[vtkusers] Update Subimage (glTexSubImage3D, glTexSubImage2D)

[David Gobbi]

Hi Francois, Jacob,

The vtkImageActor class uses glTexSubImage2D, specifically so that
images that aren't a power of two can be efficiently rendered (and
re-rendered).  However, you cannot tell vtkImageActor to only update a
region of its input image, it always updates the entire displayed
slice.

 - David


On 6/5/07, Francois Bertel <francois.bertel at kitware.com> wrote:
> Somebody else probably knows more than me about that, but I think there is no mechanism at the vtkImageData level or in the pipeline level to tell that only one sub-block of a vtkImageData has changed.
> There is some update extent versus whole extent mechanism but I think it is for streaming or for parallel computation.
>
> In addition, if the texture does not have dimensions equal to a power of two, loading a texture requires some adaptation that prevents a quick subimage update.
>
> Jacob Foshee wrote:
> > Hello, all,
> >
> > Does VTK support updating a subimage via glTexSubImage*D?
> >
> > Searching the code, I find this only in FreeType (FTTextureGlyph.cpp)
> > and in vtkOpenGLImageActor::Load(vtkRenderer *ren) .  It does not appear
> > to be a general option for updating part of an existing texture.
> >
> > Is there anyone using VTK in this way?  I need high-speed update of
> > texture memory.
> >
> > Thanks!
> > Jacob
> >
> >
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