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Merge pull request #52 from gwater/dev_msh
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Implement basic parser for triangular meshes from .MSH version 4 (GMSH)
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@SimonDanisch
SimonDanisch authored Mar 23, 2020
2 parents 135b0cb + 3c08e40 commit 321115d
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Showing 4 changed files with 302 additions and 1 deletion.
4 changes: 3 additions & 1 deletion src/MeshIO.jl
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Expand Up @@ -6,7 +6,8 @@ using ColorTypes
using Printf
import FileIO

import FileIO: DataFormat, @format_str, Stream, File, filename, stream, skipmagic
import FileIO: DataFormat, @format_str, Stream, File, filename, stream,
skipmagic, add_format
import Base.show


Expand All @@ -16,6 +17,7 @@ include("io/ply.jl")
include("io/stl.jl")
include("io/obj.jl")
include("io/2dm.jl")
include("io/msh.jl")

load(fn::File{format}, MeshType=GLNormalMesh) where {format} = open(fn) do s
skipmagic(s)
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128 changes: 128 additions & 0 deletions src/io/msh.jl
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@@ -0,0 +1,128 @@

function load(fs::Stream{format"MSH"}, MeshType=GLNormalMesh)
#GMSH MSH format (version 4)
#http://gmsh.info/doc/texinfo/gmsh.html#MSH-file-format
io = stream(fs)

FaceType = facetype(MeshType)
VertexType = vertextype(MeshType)
faces = FaceType[]
nodes = VertexType[]
node_tags = Int[]

while !eof(io)
BlockType = _parse_blocktype!(io)
if BlockType == MSHNodesBlock()
_parse_nodes!(io, nodes, node_tags)
elseif BlockType == MSHElementsBlock()
_parse_elements!(io, faces)
else
_skip_block!(io)
end
end

_remap_faces!(faces, node_tags)

return MeshType(nodes, faces)
end

struct MSHFormatBlock end
struct MSHNodesBlock end
struct MSHElementsBlock end
struct MSHUnknownBlock end

function _parse_blocktype!(io)
header = readline(io)
if header == "\$MeshFormat"
return MSHFormatBlock()
elseif header == "\$Nodes"
return MSHNodesBlock()
elseif header == "\$Elements"
return MSHElementsBlock()
else
return MSHUnknownBlock()
end
end

function _parse_format!(io)
version, binary, size = map(parse, (Float64, Int, Int), split(readline(io)))
if version < 4
error("version $(version[1]) < 4.0 not supported.")
elseif binary == 1
error("binary format not supported.")
end
endblock = readline(io)
if endblock != "\$EndMeshFormat"
error("expected block end tag, got $endblock.")
end
return version
end

function _skip_block!(io)
while true
line = readline(io)
if line[1:4] == "\$End"
break
end
end
return nothing
end

function _parse_nodes!(io, nodes, node_tags)
numEntityBlocks, numNodes, minNodeTag, maxNodeTag =
map(parse, (Int, Int, Int, Int), split(readline(io)))
for index_entity in 1:numEntityBlocks
entityDim, entityTag, parametric, numNodesInBlock =
map(parse, (Int, Int, Int, Int), split(readline(io)))
for i in 1:numNodesInBlock
push!(node_tags, parse(eltype(node_tags), readline(io)))
end
for i in 1:numNodesInBlock
x, y, z = map(parse, (Float64, Float64, Float64), split(readline(io)))
push!(nodes, eltype(nodes)(x, y, z))
end
end
endblock = readline(io)
if endblock != "\$EndNodes"
error("expected end block tag, got $endblock")
end
return nodes, node_tags
end

function _parse_elements!(io, faces::Vector{T}) where T <: Triangle
numEntityBlocks, numElements, minElementTag, maxElementTag =
map(parse, (Int, Int, Int, Int), split(readline(io)))
for index_entity in 1:numEntityBlocks
entityDim, entityTag, elementType, numElementsInBlock =
map(parse, (Int, Int, Int, Int), split(readline(io)))
if elementType == 2 # Triangles
for i in 1:numElementsInBlock
tag, n1, n2, n3 =
map(parse, (Int, Int, Int, Int), split(readline(io)))
push!(faces, eltype(faces)(n1, n2, n3))
end
else
# for now we ignore all other elements (points, lines, hedrons, etc)
for i in 1:numElementsInBlock
readline(io)
end
end
end
endblock = readline(io)
if endblock != "\$EndElements"
error("expected end block tag, got $endblock")
end
return faces
end

function _remap_faces!(faces, node_tags)
node_map = indexin(1:maximum(node_tags), node_tags)
for (i, face) in enumerate(faces)
faces[i] = eltype(faces)(
node_map[face[1]],
node_map[face[2]],
node_map[face[3]]
)
end
return faces
end
7 changes: 7 additions & 0 deletions test/runtests.jl
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Expand Up @@ -158,6 +158,13 @@ end
#@test length(vertices(msh)) == 2248
#@test length(normals(msh)) == 2248
end
@testset "GMSH" begin
msh = load(joinpath(tf, "cube.msh"))
@test typeof(msh) == GLNormalMesh
@test length(faces(msh)) == 24
@test length(vertices(msh)) == 14
test_face_indices(msh)
end
end
end

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164 changes: 164 additions & 0 deletions test/testfiles/cube.msh
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$MeshFormat
4.1 0 8
$EndMeshFormat
$Entities
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1 -1e-07 -9.999999994736442e-08 -9.999999994736442e-08 1e-07 1.0000001 1.0000001 0 4 1 2 -3 -4
2 0.9999999000000001 -9.999999994736442e-08 -9.999999994736442e-08 1.0000001 1.0000001 1.0000001 0 4 5 6 -7 -8
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5 -9.999999994736442e-08 -9.999999994736442e-08 -1e-07 1.0000001 1.0000001 1e-07 0 4 4 11 -8 -9
6 -9.999999994736442e-08 -9.999999994736442e-08 0.9999999000000001 1.0000001 1.0000001 1.0000001 0 4 2 12 -6 -10
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$EndEntities
$Nodes
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0 1 0 1
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0 0 1
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$EndNodes
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$EndElements

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