Interpolates magnetic field value from field values on a given grid. More...

#include <Acts/MagneticField/InterpolatedBFieldMap.hpp>

Inheritance diagram for Acts::InterpolatedBFieldMap< grid_t >:

Collaboration diagram for Acts::InterpolatedBFieldMap< grid_t >:

Classes
struct	Cache
	Cache for field cell to improve performance of field lookups. More...
struct	Config
	Config structure for the interpolated B field map. More...
struct	FieldCell
	struct representing smallest grid unit in magnetic field grid More...

Public Types
using	FieldType = typename Grid::value_type
	Type alias for magnetic field vector type.
using	Grid = grid_t
	Type alias for magnetic field grid.
Public Types inherited from Acts::MagneticFieldProvider
using	Cache = Acts::AnyBase<sizeof(char) * 512>
	Opaque cache type that can store arbitrary implementation specific cache data.

Public Member Functions
	InterpolatedBFieldMap (Config cfg)
	default constructor
Result< Vector3 >	getField (const Vector3 &position) const
	retrieve field at given position
Result< Vector3 >	getField (const Vector3 &position, MagneticFieldProvider::Cache &cache) const final
	Retrieve magnetic field value at a given location.
Result< FieldCell >	getFieldCell (const Vector3 &position) const
	retrieve field cell for given position
Vector3	getFieldUnchecked (const Vector3 &position) const final
	Get magnetic field value without bounds checking (faster).
const Grid &	getGrid () const
	Get a const reference on the underlying grid structure.
std::vector< double >	getMax () const final
	get the maximum value of all axes of the field map
std::vector< double >	getMin () const final
	get the minimum value of all axes of the field map
std::vector< std::size_t >	getNBins () const final
	get the number of bins for all axes of the field map
bool	isInside (const Vector3 &position) const final
	check whether given 3D position is inside look-up domain
bool	isInsideLocal (const ActsVector< DIM_POS > &gridPosition) const
	check whether given 3D position is inside look-up domain
MagneticFieldProvider::Cache	makeCache (const MagneticFieldContext &mctx) const final
	Make an opaque cache for the magnetic field.
Public Member Functions inherited from Acts::MagneticFieldProvider
virtual	~MagneticFieldProvider ()=default

Static Public Attributes
static constexpr std::size_t	DIM_POS = Grid::DIM
	Dimensionality of the position space for field interpolation.

Detailed Description

template<typename grid_t>
class Acts::InterpolatedBFieldMap< grid_t >

Interpolates magnetic field value from field values on a given grid.

This class implements a magnetic field service which is initialized by a field map defined by:

a list of field values on a regular grid in some n-dimensional space,
a transformation of global 3D coordinates onto this n-dimensional space.
a transformation of local n-Dimensional magnetic field coordinates into global (cartesian) 3D coordinates

The magnetic field value for a given global position is then determined by:

mapping the position onto the grid,
looking up the magnetic field values on the closest grid points,
doing a linear interpolation of these magnetic field values.

Internally, this class uses a field interpolation cell to speed up lookups. This cell contains the interpolation points so the grid does not have to be consulted for each lookup. Explicit methods to create such a field cell are provided, but field cell creation is automatically handled by Acts::InterpolatedBFieldMap::makeCache, opaque to the client.

This class can leverage spatial symmetries in the magnetic field distribution. For cylindrically symmetric fields (e.g., solenoids, toroids), a 2D rz map can be used instead of a full 3D xyz map, significantly reducing memory requirements and improving performance. Helper functions Acts::fieldMapRZ and Acts::fieldMapXYZ are provided to construct field maps with the appropriate symmetries.

Template Parameters

grid_t The Grid type which provides the field storage and interpolation

Member Typedef Documentation

◆ FieldType

template<typename grid_t>

using Acts::InterpolatedBFieldMap< grid_t >::FieldType = typename Grid::value_type

Type alias for magnetic field vector type.

◆ Grid

template<typename grid_t>

using Acts::InterpolatedBFieldMap< grid_t >::Grid = grid_t

Type alias for magnetic field grid.

Constructor & Destructor Documentation

◆ InterpolatedBFieldMap()

template<typename grid_t>

Acts::InterpolatedBFieldMap< grid_t >::InterpolatedBFieldMap ( Config cfg )

explicit

default constructor

Parameters

cfg	Configuration containing grid and scaling factor

Member Function Documentation

◆ getField() [1/2]

template<typename grid_t>

Result< Vector3 > Acts::InterpolatedBFieldMap< grid_t >::getField ( const Vector3 & position ) const

retrieve field at given position

Parameters

[in] position global 3D position

Returns: magnetic field value at the given position

Precondition: The given position must lie within the range of the underlying magnetic field map.

◆ getField() [2/2]

template<typename grid_t>

Result< Vector3 > Acts::InterpolatedBFieldMap< grid_t >::getField	(	const Vector3 &	position,
		MagneticFieldProvider::Cache &	cache ) const

finalvirtual

Retrieve magnetic field value at a given location.

Requires an instance of Acts::MagneticFieldProvider::Cache created through makeCache.

Parameters

[in]	position	global 3D position for the lookup
[in,out]	cache	Field provider specific cache object

Returns: magnetic field vector at given position

Implements Acts::MagneticFieldProvider.

◆ getFieldCell()

template<typename grid_t>

Result< FieldCell > Acts::InterpolatedBFieldMap< grid_t >::getFieldCell ( const Vector3 & position ) const

retrieve field cell for given position

Parameters

[in] position global 3D position

Returns: field cell containing the given global position

Precondition: The given position must lie within the range of the underlying magnetic field map.

◆ getFieldUnchecked()

template<typename grid_t>

Vector3 Acts::InterpolatedBFieldMap< grid_t >::getFieldUnchecked ( const Vector3 & position ) const

finalvirtual

Get magnetic field value without bounds checking (faster).

Parameters

position Global 3D position for the lookup

Returns: Magnetic field value at the given position

Warning: No bounds checking is performed. The caller must ensure the position is within the valid range of the field map.

Implements Acts::InterpolatedMagneticField.

◆ getGrid()

template<typename grid_t>

const Grid & Acts::InterpolatedBFieldMap< grid_t >::getGrid ( ) const

Get a const reference on the underlying grid structure.

Returns: grid reference

◆ getMax()

template<typename grid_t>

std::vector< double > Acts::InterpolatedBFieldMap< grid_t >::getMax ( ) const

finalvirtual

get the maximum value of all axes of the field map

Returns: vector returning the maxima of all field map axes

Implements Acts::InterpolatedMagneticField.

◆ getMin()

template<typename grid_t>

std::vector< double > Acts::InterpolatedBFieldMap< grid_t >::getMin ( ) const

finalvirtual

get the minimum value of all axes of the field map

Returns: vector returning the minima of all field map axes

Implements Acts::InterpolatedMagneticField.

◆ getNBins()

template<typename grid_t>

std::vector< std::size_t > Acts::InterpolatedBFieldMap< grid_t >::getNBins ( ) const

finalvirtual

get the number of bins for all axes of the field map

Returns: vector returning number of bins for all field map axes

Implements Acts::InterpolatedMagneticField.

◆ isInside()

template<typename grid_t>

bool Acts::InterpolatedBFieldMap< grid_t >::isInside ( const Vector3 & position ) const

finalvirtual

check whether given 3D position is inside look-up domain

Parameters

[in] position global 3D position

Returns: true if position is inside the defined look-up grid, otherwise false

Implements Acts::InterpolatedMagneticField.

◆ isInsideLocal()

template<typename grid_t>

bool Acts::InterpolatedBFieldMap< grid_t >::isInsideLocal ( const ActsVector< DIM_POS > & gridPosition ) const

check whether given 3D position is inside look-up domain

Parameters

[in] gridPosition local N-D position

Returns: true if position is inside the defined look-up grid, otherwise false

◆ makeCache()

template<typename grid_t>

MagneticFieldProvider::Cache Acts::InterpolatedBFieldMap< grid_t >::makeCache ( const MagneticFieldContext & mctx ) const

finalvirtual

Make an opaque cache for the magnetic field.

Instructs the specific implementation to generate a Acts::MagneticFieldProvider::Cache instance for magnetic field lookup.

Parameters

mctx	The magnetic field context to generate cache for

Returns: Cache The opaque cache object

Implements Acts::MagneticFieldProvider.

Member Data Documentation

◆ DIM_POS

template<typename grid_t>

std::size_t Acts::InterpolatedBFieldMap< grid_t >::DIM_POS = Grid::DIM

staticconstexpr

Dimensionality of the position space for field interpolation.

Classes

Public Types

Public Member Functions

Static Public Attributes

Detailed Description

Member Typedef Documentation

◆ FieldType

◆ Grid

Constructor & Destructor Documentation

◆ InterpolatedBFieldMap()

Member Function Documentation

◆ getField() [1/2]

◆ getField() [2/2]

◆ getFieldCell()

◆ getFieldUnchecked()

◆ getGrid()

◆ getMax()

◆ getMin()

◆ getNBins()

◆ isInside()

◆ isInsideLocal()

◆ makeCache()

Member Data Documentation

◆ DIM_POS