pslg {RTriangle}

Create a Planar Straight Line Graph object

Description

A Planar Straight Line Graph (PSLG) is a collection of vertices and segments. Segments are edges whose endpoints are vertices in the PSLG, and whose presence in any mesh generated from the PSLG is enforced.

Usage

pslg(P, PB = NA, PA = NA, S = NA, SB = NA, H = NA)

Arguments

P

A 2-column matrix of x-y co-ordinates of vertices. There is one row per vertex.

PB

Vector of boundary markers of vertices. For each vertex this is 1 if the point should be on a boundary of any mesh generated from the PSLG and 0 otherwise. There should be as many elements in VB as there are vertices in V.

PA

Matrix of attributes which are typically floating-point values of physical quantities (such as mass or conductivity) associated with the nodes of a finite element mesh. When triangulating using triangulate these are copied unchanged to existing points in the output mesh and each new Steiner point added to the mesh will have quantities assigned to it by linear interpolation.

S

A 2-column matrix of segments in which each row is a segment. Segments are edges whose endpoints are vertices in the PSLG, and whose presence in any mesh generated from the PSLG is enforced. Each segment refers to the indices in V of the endpoints of the segment. By default the segments are not specified (NA), in which case the convex hull of the vertices are taken to be the segments. Any vertices outside the region enclosed by the segments are eaten away by the triangulation algorithm. If the segments do not enclose a region the whole triangulation may be eaten away.

SB

Vector of boundary markers of segments. For each segment this is 1 if the segment should be on a boundary of any mesh generated from the PSLG and 0 otherwise. There should be as many elements in SB as there are segments in S.

H

2-column matrix of holes, with one hole per row.Holes are specified by identifying a point inside each hole. After the triangulation is formed, Triangle creates holes by eating triangles, spreading out from each hole point until its progress is blocked by PSLG segments; you must be careful to enclose each hole in segments, or your whole triangulation might be eaten away. If the two triangles abutting a segment are eaten, the segment itself is also eaten. Do not place a hole directly on a segment; if you do, Triangle will choose one side of the segment arbitrarily.

Value

An object containing the input of type pslg that contains the information supplied in the inputs. This function does some sanity checking of its inputs.

Author(s)

David Sterratt