[vtk-developers] parallel surface lic broken in opengl 2

[Burlen Loring]

Great, sounds like you guys are aware of the issues. Thanks for working 
on it!

On 03/01/2016 10:38 AM, Ken Martin wrote:
> I believe there are 4 main LICs in VTK OpenGL2, serial, parallel, 
> serial + composite_dataset, parallel + composite_dataset. I believe 
> the first three work and I think trashed pixels have been fixed 
> recently, the VTK tests all pass. yay!
>
> The parallel + composite_dataset case is known to be broken, more 
> specifically the class does not exist. PV needs this class in parallel 
> and I think it falls back to the serial implementation as that class 
> has been written which is why you see boundary issues.
>
> My gut feeling is that instead of writing that class, the LIC code 
> should be reworked as a render pass that gets assigned to mappers. 
> That way adding lic to a mapper is fairly easy. The way I converted 
> the original code to OpenGL2 combines the LIC complexity into the 
> middle of the mapper complexity which is a bad mix especially for the 
> parallel + composite_dataset case.
>
> Maybe it is easier than I think, but currently I suspect it would take 
> a few weeks of dedicated effort which is why it is still in the queue.
>
>
>
>
> On Tue, Mar 1, 2016 at 12:50 PM, Burlen Loring 
> <burlen.loring at gmail.com <mailto:burlen.loring at gmail.com>> wrote:
>
>     Hi All,
>
>     Writing to report that in latest version of ParaView the surface
>     lic is broken with the OpenGL2 back end. I experimented with it
>     using PV5 an nvidia gtx 980 with fairly recent driver, and saw a
>     number of issues, including completely "trashed" pixels and when
>     rendering in parallel one can see "lines" at process boundaries as
>     if the algorithm is serial.
>
>     These regression are a shame because it took quite a lot of effort
>     to correctly parallelize it, and make it work reliably across a
>     wide spectrum of os,gl, and device variations. There is an
>     explanation of the parallel algorithm linked below. Hopefully
>     those who are working on porting to opengl 2 are aware of and will
>     take a look at these regressions.
>
>     Note, that all of the surface LIC classes live VTK but because
>     IceT and the compositing classes all live in ParaView, the ctest
>     for parallel operation are in ParaView. So another question is,
>     given the importance of parallel rendering, should IceT and
>     parallel rendering capability be included in VTK?
>
>     Burlen
>
>     https://github.com/burlen/astronum2014/blob/master/paper/loring-astronum-2014.pdf
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> -- 
> Ken Martin PhD
> Chairman & CFO
> Kitware Inc.
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