The -S switch

• Specifies the maximum number of Steiner points that may be inserted into the mesh (to meet the constraints of minimum angle and maximum area). Type an integer after the -S switch.
• The default (when -S is not used) is to allow an unlimited number.
• If you specify this switch with no number after it, the limit is set to zero.
• Triangle always adds points at segment intersections, even if it needs to use more points than the limit you set. When Triangle inserts segments by splitting (-s), it always adds enough points to ensure that all the segments appear in the triangulation, again ignoring the limit.
• Be forewarned that the -S switch may result in a conforming triangulation that is not truly Delaunay, because Triangle may be forced to stop adding points when the mesh is in a state where a segment is non-Delaunay and needs to be split. If so, Triangle will print a warning.