I've finally managed to get something useful put together. The initial challange was to export camera movement in a format that could be read and interpreted by Terragen 2. Terragen 2 can load a file format that is known as "chan" (channel?) file. It's a text file and contains several columns of numerical data (frame number, x/y/z, rotate-x/-y/-z, focal length, aspect ratio and horizontal aperture width).
The major problem involved was the data conversion to suit Terragen's expected format. X-Rotate is the up/down tilt of the camera (i.e. +/- 90°), Y-Rotate is the rotation around the Y-axis (any angle) and Z-Rotate is +/-180° left/right camera tilt. The actual angles in Terragen can have any value though since the motion blur will support multiple turns. This is why right now Terragen will have a problem when rendering the frame preceding a Y-angle change from negative to positive. Motion blur just can't handle an almost 360° movement in one frame...
I used several tutorial fragments and the A:M SDK to implement my own exporter plugin. You can find it attached here, unzip and copy into the "htx" subdirectory of A:M. Since I consider this a beta version there might be "side effects" involved. I recommend backing up any project (and related) files before using it! Uninstall by deleting the ".htx" file.
TODO: Find a (usable) way to convert the single, current value that A:M uses for the rotation to a smooth increasing/decreasing angle...
See also: Original Posting
If everything works, the plugin will add a menu entry "Channel file" to the "Plugins"-"Export" menu of camera shortcuts.
Click to view attachment