What is the depth coord in utils.py

[yuto120521]

I've done some training with SUNRGB and now I'm trying to apply the raw data from the camera as test data. I want to convert the raw data to the data format of SUNRGBD dataset. There is one thing I don't understand. About the coordinate system defined in the SUNRGBD_Calibration class in sunrgbd_data/utils.py. I can't understand what the coordinate axis of the depth coordinate is. I would like to know the difference between the coordinate axes of the depth coordinate and the camera coordinate. thank you.