Minimum angle mesh quality criterion consists of calculation of the minimum value of angle between two adjacent sides of a 2D meshing element (triangle or quadrangle).
To apply the Minimum angle quality criterion to your mesh:
Display your mesh in the viewer.
Choose Controls > Face Controls > Minimum angle or click "Minimum Angle" button.
Your mesh will be displayed in the viewer with its elements colored according to the applied mesh quality control criterion:
See Also a sample TUI Script of a Minimum Angle quality control operation.