This is a little experience: In photography, with 6 or more fisheye photos and a stitching software you can build an image that can be map on a sphere this have many name, one is a QuickTimeVR, you can take this QTVR an map it on a 2 by 1 ratio image ex; 500 L by 250 H, this image is call an Equirectangular image, these images are often used as HDRI light source in 3D software if they are 32 bits. ( This is what I used as light source in my last image on this site call "Still Life Bis" ) With this Equirectangular image you can deform it to obtain a Stereographic Projection, often commonly call LittlePlanet, there many ways to do this but I'll explain how to do it in Bryce. Start with a 2 by 1 document ex; 2000 by 1000 px, create a world, put you camera near the middle of this word, you can rotate the cam on the "y" axe but not on the "X or Z" axes, put the "FOV" of the cam to 180 and instead of the Perspective Projection choose 360 Panoramic Projection and render. You now have an Equirectangular image that you could export as hdr and use it for HDRI or save it as photoshop. There many ways and softwares you can use but this is a simple way to do it: Open your image in photoshop, uncheck "constrain proportion" and resize the wide equal to the hight, in our example 1000 by 1000, you now have a square picture. Flip your image vertically (The sky to the bottom) and apply the Filter/Distort/Polar Coordinates/Rectangular to Polar et voila... A little planet. As usual you comment are always appreciated.