Computes projection matrix elements for VoxelsOnCartesianGrid images by using a Length of Intersection (LOI) model. More...

#include "stir_experimental/recon_buildblock/ProjMatrixByDenselUsingRayTracing.h"

Inheritance diagram for stir::ProjMatrixByDenselUsingRayTracing:

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Public Member Functions
	ProjMatrixByDenselUsingRayTracing ()
	Default constructor (calls set_defaults())

void	set_up (const shared_ptr< const ProjDataInfo > &proj_data_info_ptr, const shared_ptr< const DiscretisedDensity< 3, float >> &density_info_ptr) override
	Stores all necessary geometric info. More...

const DataSymmetriesForDensels *	get_symmetries_ptr () const override
	get a pointer to an object encoding all symmetries that are used by this ProjMatrixByDensel

float	get_element (const Bin &, const CartesianCoordinate3D< float > &) const override
	this member computes a single element of the projection matrix More...

Public Member Functions inherited from stir::RegisteredParsingObject< ProjMatrixByDenselUsingRayTracing, ProjMatrixByDenselOnCartesianGridUsingElement >
std::string	get_registered_name () const override
	Returns Derived::registered_name.

std::string	parameter_info () override
	Returns a string with all parameters and their values, in a form suitable for parsing again.

Public Member Functions inherited from stir::ProjMatrixByDensel
void	get_proj_matrix_elems_for_one_densel (ProjMatrixElemsForOneDensel &, const Densel &) const
	The main method for getting a column of the matrix. More...

void	enable_cache (bool v)

Public Member Functions inherited from stir::ParsingObject
	ParsingObject (const ParsingObject &)

ParsingObject &	operator= (const ParsingObject &)

void	ask_parameters ()

bool	parse (std::istream &f)

bool	parse (const char *const filename)

Static Public Attributes
static const char *const	registered_name = "Ray Tracing"
	Name which will be used when parsing a ProjMatrixByDensel object.

Additional Inherited Members
Static Public Member Functions inherited from stir::RegisteredParsingObject< ProjMatrixByDenselUsingRayTracing, ProjMatrixByDenselOnCartesianGridUsingElement >
static ProjMatrixByDenselOnCartesianGridUsingElement *	read_from_stream (std::istream *)
	Construct a new object (of type Derived) by parsing the istream. More...

Static Public Member Functions inherited from stir::RegisteredObject< ProjMatrixByDensel >
static ProjMatrixByDensel *	read_registered_object (std::istream *in, const std::string &registered_name)
	Construct a new object (of a type derived from Root, its actual type determined by the registered_name parameter) by parsing the istream. More...

static ProjMatrixByDensel *	ask_type_and_parameters ()
	ask the user for the type, and then calls read_registered_object(0, type) More...

static void	list_registered_names (std::ostream &stream)
	List all possible registered names to the stream. More...

Protected Types inherited from stir::RegisteredObject< ProjMatrixByDensel >
typedef ProjMatrixByDensel (	RootFactory) (std::istream *)
	The type of a root factory is a function, taking an istream* as argument, and returning a Root*.

typedef FactoryRegistry< std::string, RootFactory, interfile_less >	RegistryType
	The type of the registry.

Protected Member Functions inherited from stir::ProjMatrixByDenselOnCartesianGridUsingElement
void	calculate_proj_matrix_elems_for_one_densel (ProjMatrixElemsForOneDensel &) const override
	Calculates all non-zero elements for a particular densel. More...

Protected Member Functions inherited from stir::ProjMatrixByDensel
	ProjMatrixByDensel ()
	default ctor (enables caching)

Succeeded	get_cached_proj_matrix_elems_for_one_densel (ProjMatrixElemsForOneDensel &) const
	The method that tries to get data from the cache. More...

void	cache_proj_matrix_elems_for_one_densel (const ProjMatrixElemsForOneDensel &) const
	The method to store data in the cache. More...

Protected Member Functions inherited from stir::ParsingObject
virtual void	set_key_values ()
	This will be called before parsing or parameter_info is called. More...

Static Protected Member Functions inherited from stir::RegisteredObject< ProjMatrixByDensel >
static RegistryType &	registry ()
	Static function returning the registry. More...

Protected Attributes inherited from stir::ProjMatrixByDenselOnCartesianGridUsingElement
shared_ptr< const ProjDataInfo >	proj_data_info_ptr

CartesianCoordinate3D< float >	grid_spacing

CartesianCoordinate3D< float >	origin

float	min_z_index

float	max_z_index

Protected Attributes inherited from stir::ProjMatrixByDensel
bool	cache_disabled

Protected Attributes inherited from stir::ParsingObject
KeyParser	parser

Detailed Description

Computes projection matrix elements for VoxelsOnCartesianGrid images by using a Length of Intersection (LOI) model.

Currently, the LOIs are divided by voxel_size.x(), unless NEWSCALE is #defined during compilation time of ProjMatrixByDenselUsingRayTracing.cxx.

If the z voxel size is exactly twice the sampling in axial direction, multiple LORs are used, to avoid missing voxels. (TODOdoc describe how).

Currently, a FOV is used which is circular, and is slightly 'inside' the image (i.e. the radius is about 1 voxel smaller than the maximum possible).

The implementation uses RayTraceVoxelsOnCartesianGrid().

Warning: Only appropriate for VoxelsOnCartesianGrid type of images (otherwise a run-time error occurs).; Current implementation assumes that x,y voxel sizes are at least as large as the sampling in tangential direction, and that z voxel size is either smaller than or exactly twice the sampling in axial direction of the segments.

Member Function Documentation

◆ set_up()

void stir::ProjMatrixByDenselUsingRayTracing::set_up	(	const shared_ptr< const ProjDataInfo > &	proj_data_info_ptr,
		const shared_ptr< const DiscretisedDensity< 3, float >> &	density_info_ptr
	)

overridevirtual

Stores all necessary geometric info.

Note that the density_info_ptr is not stored in this object. It's only used to get some info on sizes etc.

Reimplemented from stir::ProjMatrixByDenselOnCartesianGridUsingElement.

References stir::error(), stir::DiscretisedDensity< num_dimensions, elemT >::get_origin(), stir::Array< num_dimensions, elemT >::get_regular_range(), stir::VoxelsOnCartesianGrid< elemT >::get_voxel_size(), and stir::warning().

◆ get_element()

float stir::ProjMatrixByDenselUsingRayTracing::get_element	(	const Bin &	bin,
		const CartesianCoordinate3D< float > &	densel_ctr
	)		const

overridevirtual

this member computes a single element of the projection matrix

Parameters

bin	The bin-coordinates specifying the row of the projection matrix
densel_ctr	The densel coordinates specifying the column of the projection matrix

Returns: returns the value of the element

Ideally, get_element should be implemented such that tiny elements are truncated to 0, to avoid storing (and using) elements that not really contribute to the result.

Warning: Currently, the densel_ctr has to be in mm and w.r.t. the centre of the scanner. This is a bad idea (it should use dicrete coordinates) and so will change in the future. It's there now for the RT projector to avoid recomputing the coordinates per mm fo revery bin.

Implements stir::ProjMatrixByDenselOnCartesianGridUsingElement.

References _PI, stir::ProjDataInfoCylindricalNoArcCorr::get_det_num_pair_for_view_tangential_pos_num(), stir::Scanner::get_num_detectors_per_ring(), stir::ProjDataInfo::get_scanner_ptr(), stir::ProjDataInfo::get_t(), stir::ProjDataInfo::get_tantheta(), stir::square(), stir::Bin::tangential_pos_num(), and stir::ViewgramIndices::view_num().

The documentation for this class was generated from the following files:

/home/sirfuser/devel/STIRdistrib/STIR/src/include/stir_experimental/recon_buildblock/ProjMatrixByDenselUsingRayTracing.h
/home/sirfuser/devel/STIRdistrib/STIR/src/experimental/recon_buildblock/ProjMatrixByDenselUsingRayTracing.cxx

Public Member Functions

Static Public Attributes

Additional Inherited Members

Detailed Description

Member Function Documentation

◆ set_up()

◆ get_element()