Extract the Boundary of a 3D Mesh

Identifies the unshared edges of a 3D mesh, i.e., edges belonging to only one face. These edges can be returned either as vertex indices or as a mesh3d object consisting of the corresponding segments.

Usage

getBoundarySegments3(mesh, malla = FALSE, simplify = TRUE)

Arguments

mesh

A mesh3d object representing the 3D mesh.

malla

Logical. If TRUE, returns a mesh3d object containing the boundary segments; if FALSE, returns only the vertex indices forming the boundary edges. Default is FALSE.

simplify

Logical. If TRUE and malla = TRUE, simplifies the resulting mesh using cleanMesh3d_rgl(). Default is TRUE.

Value

If malla = FALSE, a matrix with the vertex indices forming the boundary edges. If malla = TRUE, a mesh3d object representing the boundary segments.

Details

This function is an adaptation of rgl::getBoundary3d(). Unlike the original version, which detects boundary edges by finding duplicates in the edge list, this implementation uses a frequency table (data.table) to count how many times each edge appears in the mesh faces. Edges that appear only once are considered boundary edges. Additionally, the function allows returning either the vertex indices of the boundary edges or a mesh3d mesh of the segments, with an optional additional simplification.

See also

rgl::getBoundary3d(), cleanMesh3d_rgl()

Examples

# Extract the boundary of a cube and visualize it
require(data.table)
#> Loading required package: data.table

# Create a cube and remove two faces
x <- rgl::cube3d(col = "lightblue")
x$ib <- x$ib[, -(1:2)]

# Generate the boundary
b <- getBoundarySegments3(x, malla = TRUE)

# Visualize the mesh and its boundary
rgl::open3d()
rgl::shade3d(x, alpha = 0.2)
rgl::shade3d(b, col = "red", lwd = 2)