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259 lines
9.9 KiB
C++
259 lines
9.9 KiB
C++
/*=========================================================================
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Program: Visualization Toolkit
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Module: vtkGreedyTerrainDecimation.h
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Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
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All rights reserved.
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See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
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This software is distributed WITHOUT ANY WARRANTY; without even
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the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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PURPOSE. See the above copyright notice for more information.
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=========================================================================*/
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/**
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* @class vtkGreedyTerrainDecimation
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* @brief reduce height field (represented as image) to reduced TIN
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*
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* vtkGreedyTerrainDecimation approximates a height field with a triangle
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* mesh (triangulated irregular network - TIN) using a greedy insertion
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* algorithm similar to that described by Garland and Heckbert in their paper
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* "Fast Polygonal Approximations of Terrain and Height Fields" (Technical
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* Report CMU-CS-95-181). The input to the filter is a height field
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* (represented by a image whose scalar values are height) and the output of
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* the filter is polygonal data consisting of triangles. The number of
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* triangles in the output is reduced in number as compared to a naive
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* tessellation of the input height field. This filter copies point data
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* from the input to the output for those points present in the output.
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*
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* An brief description of the algorithm is as follows. The algorithm uses a
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* top-down decimation approach that initially represents the height field
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* with two triangles (whose vertices are at the four corners of the
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* image). These two triangles form a Delaunay triangulation. In an iterative
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* fashion, the point in the image with the greatest error (as compared to
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* the original height field) is injected into the triangulation. (Note that
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* the single point with the greatest error per triangle is identified and
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* placed into a priority queue. As the triangulation is modified, the errors
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* from the deleted triangles are removed from the queue, error values from
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* the new triangles are added.) The point whose error is at the top of the
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* queue is added to the triangulaion modifying it using the standard
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* incremental Delaunay point insertion (see vtkDelaunay2D) algorithm. Points
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* are repeatedly inserted until the appropriate (user-specified) error
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* criterion is met.
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*
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* To use this filter, set the input and specify the error measure to be
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* used. The error measure options are 1) the absolute number of triangles
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* to be produced; 2) a fractional reduction of the mesh (numTris/maxTris)
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* where maxTris is the largest possible number of triangles
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* 2*(dims[0]-1)*(dims[1]-1); 3) an absolute measure on error (maximum
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* difference in height field to reduced TIN); and 4) relative error (the
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* absolute error is normalized by the diagonal of the bounding box of the
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* height field).
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*
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* @warning
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* This algorithm requires the entire input dataset to be in memory, hence it
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* may not work for extremely large images. Invoking BoundaryVertexDeletionOff
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* will allow you to stitch together images with matching boundaries.
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*
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* @warning
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* The input height image is assumed to be positioned in the x-y plane so the
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* scalar value is the z-coordinate, height value.
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*
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* @sa
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* vtkDecimatePro vtkQuadricDecimation vtkQuadricClustering
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*/
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#ifndef vtkGreedyTerrainDecimation_h
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#define vtkGreedyTerrainDecimation_h
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#include "vtkFiltersHybridModule.h" // For export macro
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#include "vtkPolyDataAlgorithm.h"
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class vtkPriorityQueue;
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class vtkDataArray;
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class vtkPointData;
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class vtkIdList;
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class vtkDoubleArray;
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class vtkFloatArray;
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//PIMPL Encapsulation for STL containers
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class vtkGreedyTerrainDecimationTerrainInfoType;
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class vtkGreedyTerrainDecimationPointInfoType;
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#define VTK_ERROR_NUMBER_OF_TRIANGLES 0
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#define VTK_ERROR_SPECIFIED_REDUCTION 1
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#define VTK_ERROR_ABSOLUTE 2
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#define VTK_ERROR_RELATIVE 3
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class VTKFILTERSHYBRID_EXPORT vtkGreedyTerrainDecimation : public vtkPolyDataAlgorithm
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{
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public:
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vtkTypeMacro(vtkGreedyTerrainDecimation,vtkPolyDataAlgorithm);
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void PrintSelf(ostream& os, vtkIndent indent);
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/**
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* Instantiate the class.
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*/
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static vtkGreedyTerrainDecimation* New();
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//@{
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/**
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* Specify how to terminate the algorithm: either as an absolute number of
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* triangles, a relative number of triangles (normalized by the full
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* resolution mesh), an absolute error (in the height field), or relative
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* error (normalized by the length of the diagonal of the image).
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*/
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vtkSetClampMacro(ErrorMeasure,int,VTK_ERROR_NUMBER_OF_TRIANGLES,VTK_ERROR_RELATIVE);
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vtkGetMacro(ErrorMeasure,int);
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void SetErrorMeasureToNumberOfTriangles()
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{this->SetErrorMeasure(VTK_ERROR_NUMBER_OF_TRIANGLES);}
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void SetErrorMeasureToSpecifiedReduction()
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{this->SetErrorMeasure(VTK_ERROR_SPECIFIED_REDUCTION);}
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void SetErrorMeasureToAbsoluteError()
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{this->SetErrorMeasure(VTK_ERROR_ABSOLUTE);}
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void SetErrorMeasureToRelativeError()
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{this->SetErrorMeasure(VTK_ERROR_RELATIVE);}
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//@}
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//@{
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/**
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* Specify the number of triangles to produce on output. (It is a
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* good idea to make sure this is less than a tessellated mesh
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* at full resolution.) You need to set this value only when
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* the error measure is set to NumberOfTriangles.
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*/
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vtkSetClampMacro(NumberOfTriangles,vtkIdType,2,VTK_ID_MAX);
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vtkGetMacro(NumberOfTriangles,vtkIdType);
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//@}
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//@{
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/**
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* Specify the reduction of the mesh (represented as a fraction). Note
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* that a value of 0.10 means a 10% reduction. You need to set this value
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* only when the error measure is set to SpecifiedReduction.
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*/
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vtkSetClampMacro(Reduction,double,0.0,1.0);
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vtkGetMacro(Reduction,double);
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//@}
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//@{
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/**
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* Specify the absolute error of the mesh; that is, the error in height
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* between the decimated mesh and the original height field. You need to
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* set this value only when the error measure is set to AbsoluteError.
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*/
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vtkSetClampMacro(AbsoluteError,double,0.0,VTK_DOUBLE_MAX);
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vtkGetMacro(AbsoluteError,double);
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//@}
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//@{
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/**
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* Specify the relative error of the mesh; that is, the error in height
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* between the decimated mesh and the original height field normalized by
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* the diagonal of the image. You need to set this value only when the
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* error measure is set to RelativeError.
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*/
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vtkSetClampMacro(RelativeError,double,0.0,VTK_DOUBLE_MAX);
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vtkGetMacro(RelativeError,double);
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//@}
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//@{
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/**
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* Turn on/off the deletion of vertices on the boundary of a mesh. This
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* may limit the maximum reduction that may be achieved.
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*/
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vtkSetMacro(BoundaryVertexDeletion,int);
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vtkGetMacro(BoundaryVertexDeletion,int);
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vtkBooleanMacro(BoundaryVertexDeletion,int);
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//@}
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//@{
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/**
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* Compute normals based on the input image. Off by default.
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*/
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vtkSetMacro(ComputeNormals, int);
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vtkGetMacro(ComputeNormals, int);
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vtkBooleanMacro(ComputeNormals, int);
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//@}
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protected:
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vtkGreedyTerrainDecimation();
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~vtkGreedyTerrainDecimation();
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virtual int RequestData(vtkInformation *, vtkInformationVector **, vtkInformationVector *);
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virtual int FillInputPortInformation(int port, vtkInformation *info);
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int ComputeNormals;
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vtkFloatArray* Normals;
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void ComputePointNormal(int i, int j, float n[3]);
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//ivars that the API addresses
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int ErrorMeasure;
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vtkIdType NumberOfTriangles;
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double Reduction;
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double AbsoluteError;
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double RelativeError;
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int BoundaryVertexDeletion; //Can we delete boundary vertices?
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//Used for convenience
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vtkPolyData *Mesh;
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vtkPointData *InputPD;
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vtkPointData *OutputPD;
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vtkDoubleArray *Points;
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vtkDataArray *Heights;
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vtkIdType CurrentPointId;
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double Tolerance;
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vtkIdList *Neighbors;
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int Dimensions[3];
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double Origin[3];
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double Spacing[3];
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vtkIdType MaximumNumberOfTriangles;
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double Length;
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//Bookeeping arrays
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vtkPriorityQueue *TerrainError; //errors for each pt in height field
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vtkGreedyTerrainDecimationTerrainInfoType *TerrainInfo; //owning triangle for each pt
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vtkGreedyTerrainDecimationPointInfoType *PointInfo; //map mesh pt id to input pt id
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//Make a guess at initial allocation
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void EstimateOutputSize(const vtkIdType numInputPts, vtkIdType &numPts, vtkIdType &numTris);
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//Returns non-zero if the error measure is satisfied.
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virtual int SatisfiesErrorMeasure(double error);
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//Insert all the boundary vertices into the TIN
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void InsertBoundaryVertices();
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//Insert a point into the triangulation; get a point from the triangulation
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vtkIdType AddPointToTriangulation(vtkIdType inputPtId);
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vtkIdType InsertNextPoint(vtkIdType inputPtId, double x[3]);
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double *GetPoint(vtkIdType id);
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void GetPoint(vtkIdType id, double x[3]);
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//Helper functions
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void GetTerrainPoint(int i, int j, double x[3]);
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void ComputeImageCoordinates(vtkIdType inputPtId, int ij[2]);
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int InCircle (double x[3], double x1[3], double x2[3], double x3[3]);
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vtkIdType FindTriangle(double x[3], vtkIdType ptIds[3], vtkIdType tri,
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double tol, vtkIdType nei[3], vtkIdList *neighbors, int& status);
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void CheckEdge(vtkIdType ptId, double x[3], vtkIdType p1, vtkIdType p2,
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vtkIdType tri, int depth);
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void UpdateTriangles(vtkIdType meshPtId); //update all points connected to this point
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void UpdateTriangle(vtkIdType triId, vtkIdType p1, vtkIdType p2, vtkIdType p3);
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void UpdateTriangle(vtkIdType triId, int ij1[2], int ij2[2], int ij3[2], double h[4]);
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int CharacterizeTriangle(int ij1[2], int ij2[2], int ij[3],
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int* &min, int* &max, int* &midL, int* &midR,
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int* &mid, int mid2[2], double h[3], double &hMin, double &hMax,
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double &hL, double &hR);
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private:
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vtkGreedyTerrainDecimation(const vtkGreedyTerrainDecimation&) VTK_DELETE_FUNCTION;
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void operator=(const vtkGreedyTerrainDecimation&) VTK_DELETE_FUNCTION;
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};
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#endif
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