Initial stresses of Step8 in the example of section 7.17(P205 Version2.2.1)

Dear CIG Team,
I’m trying to reappear the suit of examples in section 7.17. When I run the step8, the manual hinted the first step is to comment out the lines with the CellFilterAvg stiings of the pylithapp.cfg so as to got the stress tensor components of every quadrature point; then using the Python script to generate the spatial databases of the initial stresses. I opened this Python file and wanted to see the detials. I’m finding that there is a array named gpts in this file. So I wants to asking are the values of this gpts array the weight-value of quadrature point? And if I wanted to use the triangle cells, how can I give this gpts array and modified this Python script file?
Thanks for your helps.

The values of the gpts array are the basis functions evaluated at the quadrature points. We use this matrix to compute the coordinates of the quadrature points from the coordinates of the vertices of a cell.

In general within a cell, we have f(x,y) = sum_i a_i(x,y) * f_i where a_i are the basis functions evaluated at (x,y) and f_i are the coefficients for field i. In this example, a_i(x,y) are the basis functions evaluated at the quadrature points (gpts) and f_i are the coordinates of the vertices.