In this topic, I'll explain how I have created "little planet" panoramas such as this one posted on the forum
There are actually 2 methods : the real one, and a quick-and-dirty workaround.
Genuine little planet panorama
So for the real thing, it's quite easy. What you'll need is a 360x180 panorama. So you may want to refer to this generic panorama tutorial http://themobilephotographyblog.com/mobile-photography-techniques/how-to-create-a-great-panorama-tutorial/
to understand how to create a panorama.
You'll need to cover 360° (all around yourself/your tripod) AND 180° (from zenith to the ground).
Once stitched, you'll get a standard panorama. For instance (not hosted on the forum because too big) :http://sdrv.ms/1gff3gg
It's not an issue if you don't have a perfect 360x180. You should have 360, but between 170 and 180 of vertical angle is good enough.
Now it will depend on the software you're using to stitch the panorama.
A) If it's NOT Hugin nor Autopanogiga, you won't have a "little planet" projection. Too bad. Use a "stereographic" or "equirectangular" projection and stitch it. Then import it in Hugin (hugin.sf.net), yes, a single image, you'll be asked for the lens specs, set equirectangular lens and HFOV to 360 and click ok. Then skip to C)
B) If you're using autopanogiga, you have a little planet projection, go for it, it's straightforward
C) In Hugin, you have to change your projection to stereographicn then rotate (pitch) 90°. Then zoom in or out and you'll see the little planet!
Once rendered, you'll have to fine-tune the little planet. Like using the clone tool (in the GIMP, sorry, I'm a Linux guy) to remove inconsistencies in the sky (where it is stitched), or because you'll have a hole in the your planet. Why? Remember, I said 170+ was enough for vertical angle. Good enough, but this comes with a drawback: the missing part will make a "hole" at the centre of the planet. No need to worry, again some clone tool grooming and that's it.
So applied to the mountain panorama (skydrive link above to the original), this gives:
Now look at it more carefully. You can guess where I was standing turning around myself (no tripod). I've used the clone tool to erase the hole and fill it with "snow"
The poor man's little planet
I don't like this second method, because it's not as beautiful than the previous one. But it's less demanding. You'll have to have a good panorama, where left and right sides can connect properly. You can crop your panorama to do so. Now in the GIMP or Photoshop, you have to modify the size of the image. Let's say you have a 1234x567 image. You have to change the image size (untick "keep proportions" or equivalent") to have a square of 1234x1234. The image will look ugly and stretched, it's normal.
Now rotate that image of 180° (upside down).
Finally, find the "polar coordinates" filter. In Photoshop, it's in Filter/Distort/Polar Coordinates ; in the GIMP, it's the same
Now you have your little planet. But I don't like this method, because everything is radially stretched. Clouds won't be as beautiful as with the stereographic projection, for instance. If you have buildings on the panorama, they'll look more natural with the first method than with the second one.Conclusion
: prefer method one and "invest" in a 360x180 panorama