- solidify/face.h (fx_to_angle, fy_to_angle, fx_from_angle, fy_from_angle): helper functions to get/set the z0 plane inclination - solidify/povray.c (povray_face), solidify/project.c (read_face_data, save_face_data): use helper functions to get/set z0 plane - solidify/project.c (read_face_data, save_face_data): don't negate fx