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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I remember now what it was I really wanted to say ...<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Inside the streamtracer/particle tracer code, the integrators like RK4 make many Get requests for the interpolated velocity, the requests are refined iteratively
and then the final interpolated position (cell+parametric coords) is used to get all the other scalars.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">So when implementing the abstract interpolation base class,, it’d be well to consider that it may be required to operate at the top level (like the current
probe filter and your image interpolation) where you simply loop over N points and compute the interpolated values<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">but it may also be called N times with a ‘quick look’ intention using as much cached info as possible, followed by the final call where we want the interpolated
values for all vars/scalars.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The interpolatedvelocityfield stuff has methods to find the parametric weights – and then later to use these weights to interpolate all scalars – if you follow
me. kind of break things up a bit so that the full calculation is not done every time.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">loop N times getting one field only, (velocity here)<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Reuse the weights from the best Get,<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">to Get all the other scalars using those weights.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">+ more tweaks for the caching stuff.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The more I write, the more I realize it will mess up your class to try to accommodate any of this.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">JB
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Additionally, the original implementation used code like<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">GetVelocity(x,y,z) and on every single access, the interpolation internally ran<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">GetPointData()->GetArray(VelocityArrayName) and then interpolating inside that field array<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">and was actually spending a huge amount of time inside the array lookup (as much as inside the parametric weight computation).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">so we want to avoid<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">GetValue(x,y,x,char *fieldname)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">and encourage<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">GetValue(x,y,x,vtkDataArray *)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">but ideally<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">template<T> GetValue(x,y,x,T *) for float/double etc arrays
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">which means we end up with<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">template<T> GetValue(x,y,x,T *, vtkIdType CellId, double *weights, etc etc)
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">but perhaps some of the concrete strategies can implement these and classes requiring these more sophisticated interpolators can ask for the strategies directly
rather than the abstract base ..<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Sorry for ranting on.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> David Gobbi [mailto:david.gobbi@gmail.com]
<br>
<b>Sent:</b> 06 July 2011 15:52<br>
<b>To:</b> Biddiscombe, John A.<br>
<b>Cc:</b> VTK Developers<br>
<b>Subject:</b> Re: [vtk-developers] A vtkDataSampler and image interpolation<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Thanks, John. This is the sort of info that I'm looking for, i.e. details about how the interface should specify what arrays to use as input, and what arrays to generate as output. All the other info, meaning
the use cases and specific implementations, is useful as evidence that a strategy-based approach to interpolation is desirable.<br>
<br>
- David<br>
<br>
<o:p></o:p></p>
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<p class="MsoNormal">On Wed, Jul 6, 2011 at 2:59 AM, Biddiscombe, John A. <<a href="mailto:biddisco@cscs.ch">biddisco@cscs.ch</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">>><br>
virtual void vtkDataSampler::SamplePoints(vtkPoints *points, vtkDataArray *outputScalars);<br>
<<<o:p></o:p></p>
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<p class="MsoNormal">it's worse though because we might need all scalars, not just one<br>
<br>
virtual void vtkDataSampler::SamplePoints(vtkPoints *points, vtkDataSetAttributes *blah-de-blah);<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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