# Multiple Rectilinear Panoramas

Prof. Dr. H. Dersch - HFU Furtwangen

## Introduction

Two classical methods for displaying panoramic images with large field-of-view are the cylindrical projection and the connection of several rectilinear images. The cylindrical projection is capable of displaying a full 360° view, but bends and distorts horizontal lines. The rectilinear image is perspectively correct, but can not show more than 180° views, practically 120° rectilinear images look quite unnatural. Connecting several rectilinear views is an old solution in photography, but the joints are distracting and difficult to hide.

PTStitcherNG from version 0.7 offers a mode which allows the user to specify any number and orientation of rectilinear projection screens. The size of each screen is automatically adjusted to fit at the edges with the neighboring screens. Additionally, the edges are rounded with a variable width to avoid sharp bends. Any combination of round (cylinder like, mathematically: splines) and straight projections can be created to display panoramas.

The best way to visualize this method is to create an imaginary projection screen in the actual scene. Light rays pass this screen on their way to the viewer in the center. Unfolding this screen to a flat surface then results in the panoramic image. In this model a cylindrical panorama is represented by a cylinder shaped screen, see the example below.

 Cylindrical projection. Panoramic image starts at the green marker. It resembles the projection onto the cylindrical surface shown in the left image. Note that the market scenery is different in the Satellite image.

A multirectilinear panorama is created by an arbitrary combination of straight rigid and flexible elements, see the second example on this page. Note that this multirectilinear screen need not be a closed surface. The creation of this particular panorama is explained in the step-by-step tutorial section.

 Multiple rectilinear projection. The image resembles the projection onto the screen shown in the satellite image. This screen consists of planes smoothly connected by splines.

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