[vtk-developers] Why is BuildShaders() continuously being called?

[Ken Martin]

When  GetNeedToRebuildShaders returns true. Which roughly is

  if (cellBO.Program == 0 ||
      cellBO.ShaderSourceTime < this->GetMTime() ||
      cellBO.ShaderSourceTime < actor->GetMTime() ||
      cellBO.ShaderSourceTime < this->CurrentInput->GetMTime() ||
      cellBO.ShaderSourceTime < this->SelectionStateChanged ||
      cellBO.ShaderSourceTime < renderPassMTime ||
      cellBO.ShaderSourceTime < this->LightComplexityChanged[&cellBO])
    {
    return true;
    }

So if the main points are if you are modifying the actor, mapper, or your
data. If one of those is being modified every frame then let me know the
use case and we can see if the current test is being too aggressive etc.

Thanks
Ken




On Fri, Sep 9, 2016 at 5:47 PM, Milef, Nicholas Boris <milefn at rpi.edu>
wrote:

> Under what conditions are shaders actually rebuilt? This seems to be the
> source of my performance issues and I need to know how to avoid this. The
> function I'm referring to is in vtkOpenGLPolyDataMapper(). It seems that
> they get rebuilt when an object gets modified, is this true?
>
> Thanks,
> Nick
>
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Ken Martin PhD
Chairman & CFO
Kitware Inc.
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