[vtkusers] VTK pipeline & rendering strategies

[David Lonie]

On Tue, Nov 29, 2016 at 12:21 AM, Andrea Gavana <andrea.gavana at gmail.com>
wrote:

> But beside the filters, I'm still puzzled by the actual call to Render
> that is taking up so much time. And the grid I have is not particularly big
> by industry standards, some grids can easily go up to millions of cells.
>

One thing that might explain the long render time is the delayed-execution
model of the VTK pipeline in ParaView. The filters will not be executed
until the renderer explicitly requests data during rendering, unless
Update() is called on the filter beforehand. So you may be seeing the
combined execution time of the filters and the renderer/mapper in your
results. Try calling Update explicitly on the filters and time that to make
sure you're measuring each filter's execution separately.

Another thing that can slow down rendering is translucent geometry.
Correctly composing translucent geometry requires rendering pieces in depth
ordering, and this requires multiple passes through the data. The higher
the 'depth complexity' of the scene, e.g. how many layer of geometry
contribute to each pixel, the more geometry passes are required.

HTH,
Dave
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