see developer blog at https://digitalmediabremen.github.io/PolytopeXIa/
navigate to sketch folder ( i.e ./PolytopeXIa/sketches ) and run shell script convert-java-to-processing.sh with the first argument pointing to the java sketch source file:
./convert-java-to-processing.sh ../src/de/hfkbremen/polytopexia/sketches/LaserBeamLogo.java
note that you might need to manually add libraries in the processing editor ( e.g import teilchen.*; or import.gewebe.*; ( from https://github.com/dennisppaul/gewebe ) ).