After a (diligent)use of slic3r, I've some perplexity about command-line functionality and slic3r configuration file documentation:
1. The slic3r.pl command-line parameter `--rotate` accepts only an angle in degrees, but the UI permits to choose around which axe to rotate (at least to correct sometimes from the STL the best orientation to consider for print)
CuraEngine for comparison, accepts from command line a matrix [-m 3x3matrix] (which in addition to a full control on rotation, even allows elliptical scale)
I prefer the command line because I run slic3r in a remote raspberry PI and ssh X11 forwarding `slic3r.pl --gui` on such device run too slow; but without the UI I don't see how to rotate and print for example upside-down, am I missing something?
2. Newer version 1.2.9+ of slic3r has a more complex syntax of the configuration option bed_shape, what is the meaning of the 4 couple of values, where user are supposed to find it documented?
3. Why the configuration option --print-center works only by command line, but print_center configuration option is ignored if specified in the .ini configuration file (loaded with --load) ?
I expect those issues can be addressed by the developers only, I might contact them by e-mail if this post doesn't reach them.