Projectiontype exif/xmp tags missing when not equirectangular

[ajp_anton]

When setting the projection to equirectangular, the resulting panorama will get further exif (or xmp) tags giving more information of the projection, that apparently some image hosting websites use to show these in a 3d view. However, this feature is completely missing when the projection is something other than equirectangular.

Screenshot shows the ends of the output from exiftool of two panoramas of similar size but different projections.

[tmodes (tmodes)]

According to the spec of GPano https://developers.google.com/streetview/spherical-metadata currently only equirectangular is supported for ProjectionType.
Also the values for FullPano*Pixels and CroppedArea*Pixels are only defined for a equirectangular projection. There are no conventions for these tags when using another projection and especially for partially panos in these projection.
So Hugin write the GPano tags only for equirectangular panos.

[ajp_anton (ajpanton)]

Well, I would disagree with only living in Google's world and only do what Google supports. Some other software might support something else, or if not, then maybe because everyone else just follows Google and somebody has to make the first move.

However if the whole spec is Google's, then I can understand this choice, and the lack of a definition for the pixel values.

[tmodes (tmodes)]

The namespace of these tags is http://ns.google.com/photos/1.0/panorama/
So we have to follow these guidelines.
The mentioned site with the spec is automatic translated by Google, but some information are missing in the translated page.
I have seen that the English version contains also some information about the cylindrical projection (but there are some discrepancy, e.g. the FullPanoHeightPixels is infinity, but this is a required tag of type integer)
I added this case to default branch.

Otherwise you can write the information to other tags. In the preferences, tab stitching (2) you can create an Exiftool argfile and write the information to tags you want.