Materials

Material, Structure, and material sample types in WiTwin Core

Overview #

WiTwin Core defines the base material and structure types shared across all WiTwin solver packages. These are the same Material and Structure you use in witwin.channel and witwin.maxwell — they are re-exported from witwin.core.

from witwin.core import Box, Material, Structure
 
wall = Structure(
    name="wall",
    geometry=Box(position=(0.0, 0.0, 1.5), size=(0.25, 4.0, 3.0)),
    material=Material(eps_r=4.0, sigma_e=0.0),
)

Material #

Defines the electromagnetic properties of a surface.

Material(eps_r=4.0, mu_r=1.0, sigma_e=0.01, name="concrete")

Parameter	Type	Default	Description
`eps_r`	`float`	`1.0`	Relative permittivity
`mu_r`	`float`	`1.0`	Relative permeability
`sigma_e`	`float`	`0.0`	Electrical conductivity. Must be >= 0
`name`	`str \| None`	`None`	Optional material name

Methods #

material.evaluate_static() — Returns a StaticMaterialSample with eps_r, mu_r, sigma_e.

material.evaluate_at_frequency(frequency) — Returns a FrequencyMaterialSample with complex eps_r accounting for conductivity at the given frequency in Hz.

material.capabilities() — Returns a MaterialCapabilities describing which physical effects are active.

Structure #

Pairs a geometry with a material to create a physical object.

Structure(
    name="wall",
    geometry=Box(position=(0.0, 0.0, 1.5), size=(0.25, 4.0, 3.0)),
    material=Material(eps_r=4.0, sigma_e=0.0),
    priority=0,
    enabled=True,
)

Parameter	Type	Default	Description
`geometry`	`GeometryBase`	required	Any geometry primitive
`material`	`MaterialSpec`	required	Material defining EM properties
`name`	`str \| None`	`None`	Unique name. Required by `Scene`
`priority`	`int`	`0`	Priority for overlapping structures
`enabled`	`bool`	`True`	Whether this structure is included in simulation
`tags`	`tuple[str]`	`()`	Optional tags for grouping
`metadata`	`dict \| None`	`None`	Optional metadata

MaterialCapabilities #

Describes which physical effects are active for a material.

caps = material.capabilities()
print(caps.conductive)   # True if sigma_e > 0
print(caps.magnetic)     # True if mu_r != 1.0
print(caps.anisotropic)  # True if tensor properties are set
print(caps.dispersive)   # True if dispersion poles are set

Field	Type	Description
`conductive`	`bool`	Material has non-zero conductivity
`magnetic`	`bool`	Material has non-unity permeability
`anisotropic`	`bool`	Material uses tensor properties
`dispersive`	`bool`	Material uses dispersion poles

StaticMaterialSample #

Returned by material.evaluate_static().

Field	Description
`eps_r`	Relative permittivity (real)
`mu_r`	Relative permeability (real)
`sigma_e`	Electrical conductivity

FrequencyMaterialSample #

Returned by material.evaluate_at_frequency(frequency).

Field	Description
`eps_r`	Complex relative permittivity including conductivity loss
`mu_r`	Relative permeability
`sigma_e`	Electrical conductivity

MaterialSpec Protocol #

MaterialSpec is the protocol that all material types must satisfy. It requires:

name: str | None
capabilities() -> MaterialCapabilities
evaluate_static() -> StaticMaterialSample
evaluate_at_frequency(frequency) -> FrequencyMaterialSample

Both witwin.core.Material and witwin.maxwell.Material implement this protocol.

Next Steps #

Scene API — SceneBase reference
Mitsuba bridge — convert scenes to Mitsuba format