1 /*=========================================================================
2 
3   Program:   Visualization Toolkit
4   Module:    vtkFlyingEdges2D.h
5 
6   Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
7   All rights reserved.
8   See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
9 
10      This software is distributed WITHOUT ANY WARRANTY; without even
11      the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
12      PURPOSE.  See the above copyright notice for more information.
13 
14 =========================================================================*/
15 /**
16  * @class   vtkFlyingEdges2D
17  * @brief   generate isoline(s) from a structured points (image) dataset
18  *
19  * vtkFlyingEdges2D is a reference implementation of the 2D version of the
20  * flying edges algorithm. It is designed to be highly scalable (i.e.,
21  * parallelizable) for large data. It implements certain performance
22  * optimizations including computational trimming to rapidly eliminate
23  * processing of data regions, packed bit representation of case table
24  * values, single edge intersection, elimination of point merging, and
25  * elimination of any reallocs (due to dynamic data insertion). Note that
26  * computational trimming is a method to reduce total computational cost in
27  * which partial computational results can be used to eliminate future
28  * computations.
29  *
30  * This is a four-pass algorithm. The first pass processes all x-edges and
31  * builds x-edge case values (which, when the two x-edges defining a pixel
32  * are combined, are equivalent to vertex-based case table except edge-based
33  * approaches are separable to parallel computing). Next x-pixel rows are
34  * processed to gather information from y-edges (basically to count the
35  * number of edge intersections and lines generated). In the third pass a
36  * prefix sum is used to count and allocate memory for the output
37  * primitives. Finally in the fourth pass output primitives are generated into
38  * pre-allocated arrays. This implementation uses pixel cell axes (a x-y dyad
39  * located at the pixel origin) to ensure that each edge is intersected at
40  * most one time.
41  *
42  * See the paper "Flying Edges: A High-Performance Scalable Isocontouring
43  * Algorithm" by Schroeder, Maynard, Geveci. Proc. of LDAV 2015. Chicago, IL.
44  *
45  * @warning
46  * This filter is specialized to 2D images. This implementation can produce
47  * degenerate line segments (i.e., zero-length line segments).
48  *
49  * @warning
50  * If you are interested in extracting segmented regions from a label mask,
51  * consider using vtkDiscreteFlyingEdges2D.
52  *
53  * @warning
54  * This class has been threaded with vtkSMPTools. Using TBB or other
55  * non-sequential type (set in the CMake variable
56  * VTK_SMP_IMPLEMENTATION_TYPE) may improve performance significantly.
57  *
58  * @sa
59  * vtkFlyingEdges3D vtkContourFilter vtkSynchronizedTemplates2D
60  * vtkMarchingSquares vtkDiscreteFlyingEdges2D
61 */
62 
63 #ifndef vtkFlyingEdges2D_h
64 #define vtkFlyingEdges2D_h
65 
66 #include "vtkFiltersCoreModule.h" // For export macro
67 #include "vtkPolyDataAlgorithm.h"
68 #include "vtkContourValues.h" // Needed for direct access to ContourValues
69 
70 class vtkImageData;
71 
72 class VTKFILTERSCORE_EXPORT vtkFlyingEdges2D : public vtkPolyDataAlgorithm
73 {
74 public:
75   static vtkFlyingEdges2D *New();
76   vtkTypeMacro(vtkFlyingEdges2D,vtkPolyDataAlgorithm);
77   void PrintSelf(ostream& os, vtkIndent indent) override;
78 
79   /**
80    * Because we delegate to vtkContourValues.
81    */
82   vtkMTimeType GetMTime() override;
83 
84   /**
85    * Set a particular contour value at contour number i. The index i ranges
86    * between 0<=i<NumberOfContours.
87    */
SetValue(int i,double value)88   void SetValue(int i, double value)
89     {this->ContourValues->SetValue(i,value);}
90 
91   /**
92    * Get the ith contour value.
93    */
GetValue(int i)94   double GetValue(int i)
95     {return this->ContourValues->GetValue(i);}
96 
97   /**
98    * Get a pointer to an array of contour values. There will be
99    * GetNumberOfContours() values in the list.
100    */
GetValues()101   double *GetValues()
102     {return this->ContourValues->GetValues();}
103 
104   /**
105    * Fill a supplied list with contour values. There will be
106    * GetNumberOfContours() values in the list. Make sure you allocate
107    * enough memory to hold the list.
108    */
GetValues(double * contourValues)109   void GetValues(double *contourValues)
110     {this->ContourValues->GetValues(contourValues);}
111 
112   /**
113    * Set the number of contours to place into the list. You only really
114    * need to use this method to reduce list size. The method SetValue()
115    * will automatically increase list size as needed.
116    */
SetNumberOfContours(int number)117   void SetNumberOfContours(int number)
118     {this->ContourValues->SetNumberOfContours(number);}
119 
120   /**
121    * Get the number of contours in the list of contour values.
122    */
GetNumberOfContours()123   int GetNumberOfContours()
124     {return this->ContourValues->GetNumberOfContours();}
125 
126   /**
127    * Generate numContours equally spaced contour values between specified
128    * range. Contour values will include min/max range values.
129    */
GenerateValues(int numContours,double range[2])130   void GenerateValues(int numContours, double range[2])
131     {this->ContourValues->GenerateValues(numContours, range);}
132 
133   /**
134    * Generate numContours equally spaced contour values between specified
135    * range. Contour values will include min/max range values.
136    */
GenerateValues(int numContours,double rangeStart,double rangeEnd)137   void GenerateValues(int numContours, double rangeStart, double rangeEnd)
138     {this->ContourValues->GenerateValues(numContours, rangeStart, rangeEnd);}
139 
140   //@{
141   /**
142    * Option to set the point scalars of the output.  The scalars will be the
143    * iso value of course.  By default this flag is on.
144    */
145   vtkSetMacro(ComputeScalars,vtkTypeBool);
146   vtkGetMacro(ComputeScalars,vtkTypeBool);
147   vtkBooleanMacro(ComputeScalars,vtkTypeBool);
148   //@}
149 
150   //@{
151   /**
152    * Set/get which component of the scalar array to contour on; defaults to 0.
153    */
154   vtkSetMacro(ArrayComponent, int);
155   vtkGetMacro(ArrayComponent, int);
156   //@}
157 
158 protected:
159   vtkFlyingEdges2D();
160   ~vtkFlyingEdges2D() override;
161 
162   int RequestData(vtkInformation *, vtkInformationVector **,
163                   vtkInformationVector *) override;
164   int FillInputPortInformation(int port, vtkInformation *info) override;
165   vtkContourValues *ContourValues;
166 
167   vtkTypeBool ComputeScalars;
168   int ArrayComponent;
169 
170 private:
171   vtkFlyingEdges2D(const vtkFlyingEdges2D&) = delete;
172   void operator=(const vtkFlyingEdges2D&) = delete;
173 };
174 
175 
176 #endif
177