vtkLabelHierarchy Class Reference

#include <vtkLabelHierarchy.h>

Inheritance diagram for vtkLabelHierarchy:

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Collaboration diagram for vtkLabelHierarchy:

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List of all members.

Detailed Description

contains an octree of labels

This class represents labels in a hierarchy used to denote rendering priority. A binary tree of labels is maintained that subdivides the bounds of the of the label anchors spatially. Which level of the tree a label occupies determines its priority; those at higher levels of the tree will be more likely to render than those at lower levels of the tree.

Pass vtkLabelHierarchy objects to a vtkLabelPlacer filter for dynamic, non-overlapping, per-frame placement of labels.

Note that if we have a d-dimensional binary tree and we want a fixed number $n$ of labels in each node (all nodes, not just leaves), we can compute the depth of tree required assuming a uniform distribution of points. Given a total of $N$ points we know that $\frac{N}{|T|} = n$ , where $|T|$ is the cardinality of the tree (i.e., the number of nodes it contains). Because we have a uniform distribution, the tree will be uniformly subdivided and thus $|T| = 1 + 2^d + \left(2^d\right)^2 + \cdots + \left(2^d\right)^k$ , where $d$ is the dimensionality of the input points (fixed at 3 for now). As $k$ becomes large, $|T|\approx 2 \left(2^d\right)^k$ . Using this approximation, we can solve for $k$ :

$k = \frac{\log{\frac{N}{2n}}}{\log{2^d}}$

Given a set of $N$ input label anchors, we'll compute $k$ and then bin the anchors into tree nodes at level $k$ of the tree. After this, all the nodes will be in the leaves of the tree and those leaves will be at the $k$ -th level; no anchors will be in levels $1, 2, \ldots, k-1$ . To fix that, we'll choose to move some anchors upwards. The exact number to move upwards depends on TargetLabelCount. We'll move as many up as required to have TargetLabelCount at each node.

You should avoid situations where MaximumDepth does not allow for TargetLabelCount or fewer entries at each node. The MaximumDepth is a hard limit while TargetLabelCount is a suggested optimum. You will end up with many more than TargetLabelCount entries per node and things will be sloooow.

Tests:: vtkLabelHierarchy (Tests)

Definition at line 76 of file vtkLabelHierarchy.h.


Public Types
typedef vtkPointSet	Superclass

enum	IteratorType { FULL_SORT, QUEUE, DEPTH_FIRST, FRUSTUM }
Public Member Functions
virtual const char *	GetClassName ()
virtual int	IsA (const char *type)
virtual void	PrintSelf (ostream &os, vtkIndent indent)
virtual void	SetPoints (vtkPoints *)
virtual void	ComputeHierarchy ()
void	GetDiscreteNodeCoordinatesFromWorldPoint (int ijk[3], double pt[3], int level)
Implementation *	GetImplementation ()

virtual void	SetTargetLabelCount (int)
virtual int	GetTargetLabelCount ()

virtual void	SetMaximumDepth (int)
virtual int	GetMaximumDepth ()

virtual void	SetPriorities (vtkDataArray *arr)
virtual vtkDataArray *	GetPriorities ()

vtkLabelHierarchyIterator *	NewIterator (int type, vtkRenderer ren, vtkCamera cam, double frustumPlanes[24], bool positionsAsNormals, float bucketSize[2])

virtual vtkIdType	GetNumberOfCells ()
virtual vtkCell *	GetCell (vtkIdType)
virtual void	GetCell (vtkIdType, vtkGenericCell *)
virtual int	GetCellType (vtkIdType)
virtual void	GetCellPoints (vtkIdType, vtkIdList *)
virtual void	GetPointCells (vtkIdType, vtkIdList *)
virtual vtkIdType	FindCell (double , vtkCell , vtkIdType, double, int &, double , double )
virtual vtkIdType	FindCell (double , vtkCell , vtkGenericCell , vtkIdType, double, int &, double , double *)
virtual int	GetMaxCellSize ()

virtual vtkPoints *	GetCenterPts ()

virtual vtkCoincidentPoints *	GetCoincidentPoints ()
Static Public Member Functions
static vtkLabelHierarchy *	New ()
static int	IsTypeOf (const char *type)
static vtkLabelHierarchy *	SafeDownCast (vtkObject *o)
static bool	GetPathForNodalCoordinates (int *path, int ijk[3], int level)
Protected Member Functions
	vtkLabelHierarchy ()
virtual	~vtkLabelHierarchy ()
Protected Attributes
int	TargetLabelCount
int	MaximumDepth
vtkDataArray *	Priorities
vtkCoincidentPoints *	CoincidentPoints
vtkPoints *	CenterPts
Implementation *	Impl
Friends
class	vtkLabelHierarchyFrustumIterator
class	vtkLabelHierarchyFullSortIterator
class	implementation
Classes
class	Implementation

Member Typedef Documentation

typedef vtkPointSet vtkLabelHierarchy::Superclass

Reimplemented from vtkPointSet.

Definition at line 80 of file vtkLabelHierarchy.h.

Member Enumeration Documentation

enum vtkLabelHierarchy::IteratorType

Enumeration of iterator types.

Enumerator:

FULL_SORT
QUEUE
DEPTH_FIRST
FRUSTUM

Definition at line 106 of file vtkLabelHierarchy.h.

Constructor & Destructor Documentation

vtkLabelHierarchy::vtkLabelHierarchy ( ) [protected]

virtual vtkLabelHierarchy::~vtkLabelHierarchy ( ) [protected, virtual]

Member Function Documentation

static vtkLabelHierarchy* vtkLabelHierarchy::New ( ) [static]

Create an object with Debug turned off, modified time initialized to zero, and reference counting on.

Reimplemented from vtkDataObject.

virtual const char* vtkLabelHierarchy::GetClassName ( ) [virtual]

Reimplemented from vtkPointSet.

static int vtkLabelHierarchy::IsTypeOf ( const char * name ) [static]

Return 1 if this class type is the same type of (or a subclass of) the named class. Returns 0 otherwise. This method works in combination with vtkTypeRevisionMacro found in vtkSetGet.h.

Reimplemented from vtkPointSet.

virtual int vtkLabelHierarchy::IsA ( const char * name ) [virtual]

Return 1 if this class is the same type of (or a subclass of) the named class. Returns 0 otherwise. This method works in combination with vtkTypeRevisionMacro found in vtkSetGet.h.

Reimplemented from vtkPointSet.

static vtkLabelHierarchy* vtkLabelHierarchy::SafeDownCast ( vtkObject * o ) [static]

Reimplemented from vtkPointSet.

virtual void vtkLabelHierarchy::PrintSelf	(	ostream &	os,
		vtkIndent	indent
	)			`[virtual]`

Methods invoked by print to print information about the object including superclasses. Typically not called by the user (use Print() instead) but used in the hierarchical print process to combine the output of several classes.

Reimplemented from vtkPointSet.

virtual void vtkLabelHierarchy::SetPoints ( vtkPoints * ) [virtual]

Override SetPoints so we can reset the hierarchy when the points change.

Reimplemented from vtkPointSet.

virtual void vtkLabelHierarchy::ComputeHierarchy ( ) [virtual]

Fill the hierarchy with the input labels.

virtual void vtkLabelHierarchy::SetTargetLabelCount ( int ) [virtual]

The number of labels that is ideally present at any octree node. It is best if this is a multiple of $2^d$ .

virtual int vtkLabelHierarchy::GetTargetLabelCount ( ) [virtual]

The number of labels that is ideally present at any octree node. It is best if this is a multiple of $2^d$ .

virtual void vtkLabelHierarchy::SetMaximumDepth ( int ) [virtual]

The maximum depth of the octree.

virtual int vtkLabelHierarchy::GetMaximumDepth ( ) [virtual]

The maximum depth of the octree.

virtual void vtkLabelHierarchy::SetPriorities ( vtkDataArray * arr ) [virtual]

Set/get the array specifying the importance (priority) of each label.

virtual vtkDataArray* vtkLabelHierarchy::GetPriorities ( ) [virtual]

Set/get the array specifying the importance (priority) of each label.

vtkLabelHierarchyIterator* vtkLabelHierarchy::NewIterator	(	int	type,
		vtkRenderer *	ren,
		vtkCamera *	cam,
		double	frustumPlanes[24],
		bool	positionsAsNormals,
		float	bucketSize[2]
	)

Returns an iterator for this data object. positionsAsNormals should only be true when labels are on a sphere centered at the origin (3D world).

Parameters:

	type	- the type should be one of FULL_SORT, QUEUE, DEPTH_FIRST, or FRUSTUM.
	ren	- the current renderer (used for viewport information)
	cam	- the current camera.
	frustumPlanes	- should be the output of the camera's frustum planes.
	positionsAsNormals	- throws out octree nodes on the opposite side of the origin.
	bucketSize	- an array of 2 integers describing the width and height of label placer buckets.

void vtkLabelHierarchy::GetDiscreteNodeCoordinatesFromWorldPoint	(	int	ijk[3],
		double	pt[3],
		int	level
	)

Given a depth in the hierarchy (level) and a point pt in world space, compute ijk. This is used to find other octree nodes at the same level that are within the search radius for candidate labels to be placed. It is called with pt set to the camera eye point and pythagorean quadruples increasingly distant from the origin are added to ijk to identify octree nodes whose labels should be placed.

Parameters:

`[out]`	ijk	- discrete coordinates of the octree node at level containing pt.
`[in]`	pt	- input world point coordinates
`[in]`	level	- input octree level to be considered

static bool vtkLabelHierarchy::GetPathForNodalCoordinates	(	int *	path,
		int	ijk[3],
		int	level
	)			`[static]`

Given a level of the tree and ijk coordinates in a lattice, compute a path down the tree to reach the corresponding lattice node. If the lattice coordinates are outside the tree, this returns false. Otherwise it returns true. This does not guarantee that the path exists in the hierarchy.

Parameters:

`[out]`	path	- a vector of level integers specifying which child to descend at each level to reach ijk
`[in]`	ijk	- discrete coordinates of the octree node at level
`[in]`	level	- input octree level to be considered

virtual vtkIdType vtkLabelHierarchy::GetNumberOfCells ( ) [virtual]