Convex hulls and mesh boundaries

Triangle produces the convex hull of a point set as a by-product in a .poly file when the -c switch is used. (The same can be done for PSLGs with the addition of the -O switch, which prevents holes from being carved.) In the example below, the file dots.node is read, and its convex hull produced in dots.1.poly. 
triangle -c dots

When Triangle is used to refine a preexisting mesh, the -c switch will instead produce a PSLG that specifies all the boundaries (including boundaries of holes) of the mesh. This PSLG will also include internal boundaries if and only if the -p switch is used and a .poly file exists for the preexisting mesh.

For example, consider the mesh described by face.1.node, face.1.ele, and face.1.poly (which you saw created on the Delaunay triangulation page).

triangle -rc face.1
triangle -rpc face.1
In each case, the boundary segments can be found in face.2.poly.

Return to Triangle home page.
jrs@cs.cmu.edu