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vtkDecimatePro Class Reference
reduce the number of triangles in a mesh.
More...
#include <vtkDecimatePro.h>
Inheritance diagram for vtkDecimatePro:
[legend]Collaboration diagram for vtkDecimatePro:
[legend]List of all members.
Public Methods 
virtual const char *  GetClassName () 
virtual int  IsA (const char *type) 
void  PrintSelf (ostream &os, vtkIndent indent) 
vtkIdType  GetNumberOfInflectionPoints () 
void  GetInflectionPoints (float *inflectionPoints) 
float *  GetInflectionPoints () 

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 () 
Static Public Methods 
int  IsTypeOf (const char *type) 
vtkDecimatePro *  SafeDownCast (vtkObject *o) 
vtkDecimatePro *  New () 
Protected Methods 
 vtkDecimatePro () 
 ~vtkDecimatePro () 
void  Execute () 
void  SplitMesh () 
int  EvaluateVertex (vtkIdType ptId, unsigned short int numTris, vtkIdType *tris, vtkIdType fedges[2]) 
vtkIdType  FindSplit (int type, vtkIdType fedges[2], vtkIdType &pt1, vtkIdType &pt2, vtkIdList *CollapseTris) 
int  IsValidSplit (int index) 
void  SplitLoop (vtkIdType fedges[2], vtkIdType &n1, vtkIdType *l1, vtkIdType &n2, vtkIdType *l2) 
void  SplitVertex (vtkIdType ptId, int type, unsigned short int numTris, vtkIdType *tris, int insert) 
int  CollapseEdge (int type, vtkIdType ptId, vtkIdType collapseId, vtkIdType pt1, vtkIdType 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 
vtkFloatArray *  InflectionPoints 
vtkIdList *  Neighbors 
vtkPriorityQueue *  EdgeLengths 
Detailed Description
reduce the number of triangles in a mesh.

Date:

2001/11/13 14:13:49

Revision:

1.49
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 nonmanifold 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.

Warning:

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.

Warning:

If PreserveTopology is off, and SplitEdges is off; the mesh topology may be modified by closing holes.

Warning:

Once mesh splitting begins, the feature angle is set to the split angle.

See also:

vtkDecimate vtkQuadricClustering vtkQuadricDecimation

Examples:

vtkDecimatePro (Examples)

Tests:

vtkDecimatePro (Tests)
Definition at line 185 of file vtkDecimatePro.h.
Constructor & Destructor Documentation
vtkDecimatePro::vtkDecimatePro 
( 

) 
[protected] 

vtkDecimatePro::~vtkDecimatePro 
( 

) 
[protected] 

Member Function Documentation
virtual const char* vtkDecimatePro::GetClassName 
( 

) 
[virtual] 

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] 

void vtkDecimatePro::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 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] 


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 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] 


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 void vtkDecimatePro::PreserveTopologyOn 
( 

) 
[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 void vtkDecimatePro::PreserveTopologyOff 
( 

) 
[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 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] 


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 void vtkDecimatePro::SetSplitting 
( 
int 

) 
[virtual] 


Turn on/off the splitting of the mesh at corners, along edges, at nonmanifold 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] 


Turn on/off the splitting of the mesh at corners, along edges, at nonmanifold 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 void vtkDecimatePro::SplittingOn 
( 

) 
[virtual] 


Turn on/off the splitting of the mesh at corners, along edges, at nonmanifold 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 void vtkDecimatePro::SplittingOff 
( 

) 
[virtual] 


Turn on/off the splitting of the mesh at corners, along edges, at nonmanifold 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 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] 


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 void vtkDecimatePro::SetPreSplitMesh 
( 
int 

) 
[virtual] 


In some cases you may wish to split the mesh prior to algorithm execution. This separates the mesh into semiplanar 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] 


In some cases you may wish to split the mesh prior to algorithm execution. This separates the mesh into semiplanar 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 void vtkDecimatePro::PreSplitMeshOn 
( 

) 
[virtual] 


In some cases you may wish to split the mesh prior to algorithm execution. This separates the mesh into semiplanar 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 void vtkDecimatePro::PreSplitMeshOff 
( 

) 
[virtual] 


In some cases you may wish to split the mesh prior to algorithm execution. This separates the mesh into semiplanar 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 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] 


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 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] 


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 void vtkDecimatePro::AccumulateErrorOn 
( 

) 
[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 void vtkDecimatePro::AccumulateErrorOff 
( 

) 
[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 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] 


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 void vtkDecimatePro::SetAbsoluteError 
( 
float 

) 
[virtual] 


Same as MaximumError, but to be used when ErrorIsAbsolute is 1 
virtual float vtkDecimatePro::GetAbsoluteError 
( 

) 
[virtual] 


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


Turn on/off the deletion of vertices on the boundary of a mesh. This may limit the maximum reduction that may be achieved. 
virtual void vtkDecimatePro::BoundaryVertexDeletionOn 
( 

) 
[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 void vtkDecimatePro::BoundaryVertexDeletionOff 
( 

) 
[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 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] 


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 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] 


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. 
vtkIdType 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 nonplanar triangles are decimated (i.e., as the error becomes nonzero). 
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::Execute 
( 

) 
[protected, virtual] 


This method is the old style execute method
Reimplemented from vtkSource. 
void vtkDecimatePro::SplitMesh 
( 

) 
[protected] 

int vtkDecimatePro::IsValidSplit 
( 
int 
index 
) 
[protected] 

void vtkDecimatePro::SplitVertex 
( 
vtkIdType 
ptId, 


int 
type, 


unsigned short int 
numTris, 


vtkIdType * 
tris, 


int 
insert 

) 
[protected] 

void vtkDecimatePro::DistributeError 
( 
float 
error 
) 
[protected] 

Member Data Documentation
float vtkDecimatePro::TargetReduction [protected]


float vtkDecimatePro::FeatureAngle [protected]


float vtkDecimatePro::MaximumError [protected]


float vtkDecimatePro::AbsoluteError [protected]


int vtkDecimatePro::ErrorIsAbsolute [protected]


int vtkDecimatePro::AccumulateError [protected]


float vtkDecimatePro::SplitAngle [protected]


int vtkDecimatePro::Splitting [protected]


int vtkDecimatePro::PreSplitMesh [protected]


int vtkDecimatePro::BoundaryVertexDeletion [protected]


int vtkDecimatePro::PreserveTopology [protected]


int vtkDecimatePro::Degree [protected]


float vtkDecimatePro::InflectionPointRatio [protected]


vtkIdList* vtkDecimatePro::Neighbors [protected]


The documentation for this class was generated from the following file:
Generated on Thu Mar 28 14:28:50 2002 for VTK by
1.2.11.1 written by Dimitri van Heesch,
© 19972001