The next release increments the file format version and makes it 'c'.
This means that the first line of a new .ac file will change from "AC3Db" to AC3Dc". Older files are still compatible.
Objects now have an (optional) crease angle attribute e.g.
This indicates that if the angles between two joined surfaces is more than 45 degrees, the edges between the surfaces will be drawn with a crease.
Valid crease angles are 0.0 to 180.0 degrees.
Setting a surface to flat-shaded forces it always to be drawn flat.
The default crease-angle in AC3D is currently 45 degrees.
Comments welcome.