Cube Map to Equirectangular (LatLong Map)
Now and then you need to touch up matte paintings or sky domes that have been stitched from photos and thus are in a panoramic format like the equirectangular – also called latlong – format.
Let's remove the hole in the floor. Example panorama from HDRLabs.com's sIBL archive.
In these cases a useful workflow involves rendering an undistorted view using a camera with an angle of view of 90 degrees and a square film back. If you did this 6 times along each axis it would be called a cube map, but usually you only need one face of the cube for retouching and it doesn’t have to face exactly in the same direction as an axis.
The advantage of these cube maps is that straight lines stay straight, which means you can easily use Photoshop’s vanishing point tool on walls and floors. The problem is the inverse transformation, that takes you back to a distorted, equirectangular panorama. Nuke has a nice tool called “SphericalTransform”, but Fusion users had to rely on 3rd party plugins or software like Hugin or HDR Shop.
The modified cube map tile is transformed back into a latlong map.
Well, not anymore. This Fuse, called CubeToLatLong, will do the inverse transformation for you. The formulas I’ve used can be found here.
Download CubeToLatLong_v1_0.Fuse or read more about it on Vfxpedia.
