How can we calculate the effective mass along any direction like along x-axis, y-axis, Zaxis ? I have gone through the video https://youtu.be/QeM-YKEn74g?si=yoj6MYN0nGdqlvOB , where they have taken equal number of k points on both side and by fitting into a parabolic equation. Is the process same for both isotropic and anisotropic case. In case of anisotropic case how can we take the k points in X,Y,Z directions?