[vtkusers] Picking questions

Sherwood, P (Paul) P.Sherwood at dl.ac.uk
Wed Oct 23 14:49:40 EDT 2002


thanks for this.

I have played around and ended up passing the
molecule and atom picked by declaring the observer with
something like

    # actor a represents atom at in molecule m
    a.AddObserver('PickEvent', \
         lambda obj,ev,s=self,mol=m,atom=at : s.mypick(mol,atom,obj,ev)

I still feel it looks like a rather complicated way of providing
some user data for when the pick event happens. It seems to work, but
if there is a nicer way I'd like to know!

thanks again


>>  -----Original Message-----
>>  From: Prabhu Ramachandran [mailto:prabhu at aero.iitm.ernet.in]
>>  Sent: 23 October 2002 18:08
>>  To: Sherwood, P (Paul)
>>  Cc: vtkusers at public.kitware.com
>>  Subject: Re: [vtkusers] Picking questions
>>  hi,
>>  >>>>> "PS" == P Sherwood <Sherwood> writes:
>>      PS> I am just experimenting with picking and I am unsure how to
>>      PS> efficiently work out which atom was picked. I am working in
>>      PS> Python.
>>      PS> I can identify the picked property (Actor) using
>>      PS> picker.GetPath().GetFirstNode(), by I am not sure 
>>  of the best
>>      PS> way to find out which atom in my model was picked. 
>>  Is there a
>>      PS> user data component of an actor I could set when it 
>>  is created
>>      PS> and access to indicate what it represents when it is picked?
>>  If you are using VTK 4.0+ then you can use observers to do this
>>  easily.  Here is a quick example using MayaVi's ivtk module (for
>>  convenience).
>>    from mayavi import ivtk
>>    import vtk
>>    cs = vtk.vtkConeSource()
>>    m = vtk.vtkPolyDataMapper()
>>    a = vtk.vtkActor()
>>    m.SetInput(cs.GetOutput())
>>    a.SetMapper(m)
>>    v = ivtk.viewer()
>>    v.AddActors(a)
>>    def test(obj, event):
>>       print "Event", event, "occured"
>>       print repr(obj)
>>    a.AddObserver('PickEvent', test)
>>  Now press 'p' on the viewer window near one of the vertices of the
>>  cone and see your test function in action.
>>      PS> Also, is there any way to pick multiple actors 
>>  using something
>>      PS> like the rubberband selection tools many programs use these
>>      PS> days?
>>  No clue if there is something to do this already but I guess you can
>>  write some code to do this.  However it might take some work.
>>  cheers,
>>  prabhu

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