[vtk-developers] Performance issue regarding vtkOpenGLGlyph3DMapper with large number of vtkDatasets

[David Thompson]

> You are using 258 mappers and actors right to go with the 258 datasets?

He's using 1 glyphmapper to glyph a multiblock dataset with 258 top-level blocks (i.e., there are 258 glyph sources).

	David

> 
> On Mon, Apr 9, 2018 at 11:36 AM, David Thompson <david.thompson at kitware.com> wrote:
> Hi Haocheng,
> 
> > I have a use case that I want to glyph several hundreds of vtkDatasets. However, the frame rate becomes super slow since vtkOpenGLyph3DMapper would call rebuildstructures function for each dataset. With 258 vtkDatasets, it takes more than 4 seconds to render one frame and spends 52% of the time doing rebuilding stuff(Rebuilding the structure 258 times even though nothing new!). I'm thinking to remove Line 515 in /Rendering/OpenGL2/vtkOpenGLGlyph3DMapper.cxx and pass a flag instead to trigger the rebuilding if a new color is assigned.
> 
> I'm not sure that change would not be enough to guarantee that the vtkOpenGLGlyph3DMapper::vtkOpenGLGlyph3DMapperEntry objects are kept up to date.
> 
> It might be better to understand why the mapper's MTime is being updated every render. If we can't use the mapper's MTime, then we should probably add a new MTime member to the mapper that gets modified when things that *do* matter (like block color changes) occur.
> 
>         David
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> Ken Martin PhD
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