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vtkDecimatePro Class Reference

reduce the number of triangles in a mesh. More...

#include <vtkDecimatePro.h>

Inheritance diagram for vtkDecimatePro:

Inheritance graph
Collaboration diagram for vtkDecimatePro:

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List of all members.

Public Methods

virtual const char * GetClassName ()
virtual int IsA (const char *type)
void PrintSelf (ostream &os, vtkIndent indent)
virtual void SetTargetReduction (float)
virtual float GetTargetReduction ()
virtual void SetPreserveTopology (int)
virtual int GetPreserveTopology ()
virtual void PreserveTopologyOn ()
virtual void PreserveTopologyOff ()
virtual void SetFeatureAngle (float)
virtual float GetFeatureAngle ()
virtual void SetSplitting (int)
virtual int GetSplitting ()
virtual void SplittingOn ()
virtual void SplittingOff ()
virtual void SetSplitAngle (float)
virtual float GetSplitAngle ()
virtual void SetPreSplitMesh (int)
virtual int GetPreSplitMesh ()
virtual void PreSplitMeshOn ()
virtual void PreSplitMeshOff ()
virtual void SetMaximumError (float)
virtual float GetMaximumError ()
virtual void SetAccumulateError (int)
virtual int GetAccumulateError ()
virtual void AccumulateErrorOn ()
virtual void AccumulateErrorOff ()
virtual void SetErrorIsAbsolute (int)
virtual int GetErrorIsAbsolute ()
virtual void SetAbsoluteError (float)
virtual float GetAbsoluteError ()
virtual void SetBoundaryVertexDeletion (int)
virtual int GetBoundaryVertexDeletion ()
virtual void BoundaryVertexDeletionOn ()
virtual void BoundaryVertexDeletionOff ()
virtual void SetDegree (int)
virtual int GetDegree ()
virtual void SetInflectionPointRatio (float)
virtual float GetInflectionPointRatio ()
int GetNumberOfInflectionPoints ()
void GetInflectionPoints (float *inflectionPoints)
float * GetInflectionPoints ()

Static Public Methods

int IsTypeOf (const char *type)
vtkDecimatePro * SafeDownCast (vtkObject *o)
vtkDecimatePro * New ()

Protected Methods

 vtkDecimatePro ()
 ~vtkDecimatePro ()
 vtkDecimatePro (const vtkDecimatePro &)
void operator= (const vtkDecimatePro &)
void Execute ()
void SplitMesh ()
int EvaluateVertex (int ptId, unsigned short int numTris, int *tris, int fedges[2])
int FindSplit (int type, int fedges[2], int &pt1, int &pt2, vtkIdList *CollapseTris)
int IsValidSplit (int index)
void SplitLoop (int fedges[2], int &n1, int *l1, int &n2, int *l2)
void SplitVertex (int ptId, int type, unsigned short int numTris, int *tris, int insert)
int CollapseEdge (int type, int ptId, int collapseId, int pt1, int pt2, vtkIdList *CollapseTris)
void DistributeError (float error)

Protected Attributes

float TargetReduction
float FeatureAngle
float MaximumError
float AbsoluteError
int ErrorIsAbsolute
int AccumulateError
float SplitAngle
int Splitting
int PreSplitMesh
int BoundaryVertexDeletion
int PreserveTopology
int Degree
float InflectionPointRatio

Detailed Description

reduce the number of triangles in a mesh.

2000/12/10 20:08:35

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

The implementation of vtkDecimatePro is similar to the algorithm originally described in "Decimation of Triangle Meshes", Proc Siggraph `92, with three major differences. First, this algorithm does not necessarily preserve the topology of the mesh. Second, it is guaranteed to give the a mesh reduction factor specified by the user (as long as certain constraints are not set - see Caveats). Third, it is set up generate progressive meshes, that is a stream of operations that can be easily transmitted and incrementally updated (see Hugues Hoppe's Siggraph '96 paper on progressive meshes).

The algorithm proceeds as follows. Each vertex in the mesh is classified and inserted into a priority queue. The priority is based on the error to delete the vertex and retriangulate the hole. Vertices that cannot be deleted or triangulated (at this point in the algorithm) are skipped. Then, each vertex in the priority queue is processed (i.e., deleted followed by hole triangulation using edge collapse). This continues until the priority queue is empty. Next, all remaining vertices are processed, and the mesh is split into separate pieces along sharp edges or at non-manifold attachment points and reinserted into the priority queue. Again, the priority queue is processed until empty. If the desired reduction is still not achieved, the remaining vertices are split as necessary (in a recursive fashion) so that it is possible to eliminate every triangle as necessary.

To use this object, at a minimum you need to specify the ivar TargetReduction. The algorithm is guaranteed to generate a reduced mesh at this level as long as the following four conditions are met: 1) topology modification is allowed (i.e., the ivar PreserveTopology is off); 2) mesh splitting is enabled (i.e., the ivar Splitting is on); 3) the algorithm is allowed to modify the boundary of the mesh (i.e., the ivar BoundaryVertexDeletion is on); and 4) the maximum allowable error (i.e., the ivar MaximumError) is set to VTK_LARGE_FLOAT. Other important parameters to adjust include the FeatureAngle and SplitAngle ivars, since these can impact the quality of the final mesh. Also, you can set the ivar AccumulateError to force incremental error update and distribution to surrounding vertices as each vertex is deleted. The accumulated error is a conservative global error bounds and decimation error, but requires additional memory and time to compute.

To guarantee a given level of reduction, the ivar PreserveTopology must be off; the ivar Splitting is on; the ivar BoundaryVertexDeletion is on; and the ivar MaximumError is set to VTK_LARGE_FLOAT.
If PreserveTopology is off, and SplitEdges is off; the mesh topology may be modified by closing holes.
Once mesh splitting begins, the feature angle is set to the split angle.
See also:
vtkDecimate vtkQuadricClustering vtkQuadricDecimation
vtkDecimatePro (examples)

Definition at line 181 of file vtkDecimatePro.h.

Constructor & Destructor Documentation

vtkDecimatePro::vtkDecimatePro   [protected]

vtkDecimatePro::~vtkDecimatePro   [protected]

vtkDecimatePro::vtkDecimatePro const vtkDecimatePro &    [inline, protected]

Definition at line 313 of file vtkDecimatePro.h.

Member Function Documentation

virtual const char* vtkDecimatePro::GetClassName   [virtual]

Return the class name as a string. This method is defined in all subclasses of vtkObject with the vtkTypeMacro found in vtkSetGet.h.

Reimplemented from vtkPolyDataToPolyDataFilter.

int vtkDecimatePro::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 vtkTypeMacro found in vtkSetGet.h.

Reimplemented from vtkPolyDataToPolyDataFilter.

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

Reimplemented from vtkPolyDataToPolyDataFilter.

vtkDecimatePro* vtkDecimatePro::SafeDownCast vtkObject   o [static]

Will cast the supplied object to vtkObject* is this is a safe operation (i.e., a safe downcast); otherwise NULL is returned. This method is defined in all subclasses of vtkObject with the vtkTypeMacro found in vtkSetGet.h.

Reimplemented from vtkPolyDataToPolyDataFilter.

void vtkDecimatePro::PrintSelf ostream &    os,
vtkIndent    indent

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 vtkSource.

vtkDecimatePro* vtkDecimatePro::New   [static]

Create object with specified reduction of 90% and feature angle of 15 degrees. Edge splitting is on, defer splitting is on, and the split angle is 75 degrees. Topology preservation is off, delete boundary vertices is on, and the maximum error is set to VTK_LARGE_FLOAT. The inflection point ratio is 10 and the vertex degree is 25. Error accumulation is turned off.

Reimplemented from vtkPolyDataSource.

virtual void vtkDecimatePro::SetTargetReduction float    [virtual]

Specify the desired reduction in the total number of polygons. Because of various constraints, this level of reduction may not be realized. If you want to guarantee a particular reduction, you must turn off PreserveTopology and BoundaryVertexDeletion, turn on SplitEdges, and set the MaximumError to VTK_LARGE_FLOAT (these ivars are initialized this way when the object is instantiated).

virtual float vtkDecimatePro::GetTargetReduction   [virtual]

virtual void vtkDecimatePro::SetPreserveTopology int    [virtual]

Turn on/off whether to preserve the topology of the original mesh. If on, mesh splitting and hole elimination will not occur. This may limit the maximum reduction that may be achieved.

virtual int vtkDecimatePro::GetPreserveTopology   [virtual]

virtual void vtkDecimatePro::PreserveTopologyOn   [virtual]

virtual void vtkDecimatePro::PreserveTopologyOff   [virtual]

virtual void vtkDecimatePro::SetFeatureAngle float    [virtual]

Specify the mesh feature angle. This angle is used to define what an edge is (i.e., if the surface normal between two adjacent triangles is >= FeatureAngle, an edge exists).

virtual float vtkDecimatePro::GetFeatureAngle   [virtual]

virtual void vtkDecimatePro::SetSplitting int    [virtual]

Turn on/off the splitting of the mesh at corners, along edges, at non-manifold points, or anywhere else a split is required. Turning splitting off will better preserve the original topology of the mesh, but you may not obtain the requested reduction.

virtual int vtkDecimatePro::GetSplitting   [virtual]

virtual void vtkDecimatePro::SplittingOn   [virtual]

virtual void vtkDecimatePro::SplittingOff   [virtual]

virtual void vtkDecimatePro::SetSplitAngle float    [virtual]

Specify the mesh split angle. This angle is used to control the splitting of the mesh. A split line exists when the surface normals between two edge connected triangles are >= SplitAngle.

virtual float vtkDecimatePro::GetSplitAngle   [virtual]

virtual void vtkDecimatePro::SetPreSplitMesh int    [virtual]

In some cases you may wish to split the mesh prior to algorithm execution. This separates the mesh into semi-planar patches, which are disconnected from each other. This can give superior results in some cases. If the ivar PreSplitMesh ivar is enabled, the mesh is split with the specified SplitAngle. Otherwise mesh splitting is deferred as long as possible.

virtual int vtkDecimatePro::GetPreSplitMesh   [virtual]

virtual void vtkDecimatePro::PreSplitMeshOn   [virtual]

virtual void vtkDecimatePro::PreSplitMeshOff   [virtual]

virtual void vtkDecimatePro::SetMaximumError float    [virtual]

Set the largest decimation error that is allowed during the decimation process. This may limit the maximum reduction that may be achieved. The maximum error is specified as a fraction of the maximum length of the input data bounding box.

virtual float vtkDecimatePro::GetMaximumError   [virtual]

virtual void vtkDecimatePro::SetAccumulateError int    [virtual]

The computed error can either be computed directly from the mesh or the error may be accumulated as the mesh is modified. If the error is accumulated, then it represents a global error bounds, and the ivar MaximumError becomes a global bounds on mesh error. Accumulating the error requires extra memory proportional to the number of vertices in the mesh. If AccumulateError is off, then the error is not accumulated.

virtual int vtkDecimatePro::GetAccumulateError   [virtual]

virtual void vtkDecimatePro::AccumulateErrorOn   [virtual]

virtual void vtkDecimatePro::AccumulateErrorOff   [virtual]

virtual void vtkDecimatePro::SetErrorIsAbsolute int    [virtual]

The MaximumError is normally defined as a fraction of the dataset bounding diagonal. By setting ErrorIsAbsolute to 1, the error is instead defined as that specified by AbsoluteError. By default ErrorIsAbsolute=0.

virtual int vtkDecimatePro::GetErrorIsAbsolute   [virtual]

virtual void vtkDecimatePro::SetAbsoluteError float    [virtual]

Same as MaximumError, but to be used when ErrorIsAbsolute is 1

virtual float vtkDecimatePro::GetAbsoluteError   [virtual]

virtual void vtkDecimatePro::SetBoundaryVertexDeletion int    [virtual]

Turn on/off the deletion of vertices on the boundary of a mesh. This may limit the maximum reduction that may be achieved.

virtual int vtkDecimatePro::GetBoundaryVertexDeletion   [virtual]

virtual void vtkDecimatePro::BoundaryVertexDeletionOn   [virtual]

virtual void vtkDecimatePro::BoundaryVertexDeletionOff   [virtual]

virtual void vtkDecimatePro::SetDegree int    [virtual]

If the number of triangles connected to a vertex exceeds "Degree", then the vertex will be split. (NOTE: the complexity of the triangulation algorithm is proportional to Degree^2. Setting degree small can improve the performance of the algorithm.)

virtual int vtkDecimatePro::GetDegree   [virtual]

virtual void vtkDecimatePro::SetInflectionPointRatio float    [virtual]

Specify the inflection point ratio. An inflection point occurs when the ratio of reduction error between two iterations is greater than or equal to the InflectionPointRatio.

virtual float vtkDecimatePro::GetInflectionPointRatio   [virtual]

int vtkDecimatePro::GetNumberOfInflectionPoints  

Get the number of inflection points. Only returns a valid value after the filter has executed. The values in the list are mesh reduction values at each inflection point. Note: the first inflection point always occurs right before non-planar triangles are decimated (i.e., as the error becomes non-zero).

void vtkDecimatePro::GetInflectionPoints float *    inflectionPoints

Get a list of inflection points. These are float values 0 < r <= 1.0 corresponding to reduction level, and there are a total of NumberOfInflectionPoints() values. You must provide an array (of the correct size) into which the inflection points are written.

float* vtkDecimatePro::GetInflectionPoints  

Get a list of inflection points. These are float values 0 < r <= 1.0 corresponding to reduction level, and there are a total of NumberOfInflectionPoints() values. You must provide an array (of the correct size) into which the inflection points are written. This method returns a pointer to a list of inflection points.

void vtkDecimatePro::operator= const vtkDecimatePro &    [inline, protected]

Definition at line 314 of file vtkDecimatePro.h.

void vtkDecimatePro::Execute   [protected, virtual]

Reimplemented from vtkSource.

void vtkDecimatePro::SplitMesh   [protected]

int vtkDecimatePro::EvaluateVertex int    ptId,
unsigned short int    numTris,
int *    tris,
int    fedges[2]

int vtkDecimatePro::FindSplit int    type,
int    fedges[2],
int &    pt1,
int &    pt2,
vtkIdList   CollapseTris

int vtkDecimatePro::IsValidSplit int    index [protected]

void vtkDecimatePro::SplitLoop int    fedges[2],
int &    n1,
int *    l1,
int &    n2,
int *    l2

void vtkDecimatePro::SplitVertex int    ptId,
int    type,
unsigned short int    numTris,
int *    tris,
int    insert

int vtkDecimatePro::CollapseEdge int    type,
int    ptId,
int    collapseId,
int    pt1,
int    pt2,
vtkIdList   CollapseTris

void vtkDecimatePro::DistributeError float    error [protected]

Member Data Documentation

float vtkDecimatePro::TargetReduction [protected]

Definition at line 318 of file vtkDecimatePro.h.

float vtkDecimatePro::FeatureAngle [protected]

Definition at line 319 of file vtkDecimatePro.h.

float vtkDecimatePro::MaximumError [protected]

Definition at line 320 of file vtkDecimatePro.h.

float vtkDecimatePro::AbsoluteError [protected]

Definition at line 321 of file vtkDecimatePro.h.

int vtkDecimatePro::ErrorIsAbsolute [protected]

Definition at line 322 of file vtkDecimatePro.h.

int vtkDecimatePro::AccumulateError [protected]

Definition at line 323 of file vtkDecimatePro.h.

float vtkDecimatePro::SplitAngle [protected]

Definition at line 324 of file vtkDecimatePro.h.

int vtkDecimatePro::Splitting [protected]

Definition at line 325 of file vtkDecimatePro.h.

int vtkDecimatePro::PreSplitMesh [protected]

Definition at line 326 of file vtkDecimatePro.h.

int vtkDecimatePro::BoundaryVertexDeletion [protected]

Definition at line 327 of file vtkDecimatePro.h.

int vtkDecimatePro::PreserveTopology [protected]

Definition at line 328 of file vtkDecimatePro.h.

int vtkDecimatePro::Degree [protected]

Definition at line 329 of file vtkDecimatePro.h.

float vtkDecimatePro::InflectionPointRatio [protected]

Definition at line 330 of file vtkDecimatePro.h.

vtkFloatArray* vtkDecimatePro::InflectionPoints [protected]

Definition at line 331 of file vtkDecimatePro.h.

vtkIdList* vtkDecimatePro::Neighbors [protected]

Definition at line 334 of file vtkDecimatePro.h.

vtkPriorityQueue* vtkDecimatePro::EdgeLengths [protected]

Definition at line 335 of file vtkDecimatePro.h.

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