[VTK] Surface of Revolution

 VTK에는 내가 원하는 Surface of Revolution API가 없습니다.

vtkRotationalExtrusionFilter라는 클래스가 있지만 원하는 결과를 만들어 주지 않았습니다.

그렇게 원하는 API를 찾아봤는데 찾지 못했기 때문에 그 기능을 직접 구현하기로 했습니다.

먼저 회전시킬 곡선(Profile)을 생성합니다.

Profile을 회전 축을 기준으로 Resolution만큼 회전시키면서 곡선들을 만들어 냅니다.

1. # create a profile
2. circle = vtk.vtkRegularPolygonSource()
3. circle.SetCenter((pt1[0] - self._origin[0], pt1[1] - self._origin[1], pt1[2] - self._origin[2]))
4. circle.SetNormal((pt1[0] - center[0], pt1[1] - center[1], pt1[2] - center[2]))
5. circle.SetRadius(radius)
6. circle.SetNumberOfSides(24)
7. circle.Update()
8. circle_points = circle.GetOutput().GetPoints() # get points from profile
9. del circle
10.  
11. # Setup points and lines
12. points = vtk.vtkPoints()
13. points.Allocate((self._resolution + 1) * circle_points.GetNumberOfPoints())
14. faces = vtk.vtkCellArray()
15. faces.SetNumberOfCells(self._resolution * circle_points.GetNumberOfPoints())
16. lines = vtk.vtkCellArray()
17.  
18. num = circle_points.GetNumberOfPoints()
19. for idx in range(num):
20. points.InsertNextPoint(circle_points.GetPoint(idx))
21. if idx < num - 1:
22. line = vtk.vtkLine()
23. line.GetPointIds().SetId(0, idx)
24. line.GetPointIds().SetId(1, idx + 1)
25. lines.InsertNextCell(line)
26. else:
27. line = vtk.vtkLine()
28. line.GetPointIds().SetId(0, idx)
29. line.GetPointIds().SetId(1, 0)
30. lines.InsertNextCell(line)
31.  
32. appended_polydata = vtk.vtkAppendPolyData()
33.  
34. polydata = vtk.vtkPolyData()
35. polydata.SetPoints(circle_points)
36. polydata.SetLines(lines)
37. appended_polydata.AddInputData(polydata)
38.  
39. # 축 벡터 구하기
40. vectors = [(center[0] - pt1[0], center[1] - pt1[1], center[2] - pt1[2]),
41. (pt2[0] - pt1[0], pt2[1] - pt1[1], pt2[2] - pt1[2])]
42. normal = [0, 0, 0]
43. vtk.vtkMath.Cross(vectors[0], vectors[1], normal)
44. vtk.vtkMath.Normalize(normal)
45.  
46. # rotate about normal vector
47. transform = vtk.vtkTransform()
48. transform.Identity()
49. transform.RotateWXYZ(angle/self._resolution, normal[0], normal[1], normal[2])
50.  
51. for idx in range(self._resolution):
52. transform_filter = vtk.vtkTransformPolyDataFilter()
53. transform_filter.SetInputData(polydata)
54. transform_filter.SetTransform(transform)
55. transform_filter.Update()
56. polydata = transform_filter.GetOutput()
57.  
58. for idx_ in range(num):
59. points.InsertNextPoint(polydata.GetPoint(idx_))
60.  
61. appended_polydata.AddInputData(polydata)
62. appended_polydata.Update()

생성한 곡선들을 연결하여 곡면을 만들어 냅니다.

1. for v in range(self._resolution):
2. for u in range(circle_points.GetNumberOfPoints()):
3. faces.InsertNextCell(4, [v*circle_points.GetNumberOfPoints() + u,
4. v*circle_points.GetNumberOfPoints() + (u + 1) % circle_points.GetNumberOfPoints(),
5. (v + 1)*circle_points.GetNumberOfPoints() + (u + 1) % circle_points.GetNumberOfPoints(),
6. (v + 1)*circle_points.GetNumberOfPoints() + u])
7.  
8. output = vtk.vtkPolyData()
9. output.SetPoints(points)
10. output.SetPolys(faces)

이렇게 해서 두 파이프를 연결하는 엘보를 생성하였습니다.