View source for VTK/Replacing vtkMultiThreader with vtkSMPTools

The following VTK classes rely on vtkMultiThreader, and many of them can be converted to using vtkSMPTools instead:

 Common/ExecutionModel/vtkThreadedImageAlgorithm.cxx
 Filters/FlowPaths/vtkStreamer.cxx
 Filters/Hybrid/vtkImplicitModeller.cxx
 Rendering/Core/vtkImageMapper3D.cxx
 Rendering/Volume/vtkEncodedGradientEstimator.cxx
 Rendering/Volume/vtkFixedPointVolumeRayCastMapper.cxx
 Rendering/Volume/vtkUnstructuredGridVolumeRayCastMapper.cxx
 Rendering/Volume/vtkVolumeRayCastMapper.cxx
 Geovis/Core/vtkGeoSource.cxx
 IO/Video/vtkVideoSource.cxx
 Web/Core/vtkDataEncoder.cxx

== Algorithms that can be converted to vtkSMPTools ==

=== vtkThreadedImageAlgorithm ===

This is the base class for nearly all the VTK imaging filters, and it is probably the most difficult one to convert.  Its conversion is the highest priority.

=== vtkStreamer ===

This is the base class for vtkStreamLine.

=== vtkImplicitModeller ===

Uses multithreading for its internal structured data processing.

=== vtkImageMapper3D ===

Uses multithreading for its color mapping operations.

=== vtkEncodedGradientEstimator ===

Base class for vtkFiniteDifferenceGradientEstimator, which uses multithreading to compute image gradients.

=== vtkVolumeRayCastMapper et al. ===

All of the CPU-based ray cast mappers divide the ray casting among the threads.

== Algorithms that cannot be converted to vtkSMPTools ==

=== vtkGeoSource ===

This is not an SMP algorithm, it uses vtkMultiThreader to create a single background thread.

=== vtkVideoSource ===

This is not an SMP algorithm, it uses vtkMultiThreader to create a single background thread.

=== vtkDataEncoder ===

This is not an SMP algorithm, it uses vtkMultiThreader to create a single background thread.