Layer-based Grid Refinement#

`tidy3d.LayerRefinementSpec`	Specification for automatic mesh refinement and snapping in layered structures.
`tidy3d.CornerFinderSpec`	Specification for corner detection on a 2D plane.
`tidy3d.GridRefinement`	Specification for local mesh refinement that defines the grid step size and the number of grid cells in the refinement region.

The LayerRefinementSpec class allows the user to specify automated refinement within a layered region, for instance, the metallic trace plane of a printed circuit board. The grid will be automatically refined near any metallic corners and edges in that layer.

import tidy3d as td
# Define layer refinement spec
my_layer_refinement_spec = td.LayerRefinementSpec(
    axis=2,  # layer normal axis
    center=(0, 0, 0),  # layer center
    size=(3, 2, 0.1),  # layer size
    min_steps_along_axis=2,  # minimum number of grid points along normal axis
    corner_refinement=td.GridRefinement(dl=100, num_cells=2)  # metal corner refinement specification
)

# Add layer refinement spec to overall grid specification
my_grid_spec = td.GridSpec(
    ...,
    layer_refinement_specs = [my_layer_refinement_spec]
)

More than one LayerRefinementSpec is permitted. In addition to manually defining the center and size of the LayerRefinementSpec, one can alternatively use the from_bounds(), from_layer_bounds(), or from_structures() convenience methods.

my_layer_refinement_spec_2 = LayerRefinementSpec.from_structures(
    structures=[my_planar_structure],   # position, size, and axis automatically determined based on structure
    ...
)

Note that different LayerRefinementSpec instances are recommended for structures on different physical layers.