Boundary markers

Boundary markers are tags used mainly to identify which output vertices and edges are associated with which PSLG segment, and to identify which vertices and edges occur on a boundary of the triangulation. A common use is to determine where boundary conditions should be applied to a finite element mesh. You can prevent boundary markers from being written into files produced by Triangle by using the -B switch.

The boundary marker associated with each segment in an output .poly file and each edge in an output .edge file is chosen as follows:

The boundary marker associated with each vertex in an output .node file is chosen as follows: If you want Triangle to determine for you which vertices and edges are on the boundary, assign them the boundary marker zero (or use no markers at all) in your input files. In the output files, all boundary vertices, edges, and segments will be assigned the value one.
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