[vtkusers] vtkImageReslice speed

[alex. gouaillard]

> Until very recently, VTK strictly followed the OpenGL 1.1 standard and 
> used no extensions.  The reason for this was maintenance and testing, 
> particularly on Windows since Microsoft only guarantees conformance with 
> OpenGL 1.1.  As soon as new code paths are put in to take advantage of 
> OpenGL extensions that may or may not be present on a system, you have 
> to run tests both on machines that have the extensions, and on ones that 
> don't.
> 
> I suspect that Kitware is more open to allowing OpenGL extensions now 
> than they were before, and speaking for myself, I think this would be a 
> great addition to vtkOpenGLTexture.
> 
>  - David

I'm not familiar with the windows implementation of OpenGl, but it seems
strange there are stuck with 1.1 when 1.2, 1.3, 1.4, 1.5 and now 2.0
have been out for years. Indeed on openGL.org they only list 1.1 for
windows while admitting that drivers might support more advanced
versions ...

Yeah, I know extension testing can be  painfull, to say the less. Plus
you don't really wanna use an extension that OpenGl would support but
that your hardware wouldn't (software fallback are so damm slow).

As for extensions, everything beginning by ARB is not an extension
anymore but a feature of the core. This texture_non_power_of_two has
been included in the core since 1.4 (2000 ?).

I saw shaders where implemented in vtk 5.0, what about the rest of
OpenGl 2.0 APIs ?

alex