vtkGenericCellTessellator Class Reference

#include <vtkGenericCellTessellator.h>

Inheritance diagram for vtkGenericCellTessellator:

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Collaboration diagram for vtkGenericCellTessellator:

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List of all members.

Detailed Description

helper class to perform cell tessellation

vtkGenericCellTessellator is a helper class to perform adaptive tessellation of particular cell topologies. The major purpose for this class is to transform higher-order cell types (e.g., higher-order finite elements) into linear cells that can then be easily visualized by VTK. This class works in conjunction with the vtkGenericDataSet and vtkGenericAdaptorCell classes.

This algorithm is based on edge subdivision. An error metric along each edge is evaluated, and if the error is greater than some tolerance, the edge is subdivided (as well as all connected 2D and 3D cells). The process repeats until the error metric is satisfied.

A significant issue addressed by this algorithm is to insure face compatibility across neigboring cells. That is, diagonals due to face triangulation must match to insure that the mesh is compatible. The algorithm employs a precomputed table to accelerate the tessellation process. The table was generated with the help of vtkOrderedTriangulator; the basic idea is that the choice of diagonal is made by considering the relative value of the point ids.

Definition at line 56 of file vtkGenericCellTessellator.h.


Public Types
typedef vtkObject	Superclass
Public Member Functions
virtual const char *	GetClassName ()
virtual int	IsA (const char *type)
void	PrintSelf (ostream &os, vtkIndent indent)
virtual void	Initialize (vtkGenericDataSet *ds)=0
void	InitErrorMetrics (vtkGenericDataSet *ds)
void	GetMaxErrors (double *errors)

virtual void	TessellateFace (vtkGenericAdaptorCell cell, vtkGenericAttributeCollection att, vtkIdType index, vtkDoubleArray points, vtkCellArray cellArray, vtkPointData *internalPd)=0

virtual void	Tessellate (vtkGenericAdaptorCell cell, vtkGenericAttributeCollection att, vtkDoubleArray points, vtkCellArray cellArray, vtkPointData *internalPd)=0

virtual void	Triangulate (vtkGenericAdaptorCell cell, vtkGenericAttributeCollection att, vtkDoubleArray points, vtkCellArray cellArray, vtkPointData *internalPd)=0

virtual void	SetErrorMetrics (vtkCollection *someErrorMetrics)
virtual vtkCollection *	GetErrorMetrics ()

virtual int	GetMeasurement ()
virtual void	SetMeasurement (int)
Static Public Member Functions
static int	IsTypeOf (const char *type)
static vtkGenericCellTessellator *	SafeDownCast (vtkObject *o)
Protected Member Functions
	vtkGenericCellTessellator ()
	~vtkGenericCellTessellator ()
void	ResetMaxErrors ()
void	SetGenericCell (vtkGenericAdaptorCell *cell)

int	RequiresEdgeSubdivision (double left, double mid, double *right, double alpha)

virtual void	UpdateMaxError (double leftPoint, double midPoint, double *rightPoint, double alpha)
Protected Attributes
vtkCollection *	ErrorMetrics
vtkGenericDataSet *	DataSet
int	Measurement
double *	MaxErrors
int	MaxErrorsCapacity

Member Typedef Documentation

typedef vtkObject vtkGenericCellTessellator::Superclass

Reimplemented from vtkObject.

Reimplemented in vtkSimpleCellTessellator.

Definition at line 59 of file vtkGenericCellTessellator.h.

Constructor & Destructor Documentation

vtkGenericCellTessellator::vtkGenericCellTessellator ( ) [protected]

vtkGenericCellTessellator::~vtkGenericCellTessellator ( ) [protected]

Member Function Documentation

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

Reimplemented from vtkObject.

Reimplemented in vtkSimpleCellTessellator.

static int vtkGenericCellTessellator::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 vtkTypeMacro found in vtkSetGet.h.

Reimplemented from vtkObject.

Reimplemented in vtkSimpleCellTessellator.

virtual int vtkGenericCellTessellator::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 vtkTypeMacro found in vtkSetGet.h.

Reimplemented from vtkObject.

Reimplemented in vtkSimpleCellTessellator.

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

Reimplemented from vtkObject.

Reimplemented in vtkSimpleCellTessellator.

void vtkGenericCellTessellator::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 vtkObject.

Reimplemented in vtkSimpleCellTessellator.

virtual void vtkGenericCellTessellator::TessellateFace	(	vtkGenericAdaptorCell *	cell,
		vtkGenericAttributeCollection *	att,
		vtkIdType	index,
		vtkDoubleArray *	points,
		vtkCellArray *	cellArray,
		vtkPointData *	internalPd
	)			`[pure virtual]`

Tessellate a face of a 3D `cell'. The face is specified by the index value. The result is a set of smaller linear triangles in `cellArray' with `points' and point data `internalPd'.

Precondition:

cell_exists: cell!=0

valid_dimension: cell->GetDimension()==3

valid_index_range: (index>=0) && (index<cell->GetNumberOfBoundaries(2))

att_exists: att!=0

points_exists: points!=0

cellArray_exists: cellArray!=0

internalPd_exists: internalPd!=0

Implemented in vtkSimpleCellTessellator.

virtual void vtkGenericCellTessellator::Tessellate	(	vtkGenericAdaptorCell *	cell,
		vtkGenericAttributeCollection *	att,
		vtkDoubleArray *	points,
		vtkCellArray *	cellArray,
		vtkPointData *	internalPd
	)			`[pure virtual]`

Tessellate a 3D `cell'. The result is a set of smaller linear tetrahedra in `cellArray' with `points' and point data `internalPd'.

Precondition:

cell_exists: cell!=0

valid_dimension: cell->GetDimension()==3

att_exists: att!=0

points_exists: points!=0

cellArray_exists: cellArray!=0

internalPd_exists: internalPd!=0

Implemented in vtkSimpleCellTessellator.

virtual void vtkGenericCellTessellator::Triangulate	(	vtkGenericAdaptorCell *	cell,
		vtkGenericAttributeCollection *	att,
		vtkDoubleArray *	points,
		vtkCellArray *	cellArray,
		vtkPointData *	internalPd
	)			`[pure virtual]`

Triangulate a 2D `cell'. The result is a set of smaller linear triangles in `cellArray' with `points' and point data `internalPd'.

Precondition:

cell_exists: cell!=0

valid_dimension: cell->GetDimension()==2

att_exists: att!=0

points_exists: points!=0

cellArray_exists: cellArray!=0

internalPd_exists: internalPd!=0

Implemented in vtkSimpleCellTessellator.

virtual void vtkGenericCellTessellator::SetErrorMetrics ( vtkCollection * someErrorMetrics ) [virtual]

Specify the list of error metrics used to decide if an edge has to be splitted or not. It is a collection of vtkGenericSubdivisionErrorMetric-s.

virtual vtkCollection* vtkGenericCellTessellator::GetErrorMetrics ( ) [virtual]

Specify the list of error metrics used to decide if an edge has to be splitted or not. It is a collection of vtkGenericSubdivisionErrorMetric-s.

virtual void vtkGenericCellTessellator::Initialize ( vtkGenericDataSet * ds ) [pure virtual]

Initialize the tessellator with a data set `ds'.

Implemented in vtkSimpleCellTessellator.

void vtkGenericCellTessellator::InitErrorMetrics ( vtkGenericDataSet * ds )

Init the error metric with the dataset. Should be called in each filter before any tessellation of any cell.

virtual int vtkGenericCellTessellator::GetMeasurement ( ) [virtual]

If true, measure the quality of the fixed subdivision.

virtual void vtkGenericCellTessellator::SetMeasurement ( int ) [virtual]

If true, measure the quality of the fixed subdivision.

void vtkGenericCellTessellator::GetMaxErrors ( double * errors )

Get the maximum error measured after the fixed subdivision.

Precondition:: errors_exists: errors!=0
valid_size: sizeof(errors)==GetErrorMetrics()->GetNumberOfItems()

int vtkGenericCellTessellator::RequiresEdgeSubdivision	(	double *	left,
		double *	mid,
		double *	right,
		double	alpha
	)			`[protected]`

Does the edge need to be subdivided according to at least one error metric? The edge is defined by its `leftPoint' and its `rightPoint'. `leftPoint', `midPoint' and `rightPoint' have to be initialized before calling RequiresEdgeSubdivision(). Their format is global coordinates, parametric coordinates and point centered attributes: xyx rst abc de... `alpha' is the normalized abscissa of the midpoint along the edge. (close to 0 means close to the left point, close to 1 means close to the right point)

Precondition:

leftPoint_exists: leftPoint!=0

midPoint_exists: midPoint!=0

rightPoint_exists: rightPoint!=0

clamped_alpha: alpha>0 && alpha<1

valid_size: sizeof(leftPoint)=sizeof(midPoint)=sizeof(rightPoint) =GetAttributeCollection()->GetNumberOfPointCenteredComponents()+6

virtual void vtkGenericCellTessellator::UpdateMaxError	(	double *	leftPoint,
		double *	midPoint,
		double *	rightPoint,
		double	alpha
	)			`[protected, virtual]`

Update the max error of each error metric according to the error at the mid-point. The type of error depends on the state of the concrete error metric. For instance, it can return an absolute or relative error metric. See RequiresEdgeSubdivision() for a description of the arguments.

Precondition:

leftPoint_exists: leftPoint!=0

midPoint_exists: midPoint!=0

rightPoint_exists: rightPoint!=0

clamped_alpha: alpha>0 && alpha<1

valid_size: sizeof(leftPoint)=sizeof(midPoint)=sizeof(rightPoint) =GetAttributeCollection()->GetNumberOfPointCenteredComponents()+6

void vtkGenericCellTessellator::ResetMaxErrors ( ) [protected]

Reset the maximal error of each error metric. The purpose of the maximal error is to measure the quality of a fixed subdivision.

void vtkGenericCellTessellator::SetGenericCell ( vtkGenericAdaptorCell * cell ) [protected]

Send the current cell to error metrics. Should be called at the beginning of the implementation of Tessellate(), Triangulate() or TessellateFace()