Dear CAESES-users, Here is an easy and essential introduction to Feature Definitions, just check out this video. Feature Definitions are encapsulated command sequences which greatly help to fully customize the software to your needs (e.g. define your own curve types, proprietary import & export routines or any other function with user-defined input and output). This video is also an excellent prerequisite for a better understanding of more complex CAESES geometry models, which usually make extensive use of Feature Definitions in the context of Meta Surfaces Cheers Joerg