[vtkusers] vtkImagePlaneWidget Transparency/Windowing Problems

[David Kushner]

Brilliant, thanks Miro. Your suggestion worked well. I was hoping to be
able to map 0-values (pure black) to total transparency while applying the
0.5 opacity to the remaining image. Is there a way to accomplish this
specifically? This is just icing on the cake, I quite like the result I get
with your suggestion but the background is still occluding some details of
the planes behind.

Thanks again!

On Fri, Apr 24, 2015 at 3:02 PM, Miroslav Drahos <mdrahos at thinksurgical.com>
wrote:

> Try
> planeWidget->GetTexturePlaneProperty()->SetOpacity(0.5);
>
> Best,
> Miro
>
> ________________________________________
> From: vtkusers [vtkusers-bounces at vtk.org] On Behalf Of David Kushner [
> root at davidkushner.me]
> Sent: Friday, April 24, 2015 2:18 PM
> To: vtkusers at vtk.org
> Subject: [vtkusers] vtkImagePlaneWidget Transparency/Windowing Problems
>
> I'm currently building an application based heavily on the source provided
> in the QtVTKRenderWindows example (
> https://github.com/Kitware/VTK/blob/master/Examples/GUI/Qt/FourPaneViewer/QtVTKRenderWindows.cxx)
> using VTK 6.1. The only appreciable difference between my implementation
> and the one laid out in the example is the fact that, rather than using the
> vtkDICOMImageReader class, I'm loading our DICOM CT image in with ITK 4.8
> and then converting it to the corresponding VTK image format using the
> itk::ImageToVTKImageFilter. I'm not sure if this is relevant to the issue
> I'm having, but I figure it couldn't hurt.
>
> The issue is, though the image loads and renders just fine, the windowing
> applied to the image does not display transparency for out-of-window values
> as I would expect (and maybe this expectation is completely silly). The
> pixel type I'm using for the images, since they are CT scans, is `signed
> short`. The result I am seeing when I start my application is this:
>
> [cid:ii_14ced4775ccffd82]
> (http://i.imgur.com/vRkN0Ak.png)
>
> Apologies if it is inappropriate to paste images inline or at all. As you
> can see, though the background values contained in the CT slice solid
> black, they are not exhibiting transparency as I would expect (or hope to
> achieve). Would anyone have some advice on how to achieve a transparency
> effect with this setup? I've tried a number of things from fiddling with
> the windowing of the plane widgets, the windowing values and color map of
> the renderer itself and then converting the image to an RGBA image before
> sending it on to the plane widgets. None of these seemed to have any effect
> on the outcome; the planes still rendered as opaque.
>
> Any help would be GREATLY appreciated. It seems to me to be such a simple
> task yet I've mired myself in the complexities of ITK/VTK.
>
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