• VTK中Clip/Trim总结

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    前言

    本博文主要介绍VTK中几个常见的Clip/Trim接口，同时介绍下3-matic软件中对应的功能；希望能帮到各位小伙伴，有什么问题欢迎交流学习。

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    目录

    前言

    1. VTK中裁剪接口

    2. vtkClipPolyData 

    3. vtkClipClosedSurface

    4. vtkClipClosedSurface示例

    结论：

    1. VTK中裁剪接口

            vtk中针对剪裁有多个接口，各自有优点和缺点，现详细列出，小伙伴可以有针对性的进行选择接口。裁剪的接口有vtkClipClosedSurface 、vtkClipConvexPolyData 、 vtkClipDataSet 、 vtkClipPolyData 、vtkClipVolume。目前主要介绍vtkClipClosedSurface 、 vtkClipPolyData两个接口。

    效果图

    vtkClipPolyData效果图 

     

    vtkClipClosedSurface效果图 

    两者差异：vtkClipPolyData切割带有锯齿形状且不是封闭的模型；vtkClipClosedSurface通过插值确保切割面为光滑且封闭的。

    2. vtkClipPolyData 

    用途：通过用户定义的隐函数或输入的标量数据，裁剪polygonal data。

            采用隐函数裁剪的方法：定义裁剪隐函数；SetClipFunction; GenerateClipScalarsOn;

    核心算法：

    1.   if (this->ClipFunction)
    2.   {
    3.     vtkFloatArray* tmpScalars = vtkFloatArray::New();
    4.     tmpScalars->SetNumberOfTuples(numPts);
    5.     inPD = vtkPointData::New();
    6.     inPD->ShallowCopy(input->GetPointData()); // copies original
    7.     if (this->GenerateClipScalars)
    8.     {
    9.       inPD->SetScalars(tmpScalars);
    10.     }
    11.     for (i = 0; i < numPts; i++)
    12.     {
    13. //遍历输入数据的每个点，计算是否满足ClipFunction的条件；若ClipFunction为vtkPolyPlane,则判断点是否在PolyLine内，若在内，则s为正数；反之为负数。
    14.       s = this->ClipFunction->FunctionValue(inPts->GetPoint(i));
    15.       tmpScalars->SetComponent(i, 0, s);
    16.     }
    17.     clipScalars = tmpScalars;
    18.   }
    19.  
    20. //用上述判定点的结果对cell进行分割
    21. cell->Clip(this->Value, cellScalars, this->Locator, connList, inPD, outPD, inCD, cellId, outCD,
    22.       this->InsideOut);

    3. vtkClipClosedSurface

    用途：通过一组切割平面实现对闭合曲面的切割。将输入数据切割未由多边形面组成的闭合曲面。

    约束：输入的曲面不应该有开放的边缘，也不能有任何被两个以上的面共享的边缘。            vtkFeatureEdges过滤器可以用来验证一个数据集是否满足这些条件。此外，输入的面不应该是自相交的，即曲面的各个面应该只与它们的边缘相接触。

    选项：

    a. 如果 "生成轮廓"（GenerateOutline）是打开的，这个过滤器将在剪裁平面与数据相交处生成一个轮廓，如下图所示。

    b. PassPointData；若打开表示将点数据传递给输出，若新点产生时，点数据将会进行插值。此变量默认关闭。

     c. ScalarMode选项将在输出中添加单元格标量，这样生成的面就可以用与原始面不同的颜色显示。可以用与原始表面不同的颜色来显示。

    注意：

    （1）一组切割平面应该是一组凸平面，否则生成的结果可能为空。

    （2）生成的结果为多个平面围成的部分。

    （3）若ScalarMode设置为On时，则是通过标量来映射Mapper的颜色；此时通过

            actor->GetProperty()->SetColor(color);设置颜色时不生效；解决方案：关闭Mapper的

            ScalarVisibility，颜色设置才能生效。

    核心算法：

    1. // Go through the clipping planes and clip the input with each plane
    2.   vtkCollectionSimpleIterator iter;
    3.   int numPlanes = 0;
    4.   if (planes)
    5.   {
    6.     planes->InitTraversal(iter);
    7.     numPlanes = planes->GetNumberOfItems();
    8.   }
    9.  
    10.   vtkPlane* plane = nullptr;
    11.   for (int planeId = 0; planes && (plane = planes->GetNextPlane(iter)); planeId++)
    12.   {
    13.     this->UpdateProgress((planeId + 1.0) / (numPlanes + 1.0));
    14.     if (this->GetAbortExecute())
    15.     {
    16.       break;
    17.     }
    18.  
    19.     // Is this the last cut plane?  If so, generate triangles.
    20.     int triangulate = 5;
    21.     if (planeId == numPlanes - 1)
    22.     {
    23.       triangulate = polyMax;
    24.     }
    25.  
    26.     // Is this the active plane?
    27.     int active = (planeId == this->ActivePlaneId);
    28.  
    29.     // Convert the plane into an easy-to-evaluate function
    30.     double pc[4];
    31.     plane->GetNormal(pc);
    32.     pc[3] = -vtkMath::Dot(pc, plane->GetOrigin());
    33.  
    34.     // Create the clip scalars by evaluating the plane at each point
    35.     vtkIdType numPoints = points->GetNumberOfPoints();
    36.     pointScalars->SetNumberOfValues(numPoints);
    37.     for (vtkIdType pointId = 0; pointId < numPoints; pointId++)
    38.     {
    39.       double p[3];
    40.       points->GetPoint(pointId, p);
    41.  
    42. //*重要*计算每个点到切平面的距离，若>0表示该点在切平面的法向方向上，若<0表示该点在切平面法向的反方向上
    43.       double val = p[0] * pc[0] + p[1] * pc[1] + p[2] * pc[2] + pc[3];
    44.       pointScalars->SetValue(pointId, val);
    45.     }
    46.  
    47.     // Prepare the output scalars
    48.     outLineData->CopyAllocate(inLineData, 0, 0);
    49.     outPolyData->CopyAllocate(inPolyData, 0, 0);
    50.  
    51.     // Reset the locator
    52.     edgeLocator->Initialize();
    53.  
    54.     // Clip the lines
    55. //*重要*若直线的两点均在切平面法向的相反方向，则过滤掉该直线；若直线的两点均在切平面法向上，则保留该直线；若直线与切平面相交，则对该直线进行插值，保留切平面法向方向上的直线部分。
    56.     this->ClipLines(
    57.       points, pointScalars, pointData, edgeLocator, lines, newLines, inLineData, outLineData);
    58.  
    59.     // Clip the polys
    60.     if (polys)
    61.     {
    62.       // Get the number of lines remaining after the clipping
    63.       vtkIdType numClipLines = newLines->GetNumberOfCells();
    64.  
    65.       // Cut the polys to generate more lines
    66. //*重要*获取组成该多边形的点，若某边与切平面相交则进行插值；
    67.       this->ClipAndContourPolys(points, pointScalars, pointData, edgeLocator, triangulate, polys,
    68.         newPolys, newLines, inPolyData, outPolyData, outLineData);
    69.  
    70.       // Add scalars for the newly-created contour lines
    71.       vtkUnsignedCharArray* scalars =
    72.         vtkArrayDownCast(outLineData->GetScalars());
    73.  
    74.       if (scalars)
    75.       {
    76.         // Set the color to the active color if plane is active
    77.         unsigned char* color = colors[1 + active];
    78.         unsigned char* activeColor = colors[2];
    79.  
    80.         vtkIdType numLines = newLines->GetNumberOfCells();
    81.         for (vtkIdType lineId = numClipLines; lineId < numLines; lineId++)
    82.         {
    83.           unsigned char oldColor[3];
    84.           scalars->GetTypedTuple(lineId, oldColor);
    85.           if (numberOfScalarComponents != 3 || oldColor[0] != activeColor[0] ||
    86.             oldColor[1] != activeColor[1] || oldColor[2] != activeColor[2])
    87.           {
    88.             scalars->SetTypedTuple(lineId, color);
    89.           }
    90.         }
    91.       }
    92.  
    93.       // Generate new polys from the cut lines
    94.       vtkIdType cellId = newPolys->GetNumberOfCells();
    95.       vtkIdType numClipAndContourLines = newLines->GetNumberOfCells();
    96.  
    97.       // Create a polydata for the lines
    98.       tmpContourData->SetPoints(points);
    99.       tmpContourData->SetLines(newLines);
    100.       tmpContourData->BuildCells();
    101.  
    102.       this->TriangulateContours(
    103.         tmpContourData, numClipLines, numClipAndContourLines - numClipLines, newPolys, pc);
    104.  
    105.       // Add scalars for the newly-created polys
    106.       scalars = vtkArrayDownCast(outPolyData->GetScalars());
    107.  
    108.       if (scalars)
    109.       {
    110.         unsigned char* color = colors[1 + active];
    111.  
    112.         vtkIdType numCells = newPolys->GetNumberOfCells();
    113.         if (numCells > cellId)
    114.         {
    115.           // The insert allocates space up to numCells-1
    116.           scalars->InsertTypedTuple(numCells - 1, color);
    117.           for (; cellId < numCells; cellId++)
    118.           {
    119.             scalars->SetTypedTuple(cellId, color);
    120.           }
    121.         }
    122.       }
    123.  
    124.       // Add scalars to any diagnostic lines that added by
    125.       // TriangulateContours().  In usual operation, no lines are added.
    126.       scalars = vtkArrayDownCast(outLineData->GetScalars());
    127.  
    128.       if (scalars)
    129.       {
    130.         unsigned char color[3] = { 0, 255, 255 };
    131.  
    132.         vtkIdType numCells = newLines->GetNumberOfCells();
    133.         if (numCells > numClipAndContourLines)
    134.         {
    135.           // The insert allocates space up to numCells-1
    136.           scalars->InsertTypedTuple(numCells - 1, color);
    137.           for (vtkIdType lineCellId = numClipAndContourLines; lineCellId < numCells; lineCellId++)
    138.           {
    139.             scalars->SetTypedTuple(lineCellId, color);
    140.           }
    141.         }
    142.       }
    143.     }
    144.  
    145.     // Swap the lines, points, etcetera: old output becomes new input
    146.     vtkCellArray* tmp1 = lines;
    147.     lines = newLines;
    148.     newLines = tmp1;
    149.     newLines->Initialize();
    150.  
    151.     if (polys)
    152.     {
    153.       vtkCellArray* tmp2 = polys;
    154.       polys = newPolys;
    155.       newPolys = tmp2;
    156.       newPolys->Initialize();
    157.     }
    158.  
    159.     vtkCellData* tmp4 = inLineData;
    160.     inLineData = outLineData;
    161.     outLineData = tmp4;
    162.     outLineData->Initialize();
    163.  
    164.     vtkCellData* tmp5 = inPolyData;
    165.     inPolyData = outPolyData;
    166.     outPolyData = tmp5;
    167.     outPolyData->Initialize();
    168.   }

    4. vtkClipClosedSurface示例

            》vtkAreaPicker：获取裁剪平面

            》vtkClipClosedSurface：完成裁剪

    代码：

    1. #include 
    2. #include 
    3. #include 
    4. #include 
    5. #include 
    6. #include 
    7. #include 
    8. #include 
    9. #include 
    10. #include 
    11. #include 
    12. #include 
    13. #include 
    14. #include 
    15. #include 
    16. #include 
    17. #include 
    18. #include 
    19. #include 
    20. #include 
    21. #include 
    22. #include 
    23. #include 
    24. #include 
    25. #include 
    26. #include 
    27. #include 
    28. #include "vtkClipClosedSurface.h"
    29. #include "vtkPlaneCollection.h"
    30. #include "vtkAxesActor.h"
    31. #define VTKISRBP_ORIENT 0
    32. #define VTKISRBP_SELECT 1
    33.  
    34.  
    35. namespace {
    36. 	// Define interaction style
    37. 	class HighlightInteractorStyle : public vtkInteractorStyleRubberBandPick
    38. 	{
    39. 	public:
    40. 		static HighlightInteractorStyle* New();
    41. 		vtkTypeMacro(HighlightInteractorStyle, vtkInteractorStyleRubberBandPick);
    42.  
    43. 		HighlightInteractorStyle() : vtkInteractorStyleRubberBandPick()
    44. 		{
    45. 			this->SelectedMapper = vtkSmartPointer::New();
    46. 			this->SelectedActor = vtkSmartPointer::New();
    47. 			this->SelectedActor->SetMapper(SelectedMapper);
    48. 		}
    49.  
    50. 		virtual void OnLeftButtonUp() override
    51. 		{
    52. 			// Forward events
    53. 			vtkInteractorStyleRubberBandPick::OnLeftButtonUp();
    54.  
    55. 			if (this->CurrentMode == VTKISRBP_SELECT)
    56. 			{
    57. 				vtkNew colors;
    58.  
    59. 				vtkPlanes* frustum = static_cast(this->GetInteractor()->GetPicker())->GetFrustum();
    60.  
    61. 				vtkNew planeCollection;
    62. 				int pCount = frustum->GetNumberOfPlanes() - 2;
    63. 				for (int i = 0; i < pCount; i++)
    64. 				{
    65. 					double normal[3];
    66. 					frustum->GetPlane(i)->GetNormal(normal);
    67. 					double origin[3];
    68. 					frustum->GetPlane(i)->GetOrigin(origin);
    69.  
    70. 					vtkNew plane;
    71. 					plane->SetOrigin(origin[0], origin[1], origin[2]);
    72. 					plane->SetNormal(-normal[0], -normal[1], -normal[2]);
    73. 					planeCollection->AddItem(plane);
    74. 				}
    75. 				
    76. 				vtkNew clipper;
    77. 				clipper->SetInputData(this->PolyData);
    78. 				clipper->SetClippingPlanes(planeCollection);
    79. 				clipper->Update();
    80.  
    81. 				if (m_SrcActor != nullptr)
    82. 					m_SrcActor->VisibilityOff();
    83.  
    84. 				this->SelectedMapper->SetInputData(clipper->GetOutput());
    85.  
    86. 				this->SelectedActor->GetProperty()->SetColor(1.0000, 0.3882, 0.2784);
    87. 				this->GetInteractor()->GetRenderWindow()->GetRenderers()->GetFirstRenderer()->AddActor(SelectedActor);
    88. 				this->GetInteractor()->GetRenderWindow()->Render();
    89. 				this->HighlightProp(NULL);
    90. 			}
    91. 		}
    92.  
    93. 		void SetPolyData(vtkSmartPointer polyData)
    94. 		{
    95. 			this->PolyData = polyData;
    96. 		}
    97. 		vtkActor* m_SrcActor = nullptr;
    98. 	private:
    99. 		vtkSmartPointer PolyData;
    100. 		vtkSmartPointer SelectedActor;
    101. 		vtkSmartPointer SelectedMapper;
    102. 	};
    103. 	vtkStandardNewMacro(HighlightInteractorStyle);
    104.  
    105. } // namespace
    106.  
    107. int main(int argc, char* argv[])
    108. {
    109.  
    110. 	vtkNew source;
    111. 	source->SetPhiResolution(49);
    112. 	source->SetThetaResolution(200);
    113. 	source->Update();
    114. 	auto polyData = source->GetOutput();
    115.  
    116.  
    117. 	// Create a mapper and actor
    118. 	vtkNew mapper;
    119. 	mapper->SetInputData(polyData);
    120. 	mapper->ScalarVisibilityOff();
    121.  
    122. 	vtkNew actor;
    123. 	actor->SetMapper(mapper);
    124. 	actor->GetProperty()->SetPointSize(5);
    125.  
    126. 	vtkNew axes;
    127. 	// Visualize
    128. 	vtkNew renderer;
    129. 	renderer->UseHiddenLineRemovalOn();
    130.  
    131. 	vtkNew renderWindow;
    132. 	renderWindow->AddRenderer(renderer);
    133. 	renderWindow->SetSize(640, 480);
    134. 	renderWindow->SetWindowName("HighlightSelection");
    135.  
    136. 	vtkNew areaPicker;
    137. 	vtkNew renderWindowInteractor;
    138. 	renderWindowInteractor->SetPicker(areaPicker);
    139. 	renderWindowInteractor->SetRenderWindow(renderWindow);
    140.  
    141. 	renderer->AddActor(actor);
    142. 	renderer->AddActor(axes);
    143.  
    144. 	renderWindow->Render();
    145.  
    146. 	vtkNew style;
    147. 	style->m_SrcActor = actor;
    148. 	style->SetPolyData(polyData);
    149. 	style->SetCurrentRenderer(renderer);
    150. 	renderWindowInteractor->SetInteractorStyle(style);
    151.  
    152. 	renderWindowInteractor->Start();
    153.  
    154. 	return EXIT_SUCCESS;
    155. }
    156.

    结论：

            本文主要介绍了vtkClipPolyData 和 vtkClipClosedSurface两个接口的使用方法、两者的处理结果和缺点。

    感谢各位小伙伴的点赞+关注，小易会继续努力分享，一起进步！

    你的赞赏是我的最最最最大的动力(＾Ｕ＾)ノ~ＹＯ

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  • 原文地址：https://blog.csdn.net/qq_40041064/article/details/127789425