Skip to contents

Construct dual maximum spanning forest on triangles

Source: R/utils_dmt.R
do_dual_forest.Rd

Constructs a directed maximum spanning forest from triangle and edge scalar values using a version of Prim's algorithm. Critical triangles (local maximum; or, more precisely, a triangle that contains an edge that is a local maximum) are used as roots for each tree in the forest, and edges that would bridge two trees with different critical triangle roots are marked as possible saddle edges.

Usage

do_dual_forest(dmt)

Arguments

dmt

A DMT data structure with the following attributes:

  • tris$f: Scalar field values defined for each triangle.

  • edges$from_tri: Index of first triangle joined by each edge.

  • edges$to_tri: Index of second triangle joined by each edge.

  • edges$f_dual: Scalar field values defined for each edge that connects two triangles.

Value

A List with the following attributes (all indices are 1-indexed):

  • edges: A data.table with forest_size rows, where each row is a directed edge in the maximum spanning forest. There are six columns:

    • from,to: Index of source and target triangles for each edge.

    • x0,y0: Coordinates of source triangle for each edge.

    • x1,y1: Coordinates of target triangle for each edge.

  • saddles: A length num_saddles vector with edge indices for possible saddle edges.

  • labels: A length num_triangles vector of labels for the connected components in the maximum spanning tree. Each connected component is labeled by the index of its critical triangle.

  • maxima: A length num_critpts vector of critical triangles (maxima).

  • parent: A length num_triangles vector containing the parent (source) triangle for each triangle in the directed spanning forest. Critical triangles have no parent, so the value should be ignored.

  • parent_edge: A length num_triangles vector containing the directed edge that has each triangle as a target node. Critical triangles have no parent edge, so the value should be ignored.