Order orientations in source space matrix

I am working with my source space MEG timeseries as matlab variables. I loaded the data using "ResultsMat = in_bst_results(ResultsFile, 1);" so that I get all vertices and time points for this epoch. The source space was constructed using 15002 vertices - because we used unconstrained sources, we have 45006 data points for each time point. In total the epoch matrix (under ResultsMat.ImageGridAmp) is 45006 (15002 vertices * 3 orientations) x 4000 (timepoints).

How are the 3 orientations arranged along the 1st dimension of this matrix. Is it such that the first 3 data points are the three orientations for the first vertex? Or at the first 15002 data points the first orientation among all vertices?


The data is stored as successive columns of the matrix are ordered as: [p1 _x, p1 _y, p1 _z, p2_x, p2_y, p2_z ...].
For the tutorial introduction dataset, with 15002 sources, the gain matrix has 45006 columns, and it will follow the sane organization in the other variable.

You can check on this section:
Tutorials/HeadModel - Brainstorm