[vtkusers] Opacity adjustment of the image data region

[staison]

Hi,

I want to segment the area and control its opacity during volume rendering
and image slicing. Is there any common solution?

I have the dicom data and mask (binary image) as input. I tried to find
something similar to MaskInput of vtkGPUVolumeRayCastMapper with the control
of binary mask opacity but unsuccessfully.

I experimented with 2 component image data (1 component - color, 2 -
opacity). Set mock scalar value (e.g +9999) for the segmented region (mask)
in the second component to control its opacity. But
vtkGPUVolumeRayCastMapper is not support it,
vtkFixedPointVolumeRayCastMapper does it slow, memory overloading and with
strange artifacts (see attached image), vtkVolumeTextureMapper3D does it
slow and uses even more memory and without any explicit artifacts.

I looked at multi-volume rendering but have no idea how to do it with VTK. I
find out that NCI did a vtk GPU ray caster that supports multiple volumes
(http://vtk.1045678.n5.nabble.com/Multi-Volume-RayCasting-td5086611.html).
Is there any examples of multi-volume rendering?

Adding transparency mask for a vtkImageData displayed with a vtkImageActor
was discussed in
http://vtk.1045678.n5.nabble.com/Adding-a-transparency-mask-to-an-image-td2851112.html.
But I just want to set the opacity of masked pixels without applying any
color and avoiding of using secondary actor.



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