Cubefaces size for fullscreen panorama
Full Screen 360 degree Virtual Panoramas - weekly feature presented by Hans Nyberg
panoramas.dk is hosted by: VRWAY
Optimal cubeface size from Equirectangular panorama

When calculating the size of the cubefaces from an Equirectangular panorama CubicConverter uses a Pi calculation which from a size of for example 8600x4300 panorama will give you cubefaces of 2736x2736. This is supposed to give you the optimal resolution.

However as you will see you can reduce this size with a large reduction in download and still get a quality which is difficult to separate from each other.

The main idea for the reduction is the fact that the resolution of almost all digital cameras is in fact only 70% of the resolution in the specifications.

This was explained by Ken Turkowski many years ago and is called the 70% rule.

“Ken explained about optimizing the resolution of panoramas with his 70% rule. There is negligible loss of image quality when shrunk by 70%. This reduced the file size by half! This is because the Bayer pattern found on most digital camera sensors interpolates up to 30% of the image resolution.”

The panorama above is a crop of an 8600x4300 105.8mb Equirectangular panorama. It is the max resolution from 4 images Canon 5D + Tokina 10-17 at 12mm. 2 movies was made in CubicConverter from this panorama. One with the theoretical 2736x2736 resolution which is the default for CubicConverter. The other was made at 70% resolution 1904x1904 pixels. Compression was the same for both 50%

These are the uncompressed sizes: Original size 8600x4300 105,8mb - 2736x2736 = 21,4x6= 128,4 mb - 1904 = 10,4x6= 62,4 mb

Both panoramas are zoomed in at the full resolution of the 8600x4300. Scroll the pano above to find the same area.

You can also compare the quality with the output from Pano2VR

Click to load 2736 version Pano2VR

Click to load 1904 version CubicConverter

Note that the memory usage of the 1904 version is less than half of the 2736.

The download size is reduced from 4.2 mb to 2,2 mb

The panorama is from a Virtual Tour of the Danish Agricultural Museum