93 resolutionspec insideoutside entity

[simbilod]

add restrict field

[simbilod]

@fedeinthemix this PR adds a new attribute to ThresholdField and ExponentialField to restrict the field to a list of entities

This allows these fields to be only applied to one side of an interface. Should be useful for skin effect as discussed in #91

For instance:

for restrict_to in [None, ["inner_left"],  ["inner_right"],  ["outer", "inner_right"]]: 
    large_rect = 20
    small_rect = 5

    polygon1 = shapely.Polygon(
        [[0, 0], [large_rect, 0], [large_rect, large_rect], [0, large_rect], [0, 0]],
    )
    polygon2 = shapely.Polygon(
        [
            [large_rect / 2 - small_rect / 2, large_rect / 2 - small_rect / 2],
            [large_rect / 2 + small_rect / 2, large_rect / 2 - small_rect / 2],
            [large_rect / 2 + small_rect / 2, large_rect / 2 + small_rect / 2],
            [large_rect / 2 - small_rect / 2, large_rect / 2 + small_rect / 2],
            [large_rect / 2 - small_rect / 2, large_rect / 2 - small_rect / 2],
        ],
    )

    model = Model(n_threads=1)
    poly_outer = PolySurface(
        polygons=polygon1,
        model=model,
        mesh_order=2,
        physical_name="outer",
    )
    poly_left = PolySurface(
        polygons=shapely.affinity.translate(polygon2, xoff=-3.1),
        model=model,
        mesh_order=1,
        physical_name="inner_left",
        resolutions=[
            ThresholdField(
                sizemin=0.05,
                distmax=10,
                sizemax=1,
                apply_to="curves",
                restrict_to=restrict_to, # new argument
            )
        ],
    )
    poly_right = PolySurface(
        polygons=shapely.affinity.translate(polygon2, xoff=3.1),
        model=model,
        mesh_order=1,
        physical_name="inner_right",
    )
    entities_list = [poly_outer, poly_left, poly_right]
    model.mesh(
        entities_list=entities_list,
        default_characteristic_length=1,
        verbosity=0,
        filename=f"mesh_restrict_{restrict_to}.msh",
    )

Gives:

None (old behavior, default, isotropic field)

["inner_left"] (apply only inside)

["outer", "inner_right"] (apply only to the others listed)

You can add multiple fields to control the different interfaces differently:

    """Test different threshold fields on each side of an interface."""
    # Create outer square
    outer_square = shapely.Polygon([
        [0, 0], [10, 0], [10, 10], [0, 10], [0, 0]
    ])

    # Create inner square
    inner_square = shapely.Polygon([
        [4, 4], [6, 4], [6, 6], [4, 6], [4, 4]
    ])

    model = Model(n_threads=1)

    # Create outer polysurface with coarser exponential field
    poly_outer = PolySurface(
        polygons=outer_square,
        model=model,
        mesh_order=2,
        physical_name="outer",
        resolutions=[
            ExponentialField(
                sizemin=0.05,
                lengthscale=2.0,
                growth_factor=3,
                apply_to="curves",
                not_sharing=["None"],
                restrict_to=["outer"]
            )
        ]
    )

    # Create inner polysurface with finer exponential field
    poly_inner = PolySurface(
        polygons=inner_square,
        model=model,
        mesh_order=1,
        physical_name="inner",
        resolutions=[
            ExponentialField(
                sizemin=0.05
                lengthscale=0.5,  # Shorter transition distance
                growth_factor=3.0,
                apply_to="curves",
                restrict_to=["inner"]
            )
        ]
    )

    # Mesh the model
    model.mesh(
        entities_list=[poly_outer, poly_inner],
        default_characteristic_length=2.0,  # Increased default size
        verbosity=0,
        filename="mesh_interface_thresholds.msh"
    )

Closes #93

[fedeinthemix]

Nice, thank you!