This is a ray-tracing engin written in java (Processsing)
(cpu only single thread)
this is an interative rendrer which allows you to move in the sceen with real time rendring
made with processing : https://processing.org/
more about computer graphics : https://www.gabrielgambetta.com/computer-graphics-from-scratch/
initialy it wont render and will just trace ray and let you move around pressing the r ( small r ) button on your keyboard will start rendring and the mini-map will help you guid yourself.