On Thu, 2017-04-06 at 10:27 +0200, Gert Wollny wrote: > Hello all, > > I just drop this here for future reference.
Thanks for looking into it and summarizing your findings. > I've experimented a bit with VTK-7.1 and among other, minor issues I > came across the problem that VTK now defaults to, and, hence, > encourages the use of, a new renderer backend, called OpenGL2 that > requires an OpenGL 3.2 context. The old OpenGL renderer is still > available in the code, but when compiling VTK one can only enable one > or the other. Ack. > Now, OpenGL specifies a compatibility profile that would provide the > legacy fixed function interface also with the new >=3.2 context, but > Mesa doesn't implement it, which means, code written against the old > style OpenGL API will not run properly when a 3.2 OpenGL context is > used (as required by the VTK OpenGL2 backend), even if the > incompatibilities between the VTK renderer class interfaces could be > patched. > > Also, code using the new renderer will not run on older graphics > hardware, since VTK then simply rejects pre-OpenGL 3.0 contexts. Well, I guess we will have to draw a line in the sand at some point about old hardware compatibility. Are there that many people running something as intensive as paraview on a very old laptop, I wonder? > One example that uses VTK, but it also has lots of old-style OpenGL > code in it is ginkgocadx, which means it can not run properly with VTK > with the new renderer is enabled. ginkgocadx has been abandoned by > upstream, and I started to maintain it and try to keep the code up to > date. The last few days I tried to port it to OpenGL >= 3.2, but it is > a big task, since toe code is littered with old-style openGL, so I > don't really see it being done, and I guess it is similar for other > projects that use VTK. I could imagine that even for software that is > actively maintained the developers may be reluctant to switch to the > new renderer if it contains too much non-VTK OpenGL code (I checked, > and at least with version 3.4 itksnap also uses some direct calls to > old-style OpenGL). > > On the other hand we can expect that some software will start to rely > on the new OpenGL2 renderer at which point we have a problem if we > don't want to keep two versions of VTK in the archives. I wonder whether we could keep VTK-6 for projects using the old API and force VTK-7-only projects to use the new one? VTK-6 and VTK-7 should be co-installable, right? Ghis
