[vtkusers] Smooth label-map volume rendering

[Sankhesh Jhaveri]

Hi Andras,

Note that the vtkGPUVolumeRayCastMapper already supports labeled data
rendering.

Take a look at TestGPURayCastCompositeMask and
TestGPURayCastCompositeMaskBlend.

Sankhesh​

On Thu, Jun 7, 2018 at 12:08 PM Andras Lasso <lasso at queensu.ca> wrote:

> I would be interested in a good solution to this, too.
>
>
>
> In 3d Slicer, we’ve been using flying edges filter, which creates usable
> (non-blocky) surfaces very quickly (suitable for interactive editing). The
> limitation is that we still need a smoothing filter to avoid all staircase
> artifacts, and that it increases update time by about a magnitude.
>
>
>
> We’ve been evaluating using multi-volume rendering for displaying
> segmentation in 3D, to achieve faster updates and nicer transparent
> renderings. Multi-volume rendering is good because we can apply Gaussian
> smoothing on each input volume to get correctly reconstructed (non-blocky)
> surface and we can display overlapping segments. However, this Gaussian
> smoothing takes some time (still competitive with surface smoothing) and
> multi-volume renderer does not support shading yet (this is the blocking
> issue right now).
>
>
>
> Andras
>
>
>
> *From:* vtkusers <vtkusers-bounces at public.kitware.com> * On Behalf Of *Bertram
> Sabrowsky-Hirsch
> *Sent:* Thursday, June 7, 2018 3:54 AM
> *To:* vtkusers at vtk.org
> *Subject:* [vtkusers] Smooth label-map volume rendering
>
>
>
> Hi all,
>
>
>
> I am working with volume data before and after a classification algorithm.
>
> The input volume has ushort intensity values, the output volume is a
> label-map where the values indicate each voxels class/label (background=0,
> vessel=1, aneurysm=2, …).
>
>
>
> I am visualizing the input volume with a opacity transfer function that
> simulates a threshold filter (e.g. control points: 799=0.0, 800=1.0) and
> the result is a nice and smooth visualization of the volume.
>
>
>
> However, the output volume has this blocky Minecraft style effect. The
> opacity transfer function has the control points: 0=0.0, 1=1.0 and I use
> the color transfer function to distinguish the classes/labels.
>
> Is there a way to visualize the output volume in a similar way as the
> input volume? I considered generating iso-surface meshes and smooth those,
> but this is not really an option. I also don’t really understand why this
> is an issue because the
>
> Input volume is also rendered with a distance of 1 between the two opacity
> thresholds. Are the volumes handled differently by vtk and how?
>
>
>
> Input volume:
>
>
>
> Output volume:
>
>
>
> Kind regards,
>
> Bertram
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-- 
Sankhesh Jhaveri *Sr. Research & Development Engineer* | Kitware
<http://www.kitware.com/> | (518) 881-4417
​
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