A very simply set set of points to test the tripack functions, taken
from the FORTRAN original.
tritest2 is a slight modification by
runif(,-0.1,0.1) random numbers to the coordinates.
R. J. Renka (1996). Algorithm 751: TRIPACK: a constrained two-dimensional Delaunay triangulation package. ACM Transactions on Mathematical Software. 22, 1-8.