Extract a list of triangles from a triangulation object
This function extracts a triangulation data structure
from an triangulation object created by tri.mesh.
The vertices in the returned matrix (let's denote it with
retval) are ordered
counterclockwise with the first vertex taken
to be the one with smallest index. Thus,
retval[i,"node2"] and retval[i,"node3"] are larger
than
retval[i,"node3"] and index adjacent neighbors of
node retval[i,"node1"]. The columns trx and
arcx, x=1,2,3 index the triangle and arc,
respectively, which are opposite (not shared
by) node nodex, with trix= 0 if
arcx indexes a boundary arc. Vertex
indexes range from 1 to N, triangle indexes
from 0 to NT, and, if included, arc indexes
from 1 to NA = NT+N-1. The triangles are
ordered on first (smallest) vertex indexes,
except that the sets of constraint triangles
(triangles contained in the closure of a constraint
region) follow the non-constraint
triangles.
triangles(tri.obj)
tri.obj |
object of class |
A matrix with columns node1,node2,node3,
representing the vertex nodal indexes,
tr1,tr2,tr3, representing neighboring triangle
indexes and arc1,arc2,arc3 reresenting arc indexes.
Each row represents one triangle.
A. Gebhardt
R. J. Renka (1996). Algorithm 751: TRIPACK: a constrained two-dimensional Delaunay triangulation package. ACM Transactions on Mathematical Software. 22, 1-8.
# use a slighlty modified version of data(tritest) data(tritest2) tritest2.tr<-tri.mesh(tritest2$x,tritest2$y) triangles(tritest2.tr)
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