vtkQuadricDecimation Class Reference

#include <vtkQuadricDecimation.h>

Inheritance diagram for vtkQuadricDecimation:

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Collaboration diagram for vtkQuadricDecimation:

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List of all members.

Detailed Description

reduce the number of triangles in a mesh

vtkQuadricDecimation is a filter to reduce the number of triangles in a triangle mesh, forming a good approximation to the original geometry. The input to vtkQuadricDecimation is a vtkPolyData object, and only triangles are treated. If you desire to decimate polygonal meshes, first triangulate the polygons with vtkTriangleFilter.

The algorithm is based on repeated edge collapses until the requested mesh reduction is achieved. Edges are placed in a priority queue based on the "cost" to delete the edge. The cost is an approximate measure of error (distance to the original surface)--described by the so-called quadric error measure. The quadric error measure is associated with each vertex of the mesh and represents a matrix of planes incident on that vertex. The distance of the planes to the vertex is the error in the position of the vertex (originally the vertex error iz zero). As edges are deleted, the quadric error measure associated with the two end points of the edge are summed (this combines the plane equations) and an optimal collapse point can be computed. Edges connected to the collapse point are then reinserted into the queue after computing the new cost to delete them. The process continues until the desired reduction level is reached or topological constraints prevent further reduction. Note that this basic algorithm can be extended to higher dimensions by taking into account variation in attributes (i.e., scalars, vectors, and so on).

This paper is based on the work of Garland and Heckbert who first presented the quadric error measure at Siggraph '97 "Surface Simplification Using Quadric Error Metrics". For details of the algorithm Michael Garland's Ph.D. thesis is also recommended. Hughues Hoppe's Vis '99 paper, "New Quadric Metric for Simplifying Meshes with Appearance Attributes" is also a good take on the subject especially as it pertains to the error metric applied to attributes.

Thanks:: Thanks to Bradley Lowekamp of the National Library of Medicine/NIH for contributing this class.

Tests:: vtkQuadricDecimation (Tests)

Definition at line 69 of file vtkQuadricDecimation.h.


Public Types
typedef vtkPolyDataAlgorithm	Superclass
Public Member Functions
virtual const char *	GetClassName ()
virtual int	IsA (const char *type)
void	PrintSelf (ostream &os, vtkIndent indent)

virtual void	SetTargetReduction (double)
virtual double	GetTargetReduction ()

virtual void	SetAttributeErrorMetric (int)
virtual int	GetAttributeErrorMetric ()
virtual void	AttributeErrorMetricOn ()
virtual void	AttributeErrorMetricOff ()

virtual void	SetScalarsAttribute (int)
virtual int	GetScalarsAttribute ()
virtual void	ScalarsAttributeOn ()
virtual void	ScalarsAttributeOff ()
virtual void	SetVectorsAttribute (int)
virtual int	GetVectorsAttribute ()
virtual void	VectorsAttributeOn ()
virtual void	VectorsAttributeOff ()
virtual void	SetNormalsAttribute (int)
virtual int	GetNormalsAttribute ()
virtual void	NormalsAttributeOn ()
virtual void	NormalsAttributeOff ()
virtual void	SetTCoordsAttribute (int)
virtual int	GetTCoordsAttribute ()
virtual void	TCoordsAttributeOn ()
virtual void	TCoordsAttributeOff ()
virtual void	SetTensorsAttribute (int)
virtual int	GetTensorsAttribute ()
virtual void	TensorsAttributeOn ()
virtual void	TensorsAttributeOff ()

virtual void	SetScalarsWeight (double)
virtual void	SetVectorsWeight (double)
virtual void	SetNormalsWeight (double)
virtual void	SetTCoordsWeight (double)
virtual void	SetTensorsWeight (double)
virtual double	GetScalarsWeight ()
virtual double	GetVectorsWeight ()
virtual double	GetNormalsWeight ()
virtual double	GetTCoordsWeight ()
virtual double	GetTensorsWeight ()

virtual double	GetActualReduction ()
Static Public Member Functions
static int	IsTypeOf (const char *type)
static vtkQuadricDecimation *	SafeDownCast (vtkObject *o)
static vtkQuadricDecimation *	New ()
Protected Member Functions
	vtkQuadricDecimation ()
	~vtkQuadricDecimation ()
int	RequestData (vtkInformation , vtkInformationVector , vtkInformationVector )
int	CollapseEdge (vtkIdType pt0Id, vtkIdType pt1Id)
void	InitializeQuadrics (vtkIdType numPts)
void	AddBoundaryConstraints (void)
void	ComputeQuadric (vtkIdType pointId)
void	AddQuadric (vtkIdType oldPtId, vtkIdType newPtId)
void	FindAffectedEdges (vtkIdType p1Id, vtkIdType p2Id, vtkIdList *edges)
vtkIdType	GetEdgeCellId (vtkIdType p1Id, vtkIdType p2Id)
int	IsGoodPlacement (vtkIdType pt0Id, vtkIdType pt1Id, const double *x)
int	TrianglePlaneCheck (const double t0[3], const double t1[3], const double t2[3], const double *x)
void	ComputeNumberOfComponents (void)
void	UpdateEdgeData (vtkIdType ptoId, vtkIdType pt1Id)
void	GetAttributeComponents ()

double	ComputeCost (vtkIdType edgeId, double *x)
double	ComputeCost2 (vtkIdType edgeId, double *x)

void	SetPointAttributeArray (vtkIdType ptId, const double *x)
void	GetPointAttributeArray (vtkIdType ptId, double *x)
Protected Attributes
double	TargetReduction
double	ActualReduction
int	AttributeErrorMetric
int	ScalarsAttribute
int	VectorsAttribute
int	NormalsAttribute
int	TCoordsAttribute
int	TensorsAttribute
double	ScalarsWeight
double	VectorsWeight
double	NormalsWeight
double	TCoordsWeight
double	TensorsWeight
int	NumberOfEdgeCollapses
vtkEdgeTable *	Edges
vtkIdList *	EndPoint1List
vtkIdList *	EndPoint2List
vtkPriorityQueue *	EdgeCosts
vtkDoubleArray *	TargetPoints
int	NumberOfComponents
vtkPolyData *	Mesh
ErrorQuadric *	ErrorQuadrics
int	AttributeComponents [6]
double	AttributeScale [6]
vtkIdList *	CollapseCellIds
double *	TempX
double *	TempQuad
double *	TempB
double **	TempA
double *	TempData
Classes
struct	ErrorQuadric

Member Typedef Documentation

typedef vtkPolyDataAlgorithm vtkQuadricDecimation::Superclass

Reimplemented from vtkPolyDataAlgorithm.

Definition at line 72 of file vtkQuadricDecimation.h.

Constructor & Destructor Documentation

vtkQuadricDecimation::vtkQuadricDecimation ( ) [protected]

vtkQuadricDecimation::~vtkQuadricDecimation ( ) [protected]

Member Function Documentation

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

Reimplemented from vtkPolyDataAlgorithm.

static int vtkQuadricDecimation::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 vtkPolyDataAlgorithm.

virtual int vtkQuadricDecimation::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 vtkPolyDataAlgorithm.

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

Reimplemented from vtkPolyDataAlgorithm.

void vtkQuadricDecimation::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 vtkPolyDataAlgorithm.

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

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

Reimplemented from vtkPolyDataAlgorithm.

virtual void vtkQuadricDecimation::SetTargetReduction ( double ) [virtual]

Set/Get the desired reduction (expressed as a fraction of the original number of triangles). The actual reduction may be less depending on triangulation and topological constraints.

virtual double vtkQuadricDecimation::GetTargetReduction ( ) [virtual]

Set/Get the desired reduction (expressed as a fraction of the original number of triangles). The actual reduction may be less depending on triangulation and topological constraints.

virtual void vtkQuadricDecimation::SetAttributeErrorMetric ( int ) [virtual]

Decide whether to include data attributes in the error metric. If off, then only geometric error is used to control the decimation. By default the attribute errors are off.

virtual int vtkQuadricDecimation::GetAttributeErrorMetric ( ) [virtual]

Decide whether to include data attributes in the error metric. If off, then only geometric error is used to control the decimation. By default the attribute errors are off.

virtual void vtkQuadricDecimation::AttributeErrorMetricOn ( ) [virtual]

Decide whether to include data attributes in the error metric. If off, then only geometric error is used to control the decimation. By default the attribute errors are off.

virtual void vtkQuadricDecimation::AttributeErrorMetricOff ( ) [virtual]

Decide whether to include data attributes in the error metric. If off, then only geometric error is used to control the decimation. By default the attribute errors are off.

virtual void vtkQuadricDecimation::SetScalarsAttribute ( int ) [virtual]