Andreas Melcher was kind enough to show me his application. It´s a great online tool where you can calculate all reflections in a room. Paint dimensions of your room, place speaker and listening position, this app will show ray tracing of the room.
This amazing reflection calculator will help you locating traps and diffusers in suitable points, further you can try and see the behavior of the reflections, moving speaker and listening position you will see the best place for your sweet spot with minimal reflections possible.
The application visually shows you the different positions of ray tracing.
“I recommend this app to improve the acoustics of your room”