fdtdx.Sphere

Bases: StaticMultiMaterialObject

A sphere or ellipsoid object with configurable properties.

This class represents a sphere or ellipsoid with customizable radius/radii and material. When all three radii are equal, the shape is a perfect sphere.

Attributes:
  • radius (float) –

    The default radius of the sphere in meter (used if specific axis radii are not provided).

  • material_name (str) –

    Name of the sphere material in the materials dictionary to be used for the object.

  • radius_x (float | None) –

    The radius along the x-axis in meter. If none, use radius. Defaults to None.

  • radius_y (float | None) –

    The radius along the y-axis in meter. If none, use radius. Defaults to None.

  • radius_z (float | None) –

    The radius along the z-axis in meter. If none, use radius. Defaults to None.

get_voxel_mask_for_shape 

get_voxel_mask_for_shape() -> jax.Array

Generates a voxel mask for a sphere or ellipsoid shape.

Returns:
  • Array –

    jax.Array: Boolean mask where True indicates voxels inside the sphere/ellipsoid.
Source code in src/fdtdx/objects/static_material/sphere.py 
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def get_voxel_mask_for_shape(self) -> jax.Array:
    """Generates a voxel mask for a sphere or ellipsoid shape.

    Returns:
        jax.Array: Boolean mask where True indicates voxels inside the sphere/ellipsoid.
    """
    # Get dimensions
    x_dim, y_dim, z_dim = self.grid_shape

    # Define center of the ellipsoid
    center = (x_dim / 2, y_dim / 2, z_dim / 2)

    # Determine the radii for each axis
    radius_x = self.radius_x if self.radius_x is not None else self.radius
    radius_y = self.radius_y if self.radius_y is not None else self.radius
    radius_z = self.radius_z if self.radius_z is not None else self.radius

    # Convert radii to grid units
    grid_radius_x = radius_x / self._config.resolution
    grid_radius_y = radius_y / self._config.resolution
    grid_radius_z = radius_z / self._config.resolution

    # Create 3D grid
    x, y, z = jnp.meshgrid(jnp.arange(x_dim), jnp.arange(y_dim), jnp.arange(z_dim), indexing="ij")

    # Calculate normalized squared distances for each dimension using the ellipsoid equation
    x_term = ((x - center[0] + 0.5) / grid_radius_x) ** 2
    y_term = ((y - center[1] + 0.5) / grid_radius_y) ** 2
    z_term = ((z - center[2] + 0.5) / grid_radius_z) ** 2

    # Create mask based on ellipsoid equation: points inside if x^2/a^2 + y^2/b^2 + z^2/c^2 < 1
    mask = (x_term + y_term + z_term) < 1

    return mask