Horizontal refinement

Horizontal mesh refinement (i.e. refinement of the column structure) can be carried out using the mesh refine() method. It is possible to refine only selected parts of the mesh using the columns parameter, which is a set, tuple or list of column objects to be refined.

For example:

cols = m.find((0, 0), (4000, 5000))
m.refine(cols)

will refine all mesh columns within the rectangle with lower left corner at the origin and upper right corner at (4000, 5000).

The selected columns are replaced by four refined columns (the edges of the original columns being subdivided in two). Triangular columns are added around the edge of the refinement area to make the transition from coarse to fine columns.

Note that the triangular transition columns created by refine() may not necessarily have desirable mesh quality statistics (e.g. aspect ratios or face orthogonality). Hence it is often necessary to follow the refine() command with a call to the optimize() method (see Optimizing a mesh), in order to regain acceptable mesh quality in the transition region.