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Autopano Giga - Panorama Editor - Projections


CONCEPT

This tool lets modify the projection of the current panorama. Many projections are available here, allowing to adjust the global panorama's geometry as well as possible, or even to realize more graphical or abstract images.
Indeed, if some projections are available to recreate real situations to reach specifical applications (planar or spherical projections), other projections are generally for aesthetic purposes only.


PROJECTIONS

Spherical projection icon Spherical or equirectangular projection

Advantages:
Authorizes the assembly of all panoramas.
Disadvantages:
For the direct display (without a viewer) of a panorama on the screen and for feel we need to ensure that the curvature of parallel straight lines on the horizon is still acceptable (there is no rule, you need to be the judge).
When the vertical viewing angle is large, the stretching effect at the top of the image (near the zenith) and at the bottom of the image (near the nadir) varies from unusual to very unusual.


Planar projection icon Planar or rectilinear projection

Advantages:
Good choice if the angle is low, recommended for architectural shots because it is the only mode that does not curve lines that are deemed to be straight lines.
Disadvantages:
Can be used only if the view angle is less than 180 degrees along the diagonal of the image, practice shows that beyond 90 degrees the stretching of the image is already visible along the edges and in the corners.
Beyond 120 degrees, the result is no longer acceptable, because the stretching of the image causes an unpleasant loss of sharpness.


Settings

  • Horizontal squeeze: Allows to squeeze the horizontal field of view to improve distortions on the borders of the panorama.


Icône Projection pannini Pannini projection

The Pannini projection is also called "Recti-Perspective", "Panini" or "Vedutismo".

Advantages:
Keep vertical lines vertically and straigt radial lines. This can give a strong sense of perspective on views whose horizontal field of view is wide and has a single and central vanishing point.
Disadvantages:
Makes curved the straight horizontal lines. Squeeze values can reduce or avoid this curving, at the expense of radial lines which would be more or less folded.


Settings

  • Distance: Lets squeeze the horizontal space of the panorama, to avoid distortions due to the horizontal FOV.
  • Maximum H-FOV:
  • Top squeeze: Allows to squeeze the area upper to the horizontal axis of the vanishing point, to straighten horizontal curves of the top part of the image. Verical lines are not affected with this setting.
  • Bottom squeeze: Allows to squeeze the area lower to the horizontal axis of the vanishing point, to straighten horizontal curves of the bottom part of the image. Verical lines are not affected with this setting.


Cylindrical projection icon Cylindrical projection

Advantages:
Can be used up to 360° (horizontally).
Disadvantages:
The lines parallel to the horizon (curbs, tops of buildings) are still more or less curved.
The vertical angle is limited, it is imperative that it is less than 160 ° but the stretching begins to slightly deform at the top and bottom of the image when it exceeds 45 degrees above or below the skyline.


Mercator projection icon Mercator projection

Advantages:
Can be used up to 360° (horizontally). The effect of stretching up and down the image is attenuated compared to the spherical projection.
Disadvantages:
The lines parallel to the horizon (curbs, tops of buildings) are still more or less curved.
The vertical angle is limited, it is imperative that it is less than 160 ° since the stretching begins to slightly deform at the top and bottom of the image when it exceeds 55 degrees above or below the skyline.


Icône Projection mini-planète Little planet projection

The Stereographic projection (also called fisheye projection) can be used to create a little planet. A right way up panorama lets get a planet effect and a backward panorama (180° rotation) let get a tunnel effect.

Advantages:
Allows to create an original view of a panorama, mainly using equirectangular panoramas (360°x180°).
Disadvantages:
Using this projection with panoramas whose horizontal field of view is less to 330° is neither aesthetic nor usable.
Pixels density on image borders is really much lower than the center.


Settings

  • Squeeze: Lets define the projection zone to reduce loss pixel density, this is equivalent to crop the image without deterioration.


Icône Projection hammer Hammer projection

This projection is pretty similar to a flatenned world map, mainly used in astronomy applications.


Icône Projection orthographique Orthographic projection

This is the view point of a sphere, whose panorama is viewed from afar, mapped to the outside and not inside like most other projections.


Icône Projection mirror ball Mirror ball projection

This projection is the result of a visualization of the whole panorama on a spherical mirror, like looking into a crystal ball.








Technical Support / Autopano Giga Documentation