[vtkusers] Start-up performance of hardware renderers

[Simon ESNEAULT]

Hi Ian,

See this mail :
http://public.kitware.com/pipermail/vtkusers/2010-November/112994.html

and this bug report
http://vtk.org/Bug/view.php?id=11391

I bet it's the same "bug" that affect's you.
With an ATI card, the only solution you've got in VTK for a GPU volume
rendering is the vtkVolumeTextureMapper3D class, but you will need to hack a
little bit to make it work properly (fast). See instruction in the link
above.

Good luck, do not hesitate if you need some help.

Simon




On Mon, Jun 6, 2011 at 11:38, Ian Lindsay <ilindsay at insigniamedical.co.uk>wrote:

> Hi, I hope someone with a bit of experience with the hardware renderers
> in vtk can help me. Apologies in advance for the long post, but I want
> to give as much detail as possible.
>
> We are developing a medical imaging application which will visualise
> CT/MR data using various techniques - MIP, MPR, volume rendering etc. I
> am currently experimenting with the vtkVolumeTextureMapper3D class, and
> while its performance is great on an ATI Radeon 3870 once it has
> started, and even better on newer cards, it seems to take a long time to
> initialise. I am seeing ~20-25 seconds for a 250 slice CT set, each
> image being 512X512 pixels at 2 bytes per pixel. We are seeing 100% CPU
> usage on one CPU of a dual core Intel Core-2 duo, which would seem to
> suggest that the algorithm is not multi-threaded in this case if that is
> of any help. Doing a break while debugging seems to generally end up in
> the vtkVolumeTextureMapper3DComputeScalars function in
> vtkVolumeTextureMapper3D.cxx, in a loop that looks like it is doing some
> sort of re-sampling.
>
> The pipeline is a fairly standard one as far as I can see:
>  vtkImageData
> -> vtkImageChangeInformation
> -> vtkVolumeTextureMapper3D
> -> vtkVolume
> -> vtkRenderer
> -> vtkRenderWindow
>
> We also introduce a vtkImageFlip for flipped data sets (e.g. CT heads)
> to get them back to DICOM orientation before the volume mapper, but this
> seems to make very little difference.
>
> One point that may make a difference is that we are doing offscreen
> rendering due to our application architecture requirements, but we get
> very good performance with MPR implemented with vtkImageReslice, so I
> suspect this is not the issue.
>
> I have tried experienting with the SetUseCompressedTexture(true)
> setting, which seemed to make things a little more stable, I sometimes
> ended up with blank images, or strange lighting on occasions before, but
> this does not seem to help the initialisation time. I have also tried
> the vtkGPUVolumeRayCastMapper, but this seems to use features only
> supported by NVIDIA cards (correct me if this is wrong), whereas we have
> found our medical imaging displays work best with ATI cards, so we tend
> to use these in preference.
>
> Does anyone have any helpful advice on settings/pipeline layout or
> alternative ray casters that I could try?
>
> Thanks,
> Ian Lindsay
>
>
>
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Simon Esneault
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