Class Acts::Surface¶

class Surface : public virtual Acts::GeometryObject, public std::enable_shared_from_this<Surface>¶
Abstract Base Class for tracking surfaces.
The Surface class builds the core of the Acts Tracking Geometry. All other geometrical objects are either extending the surface or are built from it.
Surfaces are either owned by Detector elements or the Tracking Geometry, in which case they are not copied within the data model objects.
Subclassed by Acts::ConeSurface, Acts::CylinderSurface, Acts::DiscSurface, Acts::LineSurface, Acts::PlaneSurface
Public Types
Public Functions

virtual ~Surface()¶

AlignmentToBoundMatrix alignmentToBoundDerivative(const GeometryContext &gctx, const FreeVector ¶meters, const FreeVector &pathDerivative) const¶
The derivative of bound track parameters w.r.t.
alignment parameters of its reference surface (i.e. local frame origin in global 3D Cartesian coordinates and its rotation represented with extrinsic Euler angles)
 Parameters
gctx – The current geometry context object, e.g. alignment change of alignment parameters
parameters – is the free parameters
pathDerivative – is the derivative of free parameters w.r.t. path length
 Returns
Derivative of bound track parameters w.r.t. local frame alignment parameters

virtual AlignmentToPathMatrix alignmentToPathDerivative(const GeometryContext &gctx, const FreeVector ¶meters) const¶
Calculate the derivative of path length at the geometry constraint or pointofclosestapproach w.r.t.
alignment parameters of the surface (i.e. local frame origin in global 3D Cartesian coordinates and its rotation represented with extrinsic Euler angles)
Note
Reimplementation is needed for surface whose intersection with track is not its local xy plane, e.g. LineSurface, CylinderSurface and ConeSurface
 Parameters
gctx – The current geometry context object, e.g. alignment
parameters – is the free parameters
 Returns
Derivative of path length w.r.t. the alignment parameters
Assign the surface material description.
The material is usually derived in a complicated way and loaded from a framework given source. As various surfaces may share the same source this is provided by a shared pointer
 Parameters
material – Material description associated to this surface

const DetectorElementBase *associatedDetectorElement() const¶
Return method for the associated Detector Element.
 Returns
plain pointer to the DetectorElement, can be nullptr

const Layer *associatedLayer() const¶
Return method for the associated Layer in which the surface is embedded.
 Returns
Layer by plain pointer, can be nullptr

void associateLayer(const Layer &lay)¶
Set Associated Layer Many surfaces can be associated to a Layer, but it might not be known yet during construction of the layer, this can be set afterwards.
 Parameters
lay – the assignment Layer by reference

virtual const SurfaceBounds &bounds() const = 0¶
Return method for SurfaceBounds.
 Returns
SurfaceBounds by reference

virtual BoundToFreeMatrix boundToFreeJacobian(const GeometryContext &gctx, const BoundVector &boundParams) const¶
Calculate the jacobian from local to global which the surface knows best, hence the calculation is done here.
Note
In principle, the input could also be a free parameters vector as it could be transformed to a bound parameters. But the transform might fail in case the parameters is not on surface. To avoid the check inside this function, it takes directly the bound parameters as input (then the check might be done where this function is called).
 Parameters
gctx – The current geometry context object, e.g. alignment
boundParams – is the bound parameters vector
 Returns
Jacobian from local to global

virtual Vector3 center(const GeometryContext &gctx) const¶
Return method for the surface center by reference.
Note
the center is always recalculated in order to not keep a cache
 Parameters
gctx – The current geometry context object, e.g. alignment
 Returns
center position by value

virtual FreeToBoundMatrix freeToBoundJacobian(const GeometryContext &gctx, const FreeVector ¶meters) const¶
Calculate the jacobian from global to local which the surface knows best, hence the calculation is done here.
Note
It assumes the input free parameters is on surface, hence no onSurface check is done inside this function.
 Parameters
gctx – The current geometry context object, e.g. alignment
parameters – is the free parameters
 Returns
Jacobian from global to local

virtual FreeToPathMatrix freeToPathDerivative(const GeometryContext &gctx, const FreeVector ¶meters) const¶
Calculate the derivative of path length at the geometry constraint or pointofclosestapproach w.r.t.
free parameters. The calculation is identical for all surfaces where the reference frame does not depend on the direction
 Parameters
gctx – The current geometry context object, e.g. alignment
parameters – is the free parameters
 Returns
Derivative of path length w.r.t. free parameters
Retrieve a
std::shared_ptr
for this surface (nonconst version)Note
Will error if this was not created through the
makeShared
factory since it needs access to the original reference. In C++14 this is undefined behavior (but most likely implemented as abad_weak_ptr
exception), in C++17 it is defined as that exception.Note
Only call this if you need shared ownership of this object.
 Returns
The shared pointer
Retrieve a
std::shared_ptr
for this surface (const version)Note
Will error if this was not created through the
makeShared
factory since it needs access to the original reference. In C++14 this is undefined behavior, but most likely implemented as abad_weak_ptr
exception, in C++17 it is defined as that exception.Note
Only call this if you need shared ownership of this object.
 Returns
The shared pointer

virtual Result<Vector2> globalToLocal(const GeometryContext &gctx, const Vector3 &position, const Vector3 &momentum, double tolerance = s_onSurfaceTolerance) const = 0¶
Global to local transformation Generalized global to local transformation for the surface types.
Since some surface types need the global momentum/direction to resolve sign ambiguity this is also provided
 Parameters
gctx – The current geometry context object, e.g. alignment
position – global 3D position  considered to be on surface but not inside bounds (check is done)
momentum – global 3D momentum representation (optionally ignored)
tolerance – optional tolerance within which a point is considered valid on surface
 Returns
a Result<Vector2> which can be !ok() if the operation fails

virtual bool insideBounds(const Vector2 &lposition, const BoundaryCheck &bcheck = true) const¶
The insideBounds method for local positions.
 Parameters
lposition – The local position to check
bcheck – BoundaryCheck directive for this onSurface check
 Returns
boolean indication if operation was successful

virtual SurfaceIntersection intersect(const GeometryContext &gctx, const Vector3 &position, const Vector3 &direction, const BoundaryCheck &bcheck) const = 0¶
Straight line intersection schema from position/direction.
 Parameters
gctx – The current geometry context object, e.g. alignment
position – The position to start from
direction – The direction at start
bcheck – the Boundary Check
 Returns
SurfaceIntersection object (contains intersection & surface)

bool isOnSurface(const GeometryContext &gctx, const Vector3 &position, const Vector3 &momentum, const BoundaryCheck &bcheck = true) const¶
The geometric onSurface method.
Geometrical check whether position is on Surface
 Parameters
gctx – The current geometry context object, e.g. alignment
position – global position to be evaludated
momentum – global momentum (required for linetype surfaces)
bcheck – BoundaryCheck directive for this onSurface check
 Returns
boolean indication if operation was successful

virtual ActsMatrix<2, 3> localCartesianToBoundLocalDerivative(const GeometryContext &gctx, const Vector3 &position) const = 0¶
Calculate the derivative of bound track parameters local position w.r.t.
position in local 3D Cartesian coordinates
 Parameters
gctx – The current geometry context object, e.g. alignment
position – The position of the paramters in global
 Returns
Derivative of bound local position w.r.t. position in local 3D cartesian coordinates

virtual Vector3 localToGlobal(const GeometryContext &gctx, const Vector2 &lposition, const Vector3 &momentum) const = 0¶
Local to global transformation Generalized local to global transformation for the surface types.
Since some surface types need the global momentum/direction to resolve sign ambiguity this is also provided
 Parameters
gctx – The current geometry context object, e.g. alignment
lposition – local 2D position in specialized surface frame
momentum – global 3D momentum representation (optionally ignored)
 Returns
The global position by value

virtual std::string name() const = 0¶
Return properly formatted class name.

virtual Vector3 normal(const GeometryContext &gctx, const Vector2 &lposition) const = 0¶
Return method for the normal vector of the surface The normal vector can only be generally defined at a given local position It requires a local position to be given (in general)
 Parameters
gctx – The current geometry context object, e.g. alignment
lposition – is the local position where the normal vector is constructed
 Returns
normal vector by value

virtual Vector3 normal(const GeometryContext &gctx, const Vector3 &position) const¶
Return method for the normal vector of the surface The normal vector can only be generally defined at a given local position It requires a local position to be given (in general)
 Parameters
position – is the global position where the normal vector is constructed
gctx – The current geometry context object, e.g. alignment
 Returns
normal vector by value

inline virtual Vector3 normal(const GeometryContext &gctx) const¶
Return method for the normal vector of the surface.
It will return a normal vector at the center() position
 Parameters
gctx – The current geometry context object, e.g. alignment
 Returns
normal vector by value

virtual bool operator!=(const Surface &sf) const¶
Comparison (nonequality) operator.
 Parameters
sf – Source surface for the comparison

Surface &operator=(const Surface &other)¶
Assignment operator.
Note
copy construction invalidates the association to detector element and layer
 Parameters
other – Source surface for the assignment

virtual bool operator==(const Surface &other) const¶
Comparison (equality) operator The strategy for comparison is (a) first pointer comparison (b) then type comparison (c) then bounds comparison (d) then transform comparison.
 Parameters
other – source surface for the comparison

virtual double pathCorrection(const GeometryContext &gctx, const Vector3 &position, const Vector3 &direction) const = 0¶
Calucation of the path correction for incident.
 Parameters
gctx – The current geometry context object, e.g. alignment
position – global 3D position  considered to be on surface but not inside bounds (check is done)
direction – global 3D momentum direction
 Returns
Path correction with respect to the nominal incident.

virtual Polyhedron polyhedronRepresentation(const GeometryContext &gctx, size_t lseg) const = 0¶
Return a Polyhedron for this object.
Note
An internal surface transform can invalidate the extrema in the transformed space
 Parameters
gctx – The current geometry context object, e.g. alignment
lseg – Number of segments along curved lines, if the lseg is set to one, only the corners and the extrema are given, otherwise it represents the number of segments for a full 2*M_PI circle and is scaled to the relevant sector
 Returns
A list of vertices and a face/facett description of it

virtual Acts::RotationMatrix3 referenceFrame(const GeometryContext &gctx, const Vector3 &position, const Vector3 &momentum) const¶
Return mehtod for the reference frame This is the frame in which the covariance matrix is defined (specialized by all surfaces)
 Parameters
gctx – The current geometry context object, e.g. alignment
position – global 3D position  considered to be on surface but not inside bounds (check is done)
momentum – global 3D momentum representation (optionally ignored)
 Returns
RotationMatrix3 which defines the three axes of the measurement frame

const ISurfaceMaterial *surfaceMaterial() const¶
Return method for the associated Material to this surface.
 Returns
SurfaceMaterial as plain pointer, can be nullptr
Return method for the shared pointer to the associated Material.
 Returns
SurfaceMaterial as shared_pointer, can be nullptr

virtual std::ostream &toStream(const GeometryContext &gctx, std::ostream &sl) const¶
Output Method for std::ostream, to be overloaded by child classes.
 Parameters
gctx – The current geometry context object, e.g. alignment
sl – is the ostream to be dumped into

virtual const Transform3 &transform(const GeometryContext &gctx) const¶
Return method for the surface Transform3 by reference In case a detector element is associated the surface transform is just forwarded to the detector element in order to keep the (mis)alignment cache cetrally handled.
 Parameters
gctx – The current geometry context object, e.g. alignment
 Returns
the contextual transform

virtual SurfaceType type() const = 0¶
Return method for the Surface type to avoid dynamic casts.
Public Static Functions
Factory for producing memory managed instances of Surface.
Will forward all parameters and will attempt to find a suitable constructor.

virtual ~Surface()¶