[vtkusers] Large Image, white rectangle

[James Urquhart]

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