Support reading of TetGen .ele files

CHANGELOG.md

@@ -3,6 +3,10 @@
 # [1.17.0] - 2026-04-15
 - new kwargs `not_in_domain_value = nothing` and `check_if_not_in_domain = isnothing(not_in_domain_value)` for grid interpolation.
   This enables the user to interpolate values between grids which do not share the same domain. The value _outside_ the target domain has to be provided by the user.
+- Allow to read simplexgrid data from TetGen .ele file sets
+
+## [1.16.0] - 2026-01-21
+- Allow to read/write WIAS-TeSCA dom files
 
 ## [1.15.0] - 2026-01-14
  - add and export `explode` function that produces a grid with all adjacencies removed

src/io.jl

@@ -55,6 +55,7 @@ $(TYPEDSIGNATURES)
      - format version 2.1: shortened version only with cells, cellnodes, cellregions, bfacenodes, bfaceregions
      - format version 2.2: like 2.1, but additional info on cell and node partitioning. Edge partitioning
        is not  stored in the file and may be re-established by [`induce_edge_partitioning!`](@ref).
+  - "*.ele": TetGen output format (requires presence of *.ele, *.node and *.face file)
   - "*.geo": gmsh geometry description (requires `using Gmsh`)
   - "*.msh": gmsh mesh (requires `using Gmsh`)
   - "*.dom": WIAS-TeSCA dom format
@@ -265,6 +266,95 @@ function writegrid(fname::String, g::ExtendableGrid, ::Type{Val{:sg}}; version =
     return nothing
 end
 
+########################################################
+## TetGen ele format
+#######################################################
+function simplexgrid(file::String, ::Type{Val{:ele}}; kwargs...)
+    Ti = Cint
+    fname, fext = splitext(file)
+    tks_ele = TokenStream(fname * ".ele")
+    tks_face = TokenStream(fname * ".face")
+    tks_node = TokenStream(fname * ".node")
+
+
+    npoints = parse(Ti, gettoken(tks_node))
+    dim = parse(Ti, gettoken(tks_node))
+    if dim != 3
+        throw(ErrorException("Dimension $dim not supported so far for .ele format"))
+    end
+    npointboundarymarkers = parse(Ti, gettoken(tks_node))
+    if npointboundarymarkers > 0
+        @warn "ignoring point boundary markers"
+    end
+    npointattributes = parse(Ti, gettoken(tks_node))
+    if npointattributes > 0
+        @warn "ignoring point attributes"
+    end
+    coord = Array{Float64, 2}(undef, dim, npoints)
+    for ipoint in 1:npoints
+        idx = parse(Ti, gettoken(tks_node)) + 1
+        for idim in 1:dim
+            coord[idim, idx] = parse(Float64, gettoken(tks_node))
+        end
+        for i in 1:npointboundarymarkers
+            gettoken(tks_node)
+        end
+        for i in 1:npointattributes
+            gettoken(tks_node)
+        end
+    end
+
+
+    ncells = parse(Ti, gettoken(tks_ele))
+    ncellnodes = parse(Ti, gettoken(tks_ele))
+    ncellattributes = parse(Ti, gettoken(tks_ele))
+    cells = Array{Ti, 2}(undef, ncellnodes, ncells)
+    regions = Array{Ti, 1}(undef, ncells)
+    if ncellattributes > 1
+        @warn "ignoring more than one cell attribute"
+    end
+    for icell in 1:ncells
+        idx = parse(Ti, gettoken(tks_ele)) + 1
+        for inode in 1:ncellnodes
+            cells[inode, idx] = parse(Ti, gettoken(tks_ele)) + 1
+        end
+        if ncellattributes == 0
+            regions[idx] = 1
+        else
+            regions[idx] = parse(Ti, gettoken(tks_ele))
+            for i in 2:ncellattributes
+                gettoken(tks_ele)
+            end
+        end
+    end
+
+    nfaces = parse(Ti, gettoken(tks_face))
+    nfaceattributes = parse(Ti, gettoken(tks_face))
+    nfacenodes = 3
+    if nfaceattributes > 1
+        @warn "ignoring more than one face attribute"
+    end
+    faces = Array{Ti, 2}(undef, dim, nfaces)
+    bregions = Array{Ti, 1}(undef, nfaces)
+    for iface in 1:nfaces
+        idx = parse(Ti, gettoken(tks_face)) + 1
+        for inode in 1:nfacenodes
+            faces[inode, idx] = parse(Ti, gettoken(tks_face)) + 1
+        end
+        if nfaceattributes == 0
+            bregions[idx] = 1
+        else
+            bregions[idx] = parse(Ti, gettoken(tks_face))
+            for i in 2:nfaceattributes
+                gettoken(tks_face)
+            end
+        end
+    end
+    g = simplexgrid(coord, cells, regions, faces, bregions)
+    return g
+end
+
+
 ########################################################
 ## WIAS-TeSCA dom format
 #######################################################

test/cube.1.edge

@@ -0,0 +1,50 @@
+48  1
+    0     22    42  -1
+    1     15    66  -1
+    2      6    41  -1
+    3     57   130  -1
+    4      5    74  -1
+    5     25   150  -1
+    6      1    83  -1
+    7      0   126  -1
+    8     38     6  -1
+    9     21    38  -1
+   10     16   112  -1
+   11      3   129  -1
+   12      3   154  -1
+   13     39    75  -1
+   14      7    82  -1
+   15     11   114  -1
+   16      4   149  -1
+   17     23   139  -1
+   18     17    87  -1
+   19      2   117  -1
+   20     19    51  -1
+   21      1    72  -1
+   22      2    98  -1
+   23     20    76  -1
+   24     41    19  -1
+   25     42     6  -1
+   26     51     7  -1
+   27      4   134  -1
+   28     66     7  -1
+   29     72    25  -1
+   30     74    22  -1
+   31     75     3  -1
+   32     76     4  -1
+   33     82    20  -1
+   34     83    57  -1
+   35     87     1  -1
+   36     98    39  -1
+   37    112     0  -1
+   38    114     0  -1
+   39    117    21  -1
+   40    126    17  -1
+   41    129    15  -1
+   42    130     2  -1
+   43    134    16  -1
+   44    139     5  -1
+   45    149    23  -1
+   46    150     5  -1
+   47    154    11  -1
+# Generated by /home/fuhrmann/Wias/work/tetgen/codeberg/TestingDrafts/src/../tetgen-v161/build/tetgen -pqa0.005 /home/fuhrmann/Wias/work/tetgen/codeberg/TestingDrafts/src/../quarry/cube.smesh