C++：我如何使用vtk库从vti网格中读取双精度标量数据？

huangapple
go评论93阅读模式
英文:

c++: How can I read double scalar data from a vti grid using the vtk library?

问题

我正在尝试从我的vti文件中的网格中读取双精度（double）值。然而，从GetScalarPointer返回的值，在我尝试访问其中的任何元素时（例如scalarPtr[0]），会生成分段错误（segmentation fault）：

  1. #include <vtkSmartPointer.h>
  2. #include <vtkXMLImageDataReader.h>
  3. #include <vtkImageData.h>
  5. int main(){
  6.   vtkSmartPointer<vtkXMLImageDataReader> reader =
  7.       vtkSmartPointer<vtkXMLImageDataReader>::New();
  8.   reader->SetFileName("my_file.vti");
  9.   reader->Update();
  10.   vtkSmartPointer<vtkImageData> imageData = vtkSmartPointer<vtkImageData>::Take(reader->GetOutput());
  11.   double* scalarPtr = static_cast<double*>(imageData->GetScalarPointer());
  12.   std::cout << scalarPtr[0] << std::endl; // segmentation fault
  13. }

我知道类型是double，因为imageData->GetDataType()返回11，对应于VTK_DOUBLE。

我还尝试了看是否是值的字节顺序导致的问题，但是下面的代码也导致分段错误，可能是因为scalarPtr不可访问：

  1. double* scalarPtr = static_cast<double*>(imageData->GetScalarPointer());
  2. const vtkIdType numScalars = imageData->GetNumberOfPoints();
  3. const int scalarSize = sizeof(double);
  4. vtkByteSwap::SwapVoidRange(scalarPtr, numScalars, scalarSize);

这是我的vtkImageData类的内容：

  1. vtkImageData (0x556e1ad5afd0)
  2.   Debug: Off
  3.   Modified Time: 307
  4.   Reference Count: 1
  5.   Registered Events: (none)
  6.   Information: 0x556e1ad5b470
  7.   Data Released: False
  8.   Global Release Data: Off
  9.   UpdateTime: 0
  10.   Field Data:
  11.     Debug: Off
  12.     Modified Time: 307
  13.     Reference Count: 1
  14.     Registered Events: (none)
  15.     Number Of Arrays: 1
  16.     Array 0 name = comments
  17.     Number Of Components: 1
  18.     Number Of Tuples: 1
  19.   Number Of Points: 2431
  20.   Number Of Cells: 1920
  21.   Cell Data:
  22.     Debug: Off
  23.     Modified Time: 302
  24.     Reference Count: 1
  25.     Registered Events:
  26.       Registered Observers:
  27.         vtkObserver (0x556e1ad5cb00)
  28.           Event: 33
  29.           EventName: ModifiedEvent
  30.           Command: 0x556e1ad5c6a0
  31.           Priority: 0
  32.           Tag: 1
  33.     Number Of Arrays: 1
  34.     Array 0 name = material
  35.     Number Of Components: 1
  36.     Number Of Tuples: 1920
  37.     Copy Tuple Flags: ( 1 1 1 1 1 0 1 1 1 1 1 )
  38.     Interpolate Flags: ( 1 1 1 1 1 0 0 1 1 1 1 )
  39.     Pass Through Flags: ( 1 1 1 1 1 1 1 1 1 1 1 )
  40.     Scalars: (none)
  41.     Vectors: (none)
  42.     Normals: (none)
  43.     TCoords: (none)
  44.     Tensors: (none)
  45.     GlobalIds: (none)
  46.     PedigreeIds: (none)
  47.     EdgeFlag: (none)
  48.     Tangents: (none)
  49.     RationalWeights: (none)
  50.     HigherOrderDegrees: (none)
  51.   Point Data:
  52.     Debug: Off
  53.     Modified Time: 304
  54.     Reference Count: 1
  55.     Registered Events:
  56.       Registered Observers:
  57.         vtkObserver (0x556e1ad5c8e0)
  58.           Event: 33
  59.           EventName: ModifiedEvent
  60.           Command: 0x556e1ad5c6a0
  61.           Priority: 0
  62.           Tag: 1
  63.     Number Of Arrays: 0
  64.     Number Of Components: 0
  65.     Number Of Tuples: 0
  66.     Copy Tuple Flags: ( 1 1 1 1 1 0 1 1 1 1 1 )
  67.     Interpolate Flags: ( 1 1 1 1 1 0 0 1 1 1 1 )
  68.     Pass Through Flags: ( 1 1 1 1 1 1 1 1 1 1 1 )
  69.     Scalars: (none)
  70.     Vectors: (none)
  71.     Normals: (none)
  72.     TCoords: (none)
  73.     Tensors: (none)
  74.     GlobalIds: (none)
  75.     PedigreeIds: (none)
  76.     EdgeFlag: (none)
  77.     Tangents: (none)
  78.     RationalWeights: (none)
  79.     HigherOrderDegrees: (none)
  80.   Bounds:
  81.     Xmin,Xmax: (0, 5e-06)
  82.     Ymin,Ymax: (0, 8e-06)
  83.     Zmin,Zmax: (0, 6e-06)
  84.   Compute Time: 308
  85.   Spacing: (5e-07, 5e-07, 5e-07)
  86.   Origin: (0, 0, 0)
  87.   Direction: (1, 0, 0, 0, 1, 0, 0, 0, 1)
  88.   Dimensions: (11, 17, 13)
  89.   Increments: (0, 0, 0)
  90.   Extent: (0, 10, 0, 16, 0, 12)

在访问网格值方面，我可能存在什么问题？

英文:

I am trying to read the double values from a grid in my vti file. However, the return value I get from GetScalarPointer generates a segmentation fault when I try to access any element inside of it, e.g. with scalarPtr[0]:

  1. #include &lt;vtkSmartPointer.h&gt;
  2. #include &lt;vtkXMLImageDataReader.h&gt;
  3. #include &lt;vtkImageData.h&gt;
  4. int main(){
  5. vtkSmartPointer&lt;vtkXMLImageDataReader&gt; reader =
  6. vtkSmartPointer&lt;vtkXMLImageDataReader&gt;::New();
  7. reader-&gt;SetFileName(&quot;my_file.vti&quot;);
  8. reader-&gt;Update();
  9. vtkSmartPointer&lt;vtkImageData&gt; imageData = vtkSmartPointer&lt;vtkImageData&gt;::Take(reader-&gt;GetOutput());
  10. double* scalarPtr = static_cast&lt;double*&gt;(imageData-&gt;GetScalarPointer());
  11. std::cout &lt;&lt; scalarPtr[0] &lt;&lt; std::endl; // segmentation fault
  12. }

I know the type is double because imageData-&gt;GetDataType() returns 11, which corresponds to VTK_DOUBLE.

I also tried to see if it was due to the endianness of the values, but

  1. double* scalarPtr = static_cast&lt;double*&gt;(imageData-&gt;GetScalarPointer());
  2. const vtkIdType numScalars = imageData-&gt;GetNumberOfPoints();
  3. const int scalarSize = sizeof(double);
  4. vtkByteSwap::SwapVoidRange(scalarPtr, numScalars, scalarSize);

also results in a segmentation fault, probably because scalarPtr is not accessible.

These are the contents of my vtkImageData class:

  1. vtkImageData (0x556e1ad5afd0)
  2. Debug: Off
  3. Modified Time: 307
  4. Reference Count: 1
  5. Registered Events: (none)
  6. Information: 0x556e1ad5b470
  7. Data Released: False
  8. Global Release Data: Off
  9. UpdateTime: 0
  10. Field Data:
  11. Debug: Off
  12. Modified Time: 307
  13. Reference Count: 1
  14. Registered Events: (none)
  15. Number Of Arrays: 1
  16. Array 0 name = comments
  17. Number Of Components: 1
  18. Number Of Tuples: 1
  19. Number Of Points: 2431
  20. Number Of Cells: 1920
  21. Cell Data:
  22. Debug: Off
  23. Modified Time: 302
  24. Reference Count: 1
  25. Registered Events:
  26. Registered Observers:
  27. vtkObserver (0x556e1ad5cb00)
  28. Event: 33
  29. EventName: ModifiedEvent
  30. Command: 0x556e1ad5c6a0
  31. Priority: 0
  32. Tag: 1
  33. Number Of Arrays: 1
  34. Array 0 name = material
  35. Number Of Components: 1
  36. Number Of Tuples: 1920
  37. Copy Tuple Flags: ( 1 1 1 1 1 0 1 1 1 1 1 )
  38. Interpolate Flags: ( 1 1 1 1 1 0 0 1 1 1 1 )
  39. Pass Through Flags: ( 1 1 1 1 1 1 1 1 1 1 1 )
  40. Scalars: (none)
  41. Vectors: (none)
  42. Normals: (none)
  43. TCoords: (none)
  44. Tensors: (none)
  45. GlobalIds: (none)
  46. PedigreeIds: (none)
  47. EdgeFlag: (none)
  48. Tangents: (none)
  49. RationalWeights: (none)
  50. HigherOrderDegrees: (none)
  51. Point Data:
  52. Debug: Off
  53. Modified Time: 304
  54. Reference Count: 1
  55. Registered Events:
  56. Registered Observers:
  57. vtkObserver (0x556e1ad5c8e0)
  58. Event: 33
  59. EventName: ModifiedEvent
  60. Command: 0x556e1ad5c6a0
  61. Priority: 0
  62. Tag: 1
  63. Number Of Arrays: 0
  64. Number Of Components: 0
  65. Number Of Tuples: 0
  66. Copy Tuple Flags: ( 1 1 1 1 1 0 1 1 1 1 1 )
  67. Interpolate Flags: ( 1 1 1 1 1 0 0 1 1 1 1 )
  68. Pass Through Flags: ( 1 1 1 1 1 1 1 1 1 1 1 )
  69. Scalars: (none)
  70. Vectors: (none)
  71. Normals: (none)
  72. TCoords: (none)
  73. Tensors: (none)
  74. GlobalIds: (none)
  75. PedigreeIds: (none)
  76. EdgeFlag: (none)
  77. Tangents: (none)
  78. RationalWeights: (none)
  79. HigherOrderDegrees: (none)
  80. Bounds:
  81. Xmin,Xmax: (0, 5e-06)
  82. Ymin,Ymax: (0, 8e-06)
  83. Zmin,Zmax: (0, 6e-06)
  84. Compute Time: 308
  85. Spacing: (5e-07, 5e-07, 5e-07)
  86. Origin: (0, 0, 0)
  87. Direction: (1, 0, 0, 0, 1, 0, 0, 0, 1)
  88. Dimensions: (11, 17, 13)
  89. Increments: (0, 0, 0)
  90. Extent: (0, 10, 0, 16, 0, 12)

What am I doing wrong in terms of how I am accessing the grid values?

答案1

得分: 0

以下是代码的翻译部分：

解决方案是选择正确的XML嵌套级别，即ImageData -> CellData -> DataArray：

  1. #include <vtkSmartPointer.h>
  2. #include <vtkXMLImageDataReader.h>
  3. #include <vtkImageData.h>
  4. #include <vtkCellData.h>
  5. #include <vtkIntArray.h>
  7. int main() {
  8.   vtkSmartPointer<vtkXMLImageDataReader> reader =
  9.       vtkSmartPointer<vtkXMLImageDataReader>::New();
  10.   reader->SetFileName("my_file.vti");
  11.   reader->Update();
  13.   vtkSmartPointer<vtkImageData> imageData = reader->GetOutput();
  14.   vtkSmartPointer<vtkCellData> cellData = imageData->GetCellData();
  15.   vtkSmartPointer<vtkDataArray> dataArray = cellData->GetArray("material");
  17.   int dims[3];
  18.   imageData->GetDimensions(dims);
  19.   for (int i = 0; i < 3; ++i) dims[i] = dims[i] - 1;
  21.   for (int k = 0; k <= dims[2]; k++) {
  22.       for (int j = 0; j <= dims[1]; j++) {
  23.           for (int i = 0; i <= dims[0]; i++) {
  24.               double value = dataArray->GetComponent(
  25.                   i + j * dims[0] + k * dims[0] * dims[1], 0);
  26.               std::cout << "Value at (" << i << ", " << j << ", " << k << "): " 
  27.                         << value << std::endl;
  28.           }
  29.       }
  30.   }
  31. }

希望这对你有所帮助。如果你有任何其他问题，可以随时提出。

英文:

The solution was to select the correct XML nesting level, which was ImageData -> CellData -> DataArray:

  1. #include &lt;vtkSmartPointer.h&gt;
  2. #include &lt;vtkXMLImageDataReader.h&gt;
  3. #include &lt;vtkImageData.h&gt;
  4. #include &lt;vtkCellData.h&gt;
  5. #include &lt;vtkIntArray.h&gt;
  6. int main(){
  7. vtkSmartPointer&lt;vtkXMLImageDataReader&gt; reader =
  8. vtkSmartPointer&lt;vtkXMLImageDataReader&gt;::New();
  9. reader-&gt;SetFileName(&quot;my_file.vti&quot;);
  10. reader-&gt;Update();
  11. vtkSmartPointer&lt;vtkImageData&gt; imageData = reader-&gt;GetOutput();
  12. vtkSmartPointer&lt;vtkCellData&gt; cellData = imageData-&gt;GetCellData();
  13. vtkSmartPointer&lt;vtkDataArray&gt; dataArray = cellData-&gt;GetArray(&quot;material&quot;);
  14. int dims[3];
  15. imageData-&gt;GetDimensions(dims);
  16. for (int i = 0; i &lt; 3; ++i) dims[i] = dims[i]-1;
  17. for (int k = 0; k &lt;= dims[2]; k++) {
  18. for (int j = 0; j &lt;= dims[1]; j++) {
  19. for (int i = 0; i &lt;= dims[0]; i++) {
  20. double value = dataArray-&gt;GetComponent(
  21. i + j * dims[0] + k * dims[0] * dims[1], 0);
  22. std::cout &lt;&lt; &quot;Value at (&quot; &lt;&lt; i &lt;&lt; &quot;, &quot; &lt;&lt; j &lt;&lt; &quot;, &quot; &lt;&lt; k &lt;&lt; &quot;): &quot; 
  23. &lt;&lt; value &lt;&lt; std::endl;
  24. }
  25. }
  26. }
  27. }

huangapple
  • 本文由 发表于 2023年3月3日 23:08:26
  • 转载请务必保留本文链接：https://go.coder-hub.com/75628757.html
  • c++
  • vtk
匿名

发表评论

匿名网友

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

确定