code: private void firePSPEvent(List<Point3d> line) {
          for (int i = 0; i < line.size(); i++) {
              this.grid[(int) line.get(i).x][(int) line.get(i).y][(int) line.get(i).z] = this.grid[(int) line.get(i).x][(int) line
                      .get(i).y][(int) line.get(i).z] + 1;
          }
  
      }
docs: Method which assigns upon a PSP event +1 to these grid points.