[vtkusers] Mesh cutting using freehand curve

[Miguel Sotaquira]

Hi Goodwin,

The filter vtkSelectPolyData doesn't require a closed loop to select the
region inside/outside the polygonal mesh? In my case I actually don't have
a closed contour, just a freehand line obtained using vtkContourWidget.

I was checking the documentation and there's this vtkImplicitSelectionLoop
that would be useful, although - again - it seems that only works with
closed contours. Isn't there something similar to vtkImplicitSelectionLoop
but that works with open selections?

Thanks again!
Miguel

On Tue, May 22, 2012 at 8:16 AM, Goodwin Lawlor <
goodwin.lawlor.lists at gmail.com> wrote:

> Hi Miguel,
>
> Try out this pipeline:
> (in Tcl but it's the same idea in any language)
>
>   vtkPoints selectionPoints
>     selectionPoints InsertNextPoint 1.0 1.0 1.0
> # etc...
>
>   vtkSelectPolyData select
>     select SetLoop selectionPoints
> # connect your data here
>     select SetInputConnection [mydataFilter GetOutputPort]
>     select GenerateSelectionScalarsOn
>     select SetSelectionModeToLargestRegion;
>
>   vtkClipPolyData selectclip
>     selectclip SetInputConnection [select GetOutputPort]
>     selectclip SetValue 0.0
>
> It's not 100% robust but works for most meshes that have well behaved
> topology...
>
> hth
>
> Goodwin
>
> On Tue, May 22, 2012 at 4:45 AM, Miguel Sotaquira <msotaquira at gmail.com>wrote:
>
>> Hi everyone!
>>
>> I have a 3D manifold mesh and I want to be able to cut it using a
>> freehand (drawn by user) contour. An example of such a mesh and the contour
>> drawn by the user is shown in this image:
>> http://postimage.org/image/sbnmcoodj/. By cutting I mean generating a 3D
>> surface from the freehand contour and then splitting the mesh in two parts.
>>
>> Up to this point I've came up with this workflow for generating the
>> freehand contour: vtkContourWidget -> vtkPolygonalSurfacePointPlacer. With
>> this approach I'm able to draw the contour on the polydata mesh (see
>> previous figure) and extract the set of contour point coordinates.
>>
>> However I'm lost from this point:
>> - How to generate the 3D cutting surface?
>> - Which would be the most adequate class to perform the cutting:
>> vtkClipPolyData, vtkCutter, vtkExtractPolyDataGeometry?
>> - In any of the previous classes I need a vtkImplicitFunction. How to
>> define a vtkImplicitFunction using the 3D cutting surface?
>>
>> Thanks for any suggestions,
>> Miguel
>>
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