[vtkusers] OK so does ANYONE use the vtkImageTracerWidget?

[Mark Wyszomierski]

Dean,

I worked with this a bit more, I have two questions if you have time:

1) Right now after the enclosure is drawn, I am storing all the points using:

        GetPath(vtkPolyData);

When trying to restore the points of the enclosure later on, there
doesn't seem to be any 'SetPath()' function, we have to use
InitializeHandles(). The problem is that there may be hundreds of
points that make up an enclosure, and now all of them will be turned
into handles which can be really slow. For instance, if you just draw
a free-hand enclosure, there's only one handle. I can't find a way to
restore that enclosure with one handle but many non-handle points.

2) To initialize a 'NULL' enclosure, it looks like we need to push on
at least two dummy points, otherwise the line connection code isn't
generated. For now I'm doing:

        p->InsertNextPoint(0, 0, 0);
        p->InsertNextPoint(0, 0, 0);

I checked the condition inside InitializeHandles() and it seems at
least two handles are necessary (otherwise previous line geometry
isn't reset).

After you suggested SetProjectionPosition(), my example is working as
expected, I will post it if anyone is still interested. The widget is
great, just wondering if there's some way around #1 to speed it up a
little,

Thanks,
Mark



On 11/5/07, Dean Inglis <dean.inglis at sympatico.ca> wrote:
> A couple of points on using vtkImageTracerWidget:
>
> 1) InitializeHandles requires that the vtkPoints be non-NULL
> and that there be n>0 points
> 2) if you change the slice position, then you have to
> tell the widget where you want to place points onto:
> (e.g. from Examples/GUI/Tcl/ImageTracerwidget.tcl)
>  itw ProjectToPlaneOn
>  itw SetProjectionNormalToXAxes
>  itw SetProjectionPosition $pos
>
> If you just change the slice position using vtkImageActor
> to view slices in a volume and not the slice
> orientation, then SetProjectionPosition will update
> the coordinates of all the handles of the widget.
>
> Kent, as for your current problem:
>
> >What isn't happening right now: If I switch to an untraced slice, I
> >call InitializeHandles() with a zero length set of points, but this
> >doesn't in fact get rid of the currently visualized trace.
>
> I didn't design the tracer to work this way, but if you
> want a work-around for now, just send in a vtkPoints
> with one point with coords of the center of the current
> image slice.  This should show one handle signifying
> to the user to start tracing.  e.g.:
>
> vtkPoints* pt = vtkPoints::New();
> pt->InsertNextPoint(0,0,0);
> // set the widget to have one handle
> widget->InitializeHandles(pt);
> // this should force the first handle to lie at the center of
> // the bounds of the image plane
> widget->PlaceWidget(myImageActor->GetBounds());
> // if the slices are x-y planes
> widget->SetProjectionPosition(myImageActor->GetBounds()[4]);
>
>
> Another option would be to use the latest cvs
> vtkContourWidget since I recently
> modified it to take a NULL vtkPolyData in to Initialize
> the widget to its starting state. You can draw with either
> straight line segments between placed handles or
> have it interpolate a higher order curve between them.
> vtkCntourWidgte will not let you "trace" continuously though.
>
> HTH,
> Dean
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