3D Tetrahedralizations

These examples can be loaded into Julia (Revise.jl recommended)

These examples retur an ExtendableGrid with default simplex grid data.

The control flags for TetGen are created based on default options provided by this module which try to ensure "good" grids for FEM and FVM computations. These are documented in default_options Occasional options! statements in the examples overwrite these defaults.

Domain triangulation

Here we just describe a domain as a polygon and mesh it. This test code is released under the license conditions of TetGen.jl

using SimplexGridFactory
using ExtendableGrids
using LinearAlgebra
using TetGen


function tetrahedralization_of_cube()

    builder=SimplexGridBuilder(Generator=TetGen)

    p1=point!(builder,0,0,0)
    p2=point!(builder,1,0,0)
    p3=point!(builder,1,1,0)
    p4=point!(builder,0,1,0)
    p5=point!(builder,0,0,1)
    p6=point!(builder,1,0,1)
    p7=point!(builder,1,1,1)
    p8=point!(builder,0,1,1)

    facetregion!(builder,1)
    facet!(builder,p1 ,p2 ,p3 ,p4)
    facetregion!(builder,2)
    facet!(builder,p5 ,p6 ,p7 ,p8)
    facetregion!(builder,3)
    facet!(builder,p1 ,p2 ,p6 ,p5)
    facetregion!(builder,4)
    facet!(builder,p2 ,p3 ,p7 ,p6)
    facetregion!(builder,5)
    facet!(builder,p3 ,p4 ,p8 ,p7)
    facetregion!(builder,6)
    facet!(builder,p4 ,p1 ,p5 ,p8)

    simplexgrid(builder,maxvolume=0.001)
end

Cube based on primitves

We can also use predefined primitives to combine geometries

function tet_cube_with_primitives()

    builder=SimplexGridBuilder(Generator=TetGen)
    facetregion!(builder,1)
    cellregion!(builder,1)
    maxvolume!(builder,0.1)
    regionpoint!(builder,(0.5,0.5,0.5))
    rect3d!(builder,(0,0,0), (10,10,10))

    facetregion!(builder, 2)
    cellregion!(builder,2)
    maxvolume!(builder,0.05)
    regionpoint!(builder,(4.5,4.5,4.5))
    rect3d!(builder,(3,3,3), (5,5,6))


    facetregion!(builder, 3)
    cellregion!(builder,3)
    maxvolume!(builder,0.025)
    regionpoint!(builder,(7,7,5))
    sphere!(builder,(7,7,5),2,nref=3)

    facetregion!(builder, 4)
    holepoint!(builder, (2,7,5))
    sphere!(builder,(2,7,5),1.5,nref=3)

    simplexgrid(builder)
end

Glue-in of existing grid

The bregions! method allows to extract parts of the geometry description from an already existing grid.

function glue_3d()
    h0=1.0
    X0=-2:h0:12
    Z0=-2:h0:6
    g0=simplexgrid(X0,X0,Z0)


    h=0.25
    X=0:h:10
    Z=0:h:4

    grid3=simplexgrid(X,X,Z)
    b=SimplexGridBuilder(Generator=TetGen)

    bregions!(b,g0,1:6;facetregions=[8 for i=1:7])
    cellregion!(b,2)
    regionpoint!(b,(-1,-1,-1))

    bregions!(b,grid3,1:6)
    holepoint!(b,(5,5,2))
    gouter=simplexgrid(b,maxvolume=0.4,nosteiner=true)
    glue(gouter,grid3,g1regions=1:6,interface=7)
end

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