# MeshOverrideStructure

Defines an object that is only used in the process of generating the mesh.

A MeshOverrideStructure combines a geometry with grid sizes along the x, y, and z directions and controls whether the override is enforced.

# Override Type

In the editor, choose by grid size to set the override cell sizes, or by medium to select a medium for the override region. The editor also exposes Priority and, for by grid size, the Advanced options Enforce, Shadow, and Drop Outside Simulation.

# Name

name: Optional name for the structure.

Type: string

  • Default: None

# Geometry

geometry: Defines geometric properties of the structure.

Options:

# Override by Medium

background_medium: Medium used for the background of this structure when performing shape optimization with autograd. This is required when the structure is embedded in another structure as autograd will use the permittivity of the Simulation by default to compute the shape derivatives.

When by medium is selected, choose a medium from the medium selector. The editor saves the override as a plain Structure with this medium. The grid in this region is then generated as if the region were filled with that medium. The structure is used only for meshing. The grid-size and Advanced fields do not apply in this mode.

Options:

# Override by Grid Size

dl: Grid size along x, y, and z directions.

Type: floating-point numbers

  • Unit: μm
  • Constraint: each value greater than 0 when provided
  • Required field

# Enforce Grid Size

enforce: If True, enforce the grid size setup inside the structure even if the structure is inside a structure of smaller grid size. In the intersection region of multiple structures of enforce=True, grid size is decided by the last added structure of enforce=True.

Type: boolean

  • Default: False

# Shadow

shadow: In structure intersection region, grid size is decided by the latter added structure in the structure list when shadow=True; or the structure of smaller grid size when shadow=False. If shadow=False, and the structure doesn't refine the mesh, grid snapping to the bounding box of the structure is disabled.

Type: boolean

  • Default: True

# Drop Outside Simulation

drop_outside_sim: If True, structure outside the simulation domain is dropped; if False, structure takes effect along the dimensions where the projections of the structure and that of the simulation domain overlap.

Type: boolean

  • Default: True

# Priority

priority: Priority used when overlapping mesh override regions are resolved. Higher-priority overrides take precedence; equal priorities use the later structure.

Type: integer

  • Unit: unitless
  • Default: 0