the origin(start point) of raycasting line?

[lukechencqu]

hello: thanks for your great work!

2 questions: (1) I have a question about the definition of the origin of raycasting. in your paper at IV.B, it says for raycasting(x k , P k ), xk is the position of lidar(lidar_link); but in Algorithm 2, it says xk is the position of the robot(base_link); so, what is the real origin of raycasting? in my opinion, the origin should be the sensor's origin, right? or, if the center of robot and the center of a lidar is very small like your quadrotor, the this maybe negaleted.

(2) if a robot use several sensors to generate pointcloud, for example a lidar and two rgbd, then, my question is how to cover this multi-sensors configuration?