# vtkQuadricDecimation Class Reference

`#include <vtkQuadricDecimation.h>`

Inheritance diagram for vtkQuadricDecimation: [legend]
Collaboration diagram for vtkQuadricDecimation: [legend]
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.
virtual void SetTargetReduction (double)
virtual double GetTargetReduction ()
static vtkQuadricDecimationNew ()

## 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 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 vtkQuadricDecimationSafeDownCast (vtkObject *o)

## 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 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, const double t1, const double t2, const double *x)
void ComputeNumberOfComponents (void)
void GetAttributeComponents ()
void AddQuadric (vtkIdType oldPtId, vtkIdType newPtId)
double ComputeCost (vtkIdType edgeId, double *x)
double ComputeCost2 (vtkIdType edgeId, double *x)
void UpdateEdgeData (vtkIdType ptoId, vtkIdType pt1Id)
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
vtkEdgeTableEdges
vtkIdListEndPoint1List
vtkIdListEndPoint2List
vtkPriorityQueueEdgeCosts
vtkDoubleArrayTargetPoints
int NumberOfComponents
vtkPolyDataMesh
ErrorQuadricErrorQuadrics
int AttributeComponents 
double AttributeScale 
vtkIdListCollapseCellIds
double * TempX
double * TempQuad
double * TempB
double ** TempA
double * TempData

## Classes

struct  ErrorQuadric

## Member Typedef Documentation

 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 * type ) ` [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 vtkPolyDataAlgorithm.

 virtual int vtkQuadricDecimation::IsA ( const char * type ) ` [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 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]`
 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. 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]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual int vtkQuadricDecimation::GetScalarsAttribute ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::ScalarsAttributeOn ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::ScalarsAttributeOff ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::SetVectorsAttribute ( int ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual int vtkQuadricDecimation::GetVectorsAttribute ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::VectorsAttributeOn ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::VectorsAttributeOff ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::SetNormalsAttribute ( int ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual int vtkQuadricDecimation::GetNormalsAttribute ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::NormalsAttributeOn ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::NormalsAttributeOff ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::SetTCoordsAttribute ( int ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual int vtkQuadricDecimation::GetTCoordsAttribute ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::TCoordsAttributeOn ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::TCoordsAttributeOff ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::SetTensorsAttribute ( int ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual int vtkQuadricDecimation::GetTensorsAttribute ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::TensorsAttributeOn ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::TensorsAttributeOff ( ) ` [virtual]`
 If attribute errors are to be included in the metric (i.e., AttributeErrorMetric is on), then the following flags control which attributes are to be included in the error calculation. By default all of these are on.

 virtual void vtkQuadricDecimation::SetScalarsWeight ( double ) ` [virtual]`
 Set/Get the scaling weight contribution of the attribute. These values are used to weight the contribution of the attributes towards the error metric.

 virtual void vtkQuadricDecimation::SetVectorsWeight ( double ) ` [virtual]`
 Set/Get the scaling weight contribution of the attribute. These values are used to weight the contribution of the attributes towards the error metric.

 virtual void vtkQuadricDecimation::SetNormalsWeight ( double ) ` [virtual]`
 Set/Get the scaling weight contribution of the attribute. These values are used to weight the contribution of the attributes towards the error metric.

 virtual void vtkQuadricDecimation::SetTCoordsWeight ( double ) ` [virtual]`
 Set/Get the scaling weight contribution of the attribute. These values are used to weight the contribution of the attributes towards the error metric.

 virtual void vtkQuadricDecimation::SetTensorsWeight ( double ) ` [virtual]`
 Set/Get the scaling weight contribution of the attribute. These values are used to weight the contribution of the attributes towards the error metric.

 virtual double vtkQuadricDecimation::GetScalarsWeight ( ) ` [virtual]`
 Set/Get the scaling weight contribution of the attribute. These values are used to weight the contribution of the attributes towards the error metric.

 virtual double vtkQuadricDecimation::GetVectorsWeight ( ) ` [virtual]`
 Set/Get the scaling weight contribution of the attribute. These values are used to weight the contribution of the attributes towards the error metric.

 virtual double vtkQuadricDecimation::GetNormalsWeight ( ) ` [virtual]`
 Set/Get the scaling weight contribution of the attribute. These values are used to weight the contribution of the attributes towards the error metric.

 virtual double vtkQuadricDecimation::GetTCoordsWeight ( ) ` [virtual]`
 Set/Get the scaling weight contribution of the attribute. These values are used to weight the contribution of the attributes towards the error metric.

 virtual double vtkQuadricDecimation::GetTensorsWeight ( ) ` [virtual]`
 Set/Get the scaling weight contribution of the attribute. These values are used to weight the contribution of the attributes towards the error metric.

 virtual double vtkQuadricDecimation::GetActualReduction ( ) ` [virtual]`
 Get the actual reduction. This value is only valid after the filter has executed.

 int vtkQuadricDecimation::RequestData ( vtkInformation * , vtkInformationVector ** , vtkInformationVector * ) ` [protected, virtual]`
 This is called by the superclass. This is the method you should override. Reimplemented from vtkPolyDataAlgorithm.

 int vtkQuadricDecimation::CollapseEdge ( vtkIdType pt0Id, vtkIdType pt1Id ) ` [protected]`
 Do the dirty work of eliminating the edge; return the number of triangles deleted.

 void vtkQuadricDecimation::InitializeQuadrics ( vtkIdType numPts ) ` [protected]`
 Compute quadric for all vertices

 void vtkQuadricDecimation::AddBoundaryConstraints ( void ) ` [protected]`
 Free boundary edges are weighted

 void vtkQuadricDecimation::ComputeQuadric ( vtkIdType pointId ) ` [protected]`
 Compute quadric for this vertex.

 void vtkQuadricDecimation::AddQuadric ( vtkIdType oldPtId, vtkIdType newPtId ) ` [protected]`
 Add the quadrics for these 2 points since the edge between them has been collapsed.

 double vtkQuadricDecimation::ComputeCost ( vtkIdType edgeId, double * x ) ` [protected]`
 Compute cost for contracting this edge and the point that gives us this cost.

 double vtkQuadricDecimation::ComputeCost2 ( vtkIdType edgeId, double * x ) ` [protected]`
 Add the quadrics for these 2 points since the edge between them has been collapsed.

 void vtkQuadricDecimation::FindAffectedEdges ( vtkIdType p1Id, vtkIdType p2Id, vtkIdList * edges ) ` [protected]`
 Find all edges that will have an endpoint change ids because of an edge collapse. p1Id and p2Id are the endpoints of the edge. p2Id is the pointId being removed.

 vtkIdType vtkQuadricDecimation::GetEdgeCellId ( vtkIdType p1Id, vtkIdType p2Id ) ` [protected]`
 Find a cell that uses this edge.

 int vtkQuadricDecimation::IsGoodPlacement ( vtkIdType pt0Id, vtkIdType pt1Id, const double * x ) ` [protected]`

 int vtkQuadricDecimation::TrianglePlaneCheck ( const double t0, const double t1, const double t2, const double * x ) ` [protected]`

 void vtkQuadricDecimation::ComputeNumberOfComponents ( void ) ` [protected]`

 void vtkQuadricDecimation::UpdateEdgeData ( vtkIdType ptoId, vtkIdType pt1Id ) ` [protected]`

 void vtkQuadricDecimation::SetPointAttributeArray ( vtkIdType ptId, const double * x ) ` [protected]`
 Helper function to set and get the point and it's attributes as an array

 void vtkQuadricDecimation::GetPointAttributeArray ( vtkIdType ptId, double * x ) ` [protected]`

 void vtkQuadricDecimation::GetAttributeComponents ( ) ` [protected]`
 Find out how many components there are for each attribute for this poly data.

## Member Data Documentation

 double vtkQuadricDecimation::TargetReduction` [protected]`
 Definition at line 192 of file vtkQuadricDecimation.h.

 double vtkQuadricDecimation::ActualReduction` [protected]`
 Definition at line 193 of file vtkQuadricDecimation.h.

 int vtkQuadricDecimation::AttributeErrorMetric` [protected]`
 Definition at line 194 of file vtkQuadricDecimation.h.

 int vtkQuadricDecimation::ScalarsAttribute` [protected]`
 Definition at line 196 of file vtkQuadricDecimation.h.

 int vtkQuadricDecimation::VectorsAttribute` [protected]`
 Definition at line 197 of file vtkQuadricDecimation.h.

 int vtkQuadricDecimation::NormalsAttribute` [protected]`
 Definition at line 198 of file vtkQuadricDecimation.h.

 int vtkQuadricDecimation::TCoordsAttribute` [protected]`
 Definition at line 199 of file vtkQuadricDecimation.h.

 int vtkQuadricDecimation::TensorsAttribute` [protected]`
 Definition at line 200 of file vtkQuadricDecimation.h.

 double vtkQuadricDecimation::ScalarsWeight` [protected]`
 Definition at line 202 of file vtkQuadricDecimation.h.

 double vtkQuadricDecimation::VectorsWeight` [protected]`
 Definition at line 203 of file vtkQuadricDecimation.h.

 double vtkQuadricDecimation::NormalsWeight` [protected]`
 Definition at line 204 of file vtkQuadricDecimation.h.

 double vtkQuadricDecimation::TCoordsWeight` [protected]`
 Definition at line 205 of file vtkQuadricDecimation.h.

 double vtkQuadricDecimation::TensorsWeight` [protected]`
 Definition at line 206 of file vtkQuadricDecimation.h.

 int vtkQuadricDecimation::NumberOfEdgeCollapses` [protected]`
 Definition at line 208 of file vtkQuadricDecimation.h.

 vtkEdgeTable* vtkQuadricDecimation::Edges` [protected]`
 Definition at line 209 of file vtkQuadricDecimation.h.

 vtkIdList* vtkQuadricDecimation::EndPoint1List` [protected]`
 Definition at line 210 of file vtkQuadricDecimation.h.

 vtkIdList* vtkQuadricDecimation::EndPoint2List` [protected]`
 Definition at line 211 of file vtkQuadricDecimation.h.

 vtkPriorityQueue* vtkQuadricDecimation::EdgeCosts` [protected]`
 Definition at line 212 of file vtkQuadricDecimation.h.

 vtkDoubleArray* vtkQuadricDecimation::TargetPoints` [protected]`
 Definition at line 213 of file vtkQuadricDecimation.h.

 int vtkQuadricDecimation::NumberOfComponents` [protected]`
 Definition at line 214 of file vtkQuadricDecimation.h.

 vtkPolyData* vtkQuadricDecimation::Mesh` [protected]`
 Definition at line 215 of file vtkQuadricDecimation.h.

 ErrorQuadric* vtkQuadricDecimation::ErrorQuadrics` [protected]`
 Definition at line 224 of file vtkQuadricDecimation.h.

 int vtkQuadricDecimation::AttributeComponents` [protected]`
 Definition at line 225 of file vtkQuadricDecimation.h.

 double vtkQuadricDecimation::AttributeScale` [protected]`
 Definition at line 226 of file vtkQuadricDecimation.h.

 vtkIdList* vtkQuadricDecimation::CollapseCellIds` [protected]`
 Definition at line 229 of file vtkQuadricDecimation.h.

 double* vtkQuadricDecimation::TempX` [protected]`
 Definition at line 230 of file vtkQuadricDecimation.h.

 double* vtkQuadricDecimation::TempQuad` [protected]`
 Definition at line 231 of file vtkQuadricDecimation.h.

 double* vtkQuadricDecimation::TempB` [protected]`
 Definition at line 232 of file vtkQuadricDecimation.h.

 double** vtkQuadricDecimation::TempA` [protected]`
 Definition at line 233 of file vtkQuadricDecimation.h.

 double* vtkQuadricDecimation::TempData` [protected]`
 Definition at line 234 of file vtkQuadricDecimation.h.

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

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