code: public float getFarPlane() {
          if (farPlane == -1) {
              // Recalculate the distance if the cache is invalid
              final Vector3f farPos = vertices[1].add(vertices[3]).add(vertices[5]).add(vertices[7]).div(4);
              farPlane = farPos.sub(position).length();
          }
          return farPlane;
      }
docs: Returns the far plane distance of the frustum.
  
  @return The far plane