[vtkusers] Large Image, white rectangle

[Amy Henderson]

Hi Joe,

vtkImageActor uses texture mapping, so this type of problem with 
vtkImageActor is likely a problem with texture mapping.  So as James said, 
the texture size limit of your graphics card is probably the issue.

- Amy

At 12:21 PM 1/6/2004 -0800, Joe Miller wrote:
>Hi James,
>
>Thanks for the quick reply. Though I don't think I
>clearly stated my problem. The problem I'm having
>isn't with texture maps its with the image actor. When
>I read in an image 2000x2000 (that's an approximated
>value its around there though) pts or greater and try
>to just render the image actor I get a white rectangle
>instead of the 2d image.
>
>I had seen another message posted that had described a
>similar problems with texture maps. I was wondering if
>hardware limitations (to which my Sun Ultra 5 has
>many) were the cause the image actor couldn't display.
>Though the texture map problem may have been a red
>herring all together.
>
>Anyway, splitting the image is something I may be
>stuck considering. Though if there are any other
>thoughts, I'm still open to suggestions.
>
>Thanks again for your time.
>
>-joe
>
>--- James Urquhart <j_urquhart at btinternet.com> wrote:
> > On Tuesday 06 January 2004 4:02 pm, Joe Miller
> > wrote:
> > > Hi,
> > >
> > > I'm new to VTK and trying to read in and display
> > large
> > > 2D images (2000 x 2000). However, when I try and
> > > render the image all I get is a white rectangle. A
> > > simple program I wrote
> >
> > > I noticed in the archive there were a few mentions
> > of
> > > texture maps having similar problems. They
> > described a
> > > hardware issue that the hardware can only handle
> > > texture maps of certain proportions. I was
> > wondering
> > > if anyone knew if I was experiencing the same
> > problem
> > > and had any suggestsions of a workaround.
> >
> > Joe,
> >
> > From what i can see on the net, there appears to be
> > a texture size limit for
> > opengl on some graphics cards.
> > Usually the limit is in the 2048x2048 +- range.
> > Also remember that alot of graphics cards only like
> > textures with dimensions
> > of the power 2. e.g 16x16, 32x32, 256x256, 512x512
> > ...
> > Another thing to consider is the amount of memory on
> > the video card. Though
> > these days, cards typically have 64 / 128mb +, which
> > is plenty for your
> > typical 3d app. (at least i *hope*)
> >
> > You could try splitting your image up into smaller
> > segments, and mapping each
> > segment onto another polygon. You should easily be
> > able to keep the texture
> > seamless :)
> >
> > e.g for a 2048x2048 texture :
> >   Have 16 quad's, each representing a 512x512 block
> > of the image. (4 along the
> > top, 4 along the bottom, 4*4).
> >
> > -James
> >
> >
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