In MESH you can inverse the diagonal (edge) of a pseudo-quadrangle formed by two neighboring triangles with one common edge.
To inverse the diagonal:
1. From the Modification menu choose the Diagonal inversion item or click button in the toolbar. The following dialog box shall appear:
2. Enter the ID of the required edge in the Edge field or select this edge in the 3D viewer.
3. Click the Apply or OK button.
See Also a sample TUI Script of a Diagonal Inversion of Elements operation.