[vtkusers] volume rendering performance

[Mark Wyszomierski]

That's really interesting, for me the ProjectedTetra was so time consuming I
ended up rendering only one slice of my volume so I could at least see some
output. I do have many variations in opacity, my dataset is of a chest (I
don't have much 'dead' space around the organs), so it sounds like this may
really be a bad use of ProjectedTetra.

All my output is interactive, fixed point/3d texture have been pretty decent
when it comes to responsiveness, except if the camera moves too close to the
volume. The ray cast mapper looks the 'nicest' but it really takes too long
to be used interactively for me. I was hoping that the responsiveness of
ProjectedTetra would be good once ready for display, but it actually had the
worst interactivity out of the bunch, even with one slice. Besides the
opacity issue, I believe the ray cast mapper etc have built in functions to
reduce the quality of the rendering while the user is interacting, which is
very nice.

Thanks for sharing your experience,
Mark




On 2/7/06, Randall Hand <randall.hand at gmail.com> wrote:
>
> The last dataset I used was a 512-cube, stored as a vtkImageData I
> believe.  One thing that greatly effects rendering time is the level of
> opacity you have.  in my case, I had large regions of the space that were
> going to be completely transparent (accumulated opacity = 0.0), with only
> a small fireball in the center to render.  If I adjusted my transfer
> function so that larger regions were rendered, then the render time
> increased.
>
> Using a fixed transfer function that rendered only the small portion of
> the dataset I wanted to see, the FixedPoint mapper was abysmal at about 30
> minutes per frame, and the ProjectedTetra mapper works in about 6 minutes
> (with the DataSetTriangleFilter time included).  All of my stuff is
> non-interactive, being dumped directly to PNG images on disk.
>
> On 2/7/06, Mark Wyszomierski <markww at gmail.com> wrote:
> >
> > Hi Randall, Faith,
> >
> > I gave vtkProjectedTetrahedraMapper a try for the first time today but I
> > experienced the longest render times with it out of any of the other
> > mappers. I'm wondering what your input data being rendered is? Mine is a
> > vtkImageData volume with dimensions of 256x256x56. The fixed point mapper or
> > 3d texture mapper give me the fastest results.
> >
> > Mark
> >
> >  On 2/6/06, Randall Hand <randall.hand at gmail.com > wrote:
> > >
> > > I think the best results will actually come from using the
> > > vtkProjectedTetrahedraMapper -
> > > http://www.vtk.org/doc/release/5.0/html/a01919.html
> > >
> > > I've pretty much tried them all.  The vtkVolumeRayCastMapper took
> > > about an hour to generate an image for me, the vtkFixedPointRayCastMapper
> > > cut it down to about 30 minutes.  The vtkProjectedTetrahedraMapper takes the
> > > cake, however, at a whopping 5 minutes.  Unfortunately, it does take alot
> > > more memory as it requires you to "tetrahedralize" your mesh.
> > >
> > > On 2/6/06, flin at enders.tch.harvard.edu <flin at enders.tch.harvard.edu >
> > > wrote:
> > > >
> > > > Hello all,
> > > >
> > > > I need some advice on how much imporvement the
> > > > vtkFixedPointVolumeRayCastMapper will make vs. regular
> > > > vtkVolumeRayCastMapper ?  I'm doing volume rendering of roughly
> > > > 250x80x150 voxels, and the speed is unacceptable.   Any suggestions
> > > > on how
> > > > to speed up?  Specifically, how to use hardware to accelerate it?
> > > >
> > > > Thanks.
> > > >
> > > > /faith
> > > >
> > > >
> > > > _______________________________________________
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> > >
> > >
> > >
> > > --
> > > Randall Hand
> > > Visualization Scientist,
> > > ERDC-MSRC Vicksburg, MS
> > > Homepage: http://www.yeraze.com
> > > _______________________________________________
> > > This is the private VTK discussion list.
> > > Please keep messages on-topic. Check the FAQ at:
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> > >
> > >
> >
>
>
> --
> Randall Hand
> Visualization Scientist,
> ERDC-MSRC Vicksburg, MS
> Homepage: http://www.yeraze.com
>
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