[vtkusers] vtkGPUVolumeRayCastMapper: Updateing ImageData after first Rendering?

[Aashish Chaudhary]

Hi Willy,

The first call is done to get the min/max for transfer functions (without
looking into code). I do not remember if your data is changing, if it does
it will trigger min/max computation. Are you providing your own transfer
functions?

- Aashish

On Mon, Feb 20, 2017 at 7:59 AM Willy <Wiggerl at linhuber.info> wrote:

> I found a bit information about the 1m 29 s wait time. The first call of
> vtkOpenGLGPUVolumeRayCastMapper::GPURender calls
> vtkVolumeTexture::LoadVolume and that calls vtkDataArray::GetRange and that
> method loops through my 3GB scalar data and calls each time min and max (to
> get the min and max value of all values). Can i prevent vtk from doing
> that?
> Why does vtk even calculate that? Does vtk maybe want to scale the
> greyvalues bewenn min and max? Maybe i can disable that somehow?
>
> Moreover i tested a application named ParaView (ParaView uses vtk too).
> ParaView does not wait 1m29s. It seems like it is not neccessary to
> calculate min and max.
>
>
>
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