[vtkusers] Speed/vtkImageData

[David Gobbi]

Hi Ted,

If you set the vtkFloatArray for your ImageData directly (i.e. if your
ImageData does not have a Source) then the Update() that I mentioned
in the last email will not speed up the render, nor will it significantly
slow it down.

If you're dealing with a 3D image, maybe changing the FloatArray is what
is slowing things down rather than the rendering.

 - David


On Thu, 1 Apr 2004, Ted Vu wrote:

> Hi David thanks very much for your response,
> I already have a good graphics card on my computer.. so this shouldnt be the
> problem..
> Actually the values in the vtkFloatArray which I input into my ImageData is
> changed before every render, so to update the changes I was calling
>    ImageData->Modified()
> before every call to Render()..
> (and also
>    FloatArray->SetVoidArray( array, NumXpoints*NumYpoints, 1 )
> right after my 'array' is updated with new values.. this is the FloatArray
> that is used by my ImageData)
>
> So if I insert the following functions as well, then woudnt this slow things
> down..?
> ImageData->UpdateInformation();
> ImageData->SetUpdateExtent(ImageData->GetWholeExtent());
> ImageData->Update();
>
> I've used ImageViewer before and this seems pretty fast, but I have 3 actors
> so this is why I'm not using this class..
>
> Okay thank-you again for your response!
> Ted
>
>
> >From: David Gobbi <dgobbi at imaging.robarts.ca>
> >To: Ted Vu <lost_bits1110 at hotmail.com>
> >CC: vtkusers at vtk.org
> >Subject: Re: [vtkusers] Speed/vtkImageData
> >Date: Thu, 1 Apr 2004 14:07:10 -0500 (EST)
> >
> >Hi Ted,
> >
> >Make sure the whole of the ImageData has been updated.  I suspect
> >that the reason things are slow is that it is continuously re-reading
> >the data from disk, either that or it is continuously re-executing
> >upstream portions of the pipeline.
> >
> >To update the whole ImageData:
> >ImageData->UpdateInformation();
> >ImageData->SetUpdateExtent(ImageData->GetWholeExtent());
> >ImageData->Update();
> >
> >If this is the first time that the ImageData has been updated,
> >you can just do ImageData->Update() and skip the rest.
> >
> >Also, since ImageActor renders the image via texture maps, make sure
> >that you have a good 3D graphics card in your computer.
> >
> >  - David
> >
> >
> >On Thu, 1 Apr 2004, Ted Vu wrote:
> >
> > > Hi
> > > Is there any way I can speed up rendering of 2D vtkImageData?
> > >
> > > My pipeline is
> > >
> > > ImageData -> ImageMapToColors -> ImageActor
> > >
> > > I have 3 of these ImageData's which appear on one Renderer
> > >
> > > Can I somehow use LODActor do you think?
> > >
> > > Thanks!
> > >
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