 8
Image 5 is linked to images 4, 6, 7 and 8
Image 6 is linked to images 5, 1, 7 and 8
Image 7 is linked to images 1, 2, 3, 4, 5, and 6
Image 8 is linked to images 1, 2, 3, 4, 5, and 6

Based on this principle, the idea is to let Autopano calculate all the links, remove false links and re-optmize the panorama. 3 quick steps to obtain a perfect result!

Example 1 : Rubiks Cube

The shot

Step 1

After importing the photos in Autopano (and checking the shooting information), open the Group Settings and select the Optimization tab.
Open the avanced settings and uncheck all options keeping only the Local Approach option checked:

Confirm (OK) and launch the detection:

The RMS of the stitching is very poor (62.29) but this is not important for the moment.

Step 2

Open the Panorama editor, then the Control Points editor to check the links mesh:

It is clear that the mesh doesn't correspond at all to the ideal mesh shown above.
Autopano has calculated all the links without removing those that may be considered bad.
Such settings used for the group allow to retain all the links and all the control points.
Now you only need to remove the bad links using the links list from the control points editor, to obtain a mesh similar to the ideal one:

Here is the list before cleaning. One can see the list of wrong links in the upper section (e.g. image 1 linked to images 3, 4 and 5):

After cleaning (removal of wrong links), the list looks like this (identical to the ideal grid):

L'image 1 is linked to 2, 6 (because 360°) then to 7 and 8.
L'image 2 is linked to images 1, 3, 7 and 8
L'image 3 is linked to images 2, 4, 7 and 8
L'image 4 is linked to images 3, 5, 7 and 8
L'image 5 is linked to images 4, 6, 7 and 8
L'image 6 is linked to images 5, 1, 7 and 8
L'image 7 is linked to images 1, 2, 3, 4, 5, and 6
L'image 8 is linked to images 1, 2, 3, 4, 5, and 6

Step 3

Now that the mesh is clean, it is necessary to re-optimize the panorama. Before carrying out this operation, a slight modification of the optimization settings is required.
Open the Control Points editor settings in the Optimization tab and select the Fisheye profile:

Confrim (OK), then run a complete optimization of the panorama (using the icon):

The stitching is perfect (RMS of 3.26). The last thing to be done is to export the panorama!

Example 2 : Chapel

The shot

In this example, the shot does not contain the Nadir.

Step 1

As in example 1, import the photos, check the shooting information and open the Group Settings in the Optimization tab.
Open the avanced settings and uncheck all options keeping only the Local Approach option checked:

Confim (OK) and launch the detection:

The RMS for the stitching is also very poor (62.29) but this is not important.

Step 2

Open the Panorama editor, then the Control Points editor in order to check the mesh:  

As in example 1, the mesh does not match the ideal one.
It is now necessary to remove the bad links using the links list from the control points editor, to obtain a proper mesh:

Here is the list before cleaning containing the wrong links (1 linked to 4, for example): 