How to Pick Edge?

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1

Hi！my current Polydata contains Line but not Ploy. I want to pick up the relevant information of such a red line. How should I do it?

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(ps:I presuppose that I have the polyline selected and go to render)
Now,My current operation idea wants to be processed through CellPicker; because in my understanding, Line, PolyLine, and Poly can all be called Cells, but I have not succeeded in implementing them.
The data aspect has the index number corresponding to each line and the coordinate value of the vertex that a line contains.
I will humbly accept any suggestion you give me!
Thanks for everyone’s help!

2

Add an observer to the interactor, the object in the handler will be the interactor

def MousePress(iren , ev):
  renWin = iren.GetRenderWindow()
  pos = irenj.GetEventPosition()
  renderer = obj.FindPokedRenderer(pos[0], pos[1])

  x, y = iren.GetEventPosition()
  picker = vtk.vtkWorldPointPicker()
  picker.Pick(x, y, 0, renderer)
  worldPoint = picker.GetPickPosition()
  print('world point from vtkPropPicker: ', worldPoint)
  # Now you could add a small sphere to show the position
  sphere = vtk.vtkSphereSource()
  sphere.SetCenter(worldPoint[0], worldPoint[1], worldPoint[2])
  sphere.SetRadius(sphereRadius)
  sphere.Update()
  sphereMapper = vtk.vtkPolyDataMapper()
  sphereMapper.SetInputData(sphere.GetOutput())
  sphereActor = vtk.vtkActor()
  sphereActor.SetMapper(sphereMapper)
  sphereActor.GetProperty().SetColor(255, 0, 0)
  renderer.AddActor(sphereActor)
  renderer.Render()

You can store the last actor to remove the previous to avoid adding to many spheres. Was it something like this you had in mind?
3

Thanks for your replay!
But maybe I don’t think so;
What I mean is: I want to pick a line on the model, like this and the red line, but I don’t know how I can do it.
In other words, when I click on the model, I want to pick the line,what should I do？

4

You mean: when I click on the model, return me a world coordinate value, and render a sphere for labeling,this is my understanding.
I have considered using the coordinate value to judge the line segment before, but there will be some problems;
I’m wondering if there’s a better way.

5

What do you mean by judge the line segment? I wasn’t really sure what you were trying to achieve and thought that you might wanted the world position for a point in the scene. What do you mean by data aspect has an index number. Where is the red line?

If you want information about a cell that you pick, you can use a cell picker as shown here.

https://kitware.github.io/vtk-examples/site/Cxx/Picking/CellPicking/

Change the example a bit:

plane_source.SetResolution(10,10)
selection_node.SetContentType(vtkSelectionNode.VERTEX)

I believe the author meant to have used this content type when creating the example. Press ‘w’ and you will see a wireframe with all edges of the picked triangle highlighted.

6

Did you check that hardware selector example ?

2 Likes
7

I guess this using the hardware accelerated picker. Picking using color codes. I used that for a standalone C++ application.

8

In general, it difficult to pick lines. They are thin. In the example I am referring to, you pick the cells and color both the facet and lines surrounding it. If the hardware accelerated example shown below is available I would look into that.

9

Thanks for your replay and suggestion!
I didn’t expect such a suitable example!
I am directly searching for relevant knowledge about Picker, I will continue to advance according to your suggestion!

10

Yes, I thought about using GPU Picker for picking like Three.js.
Due to lack of personal ability, there is no reasonable promotion.
I will continue to promote research, and welcome to continue to communicate if there is relevant progress.