Does vtkCellPicker conside point size?

Support
1

Please have a look for the following code:


import vtkmodules.all as vtk

polyData = vtk.vtkPolyData()
polyData.SetPoints(vtk.vtkPoints())
polyData.SetVerts(vtk.vtkCellArray())

polyData.GetPoints().InsertNextPoint(1, 1, 1)
polyData.GetVerts().InsertNextCell(1)
polyData.GetVerts().InsertCellPoint(0)

polyData.GetPoints().Modified()
polyData.GetVerts().Modified()
polyData.Modified()

mapper = vtk.vtkPolyDataMapper()
mapper.SetInputData(polyData)
actor = vtk.vtkActor()
actor.SetMapper(mapper)
actor.GetProperty().SetColor(255, 255, 0)
actor.GetProperty().SetPointSize(10)  ################### point size

def mousemove(iren, event):
    pos = iren.GetEventPosition()
    picker = vtk.vtkCellPicker()
    picker.SetTolerance(0.01)
    picker.Pick(pos[0], pos[1], 0, render)
    actor = picker.GetProp3D()
    if actor == None:
        print('no actor')
    else:
        print('pick actor')

render = vtk.vtkRenderer()
render.AddActor(actor)
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(render)
renWin.Render()
iren = vtk.vtkRenderWindowInteractor()
iren.AddObserver('MouseMoveEvent', mousemove)
iren.SetRenderWindow(renWin)
iren.Initialize()
iren.Start()

In the above code, I can pick the point as I expect. However, when I change the point size to 50:

actor.GetProperty().SetPointSize(50)

I find that I can pick the actor only when the cursor move inside the red rectangle in the following picture.

image

I think it is because the vtkCellPicker do not conside the point size. Am I correct?

I have read the source code of vtkCellPicker and vtkPicker, and I actually do not find where the vtkCellPicker conside the point size or line width.

Or is there something wrong with my test code?

2

VtkCellPicker is a geometric operation that does not consider the graphics representation. So the point size graphics property is ignored. If you want that taken into account, you might try vtkPropPicker.

3

@will.schroeder Thank you for your reply. In vtkPropPicker, the vtkHardwareSelector is used. The vtkHardwareSelector has a limitation as said in the .h file:

 * Limitations:
 * Antialiasing will break this class. If your graphics card settings force
 * their use this class will return invalid results.

If the antialiasing technique is used, what result will be returned? Does it affect vtkPropPicker?