Introduction

This is a VR image of the hall of the Eindhoven railway station. You can rotate freely in it and look around.

This is the original 360 degree panorama from which the VR image was derived. It is an equirectangular 360x180 degree panorama, containing the full sphere around the camera.

The 360 x 180 degree panorama is obtained from 20 different images. Six horizontal ones, six upwards pointing and 6 downwards pointing, as well as two pointing to the floor. ( Actually, for each direction 3 images were shot, with different lighting, as the contrast in the total image is beyond that of the camera. ) These 20 images do have overlap and together form the full sphere around the camera. The 6 downwards pointing ones do contain the tripod, therefore, two additional images of the floor below the tripod were taken, containing the feet of the photographer. The 20 overlapping images were stitched together to obtain the full sphere around the camera. The tripod, feet, and other unwanted parts, like half people on the edge of image, have been masked out.

The result is a spherical image, that cannot be undistorted represented on a flat surface. This is a view of half of the sphere.

To flatten the sphere, and project it onto a plane, it is first cut open. Here, this is done on the top. There are two choices to be made here: the angle of the direction where the cut is being made, and the size of the circular cut, also represented by an angle.

After the cut, the remaining part of the sphere is flattened onto the plane oppposite to it, in this case, the floor. This requires a lot of stretching, like it was a rubber balloon. The stretching results in heavy distortions, as you can see e.g. on the ceiling. That ceiling was the part that surround the cut, and now is being stretched to the outside of the projection, while the floor is in the center.