something error of the Groundtruth file

[tftangming]

I try to use my dataset(color and depth) and groundtruth file (recording the transformation from the camera to the world), but I can not success run the program. And I find the code in file GroundTruthOdometry.cpp
Eigen::Matrix4f M; M << 0, 0, 1, 0, -1, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, 1; currentTsdf = currentTsdf * M.inverse() * delta * M;
I can not understand the meaning of matrix M, Can you give me some suggestion? Ths!