A technique for making "Little planet" (stereographic projection) views.

Designed by Brian Watson, 4th November 2010

Stereographic projections of panoramic views are becoming quite commonplace and can be impressive; despite this, they are not difficult to make. This illustrated tutorial shows how to do it.

Requirements

You will need Photoshop and (usually) a 360x180° panoramic image.

Source Material

Conventionally, Little Planet views use as their source a 360 x 180° panoramic view which is twice as wide as it is high. The reason for this is that the left edge of this type of image will always merge seamlessly with the right edge. If they didn't, the finished result would have an obvious seam.

Non-panoramic source

For me the interesting thing was realising that the main requirement is not for a strictly panoramic image: any shape will do, as long as the left edge will merge with the right edge without leaving an obvious seam running radially from the center of the picture. Interesting and often unexpected results can be obtained using images of this type. I'll illustrate this by using examples of both types of image.

How to do it

Here are two suitable images, a 360x180° degree panoramic image, and a (non-panoramic) picture of a flower against a uniform black background. The flower does not touch either edge of the frame: there MUST be a gap, because the edges will need to merge seamlessly.

360x180 panorama Red-Hot Poker

Make it square

The first step is to make the picture square. In Photoshop, go to Image size (Command-I, PC ctrl-I). Make sure that "Constrain proportions" is DESELECTED, because the proportions are going to be altered.

panorama squared


Note the figure in the Height box: type this into the Width box and press Return.

panorama squared poker squared

Now both examples are square.

Rotate 180°

Now the picture must be rotated 180°: Image > Image rotation > 180°:

panorama squared


panorama squared panorama squared

Polar to rectangular transformation

Apply Polar>Rectangular transformation: Filter > Distort > Polar coordinates... using Rectangular to polar. The zoom level has been adjusted so all of the 'planet' is visible:

panorama squared

Crop and/or rotate to taste, and there is the result!

The finished result:

LP Harbour LP Poker

Attribution

If you use my technique please mention my name and include a reference to my web site: "http://www.brianwatsonphoto.co.uk".



Brian Watson