[vtkusers] Volume Rendering Performance With Two Volumes

[Sankhesh Jhaveri]

Just so I understand correctly, you have two volumes in the same viewport
and are interacting with each separately. Is that the case? Or do you have
two different viewports? Do you see the same issue on a different graphics
card?

As far as performance, I agree if you’re not changing any other property on
the volume, viewport size and image sample distance should be the only
factors affecting rendering.
​

On Wed, Mar 21, 2018 at 10:36 AM ianl <ilindsay at insigniamedical.co.uk>
wrote:

> Just to be clear, I am interacting with each volume in turn for a few
> seconds
> each. It appears that one of the volumes gets cached onto the card and is
> performant, but not the other, no matter how much I interact with it.
>
> I have done some more experimentation, and down sampling the volumes makes
> a
> significant improvement to performance. This seems to imply some swapping
> on/off is going on. Incidentally, GPU-Z shows plenty of GPU RAM left
> (~700MB), but I don't know how accurate this is and of course it does not
> give me any idea how fragmented it is.
>
> Am I correct in assuming that once the volume data texture is loaded into
> GPU memory, then performance should only depend on
> ImageSampleDistance/viewport size i.e. the number of rays cast and
> SampleDistance i.e. the sample spacing - (in mm?) along the ray? Having
> less
> data at a wider spacing to sample through should not make a difference to
> performance, only quality - or is this a gross simplification.
>
> Thanks,
> Ian
>
>
>
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-- 
Sankhesh Jhaveri *Sr. Research & Development Engineer* | Kitware
<http://www.kitware.com/> | (518) 881-4417
​
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