Questions about extrinsics in JSON files about persformer_3dlane HOT 1 CLOSED

The camera extrinsic matrix from the JSON file is the standard representation which transforms the coordinates from the camera coordinate system to the vehicle coordinate system. The annotation of lane coordinates from the JSON file are under the camera coordinate system.
But particularly, we will represent the 3D lane coordinates under the ground coordinate system for the model to predict, which is consistent with 3D-LaneNet and Gen-LaneNet, so we add some extra transformation based on the extrinsics in the code.
And the P_g2im matrix in the second picture can finally transform the coordinates from the ground coordinate system to the image pixel coordinate system.
The origin of the ground coordinate system is located on the ground plane, with the y-axis pointing forward, the x-axis pointing right, and the z-axis pointing up. See the following figure from Gen-LaneNet.

from persformer_3dlane.