L. Zelnik-Manor, G. Peters, P. Perona
Images taken by a rotating camera can be registered and blended on the sphere using available software tools (e.g. Autostitch). To obtain a single flat image one has to project the sphere onto the plane. This projection is bound to introduce some perceptual distortions in the resulting panorama.
The two most common projections used for panoramas are perspective and geographic. Many other projections have been suggested by cartographers but all introduce some perceptual distortions.
|Cubes under perspective projection at wide field of view||An overlay of rectified face images taken by a rotating camera|
A conformal cylindrical projection. The horizontal axis is linearly proportional to the horizontal angle. The vertical axis is set to maintain conformality, i.e., local aspect proportions are maintained and small circles in the scene are projected onto circles in the panorama. This is different from the geographic projection which turns circles into ellipses.
|Geographic: The shaft of the Pantheon ceiling is squished into an ellipse||Mercator: The shaft circularity is maintained|
Comparison of the three approaches:
|Perspective: stretches too much||Geographic: bends horizontal scene lines||Mercator: bends horizontal scene lines|
Suggested Alternative: Multi-Plane Perspective Projection
Project the sphere onto multiple planes which are then unfolded into a single flat image. The projection onto each plane is perspective. The large discontinuities between the planes can be hidden where the world already has a discontinuity.
|Geographic||Our result: Multi-Plane Perspective|
Preserving Foreground Objects
Foreground (nearby, viewed at large angle) objects look distorted under perspective projection. To correct for that we allow multiple view points to reside in the same panorama. This is done by using a different projection for different objects in the scene.
|Standard Perspective: Heads at wide angles look distorted||Our Results: Multi-View Perspective
The heads look good all over the panorama
For details on how we do that please refer to our paper.