[vtkusers] Update Subimage (glTexSubImage3D, glTexSubImage2D)

[Francois Bertel]

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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