Bryce 6 has the ability to use Real-World Lighting via HDRI (High Dynamic Range Images) for renders via the new IBL menu inside the Sky Lab. However Bryce 6 comes with only a few HDRI files that you can open in the Sky Lab. (10 when I last counted) so searching for HDR files on the web to get a few more options is a natural tendency of any Bryce-geek like myself!
I soon found out that some .HDR files didn't work and Bryce told me that they had to be in "probe" format. This page confirmed my findings, and I proceeded to get HDRShop and start the process… The image on the left is a Latitude/Longitude Format HDR and will not work in Bryce 6. The 2nd image is the Spherical/Probe/Mirror Ball Format HDR and is the only format that Bryce 6 accepts.
[Note: The link to the HDRShop v1.0 page at the USC Institute for Creative Technologies is no longer working, but I did find that the direct link to the executable to still work. The following link also works but you have to fill in your details before the download will start.]
The tutorial at the USC Institute for Creative Technologies is pretty simple to follow and can be used to convert those HDR. files to a Bryce 6-compatible format.
One of the biggest problem I found was getting a program to view the HDR files. Photoshop apparently can do it, but I don't own Adobe Photoshop, but I did find a freeware viewer called HDRView that does the trick. It is pretty old and primitive but it works!.
At least I can convert existing HDR files into something that Bryce 6.0 can understand…
Another caveat to consider:
Bryce will only accept an .hdr file if it is is **exactly* square pixels dimensions. If your .hdr file doesn’t show up in the list when trying to load in the the Sky Lab, check the dimensions; the height and width must be the same.