Connected Components of an Undirected Graph

Provides a function for fast computation of the connected components of an undirected graph (though not faster than the components() function of the 'igraph' package) from the edges or the adjacency matrix of the graph. Based on this one, a function to compute the connected components of a triangle 'rgl' mesh is also provided.

concom

Fast computation of the connected components of an undirected graph.

f <- function(x, y, z, a, cosb, sinb){
    (sqrt((sqrt(x*x + (y*sinb + a*cosb)^2) - 2)^2) - 1)^2 +
      (sqrt((sqrt(z*z + (y*cosb - a*sinb)^2) - 2)^2) - 1)^2
}
a <- 0.6
b <- 0.785
cosb <- cos(b)
sinb <- sin(b)

x <- z <- seq(-3.5, 3.5, len = 150L)
y <- seq(-4.2, 4.2, len = 150L)
g <- expand.grid(X = x, Y = y, Z = z)
voxel <- array(
  with(g, f(X, Y, Z, a, cosb, sinb)),
  dim = c(150L, 150L, 150L)
)

library(rmarchingcubes)
contour_shape <- contour3d(
  griddata = voxel,
  level = 0.1,
  x = x,
  y = y,
  z = z
)

library(rgl)
tmesh <- tmesh3d(
  vertices = t(contour_shape[["vertices"]]),
  indices = t(contour_shape[["triangles"]]),
  normals = contour_shape[["normals"]],
  homogeneous = FALSE
)
open3d(windowRect = c(50, 50, 562, 562), zoom = 0.9)
shade3d(tmesh, color = "orangered")

library(concom)
meshes <- concom3d(tmesh)

colors <- hcl.colors(length(meshes))
open3d(windowRect = c(50, 50, 562, 562), zoom = 0.9)
for(i in 1L:length(meshes)){
  shade3d(meshes[[i]], color = colors[i])
}