How to use the sparse depth?

[Pattern6]

Thank you for your outstanding contribution！
I want to know how the Color-dominant Branch is combined with the point cloud and sent to the network. Does the radar point cloud only take effective points, and does the color image also take the same effective points as the point cloud? How can we get a dense depth map in this way?
This question has been bothering me. I hope you can answer it for me. Thank you again！