The input doesn't have to be a polydata and usually won't be a polydata so it won't have normals already computed. if compute scalars is on then all the arrays are passed from the input to the output but if compute scalars is off then all but the array selected for contouring will be passed to the output.<br>
<br><div class="gmail_quote">On Wed, Aug 15, 2012 at 1:37 PM, Aashish Chaudhary <span dir="ltr"><<a href="mailto:aashish.chaudhary@kitware.com" target="_blank">aashish.chaudhary@kitware.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
May be it is obvious, but why we don't compute normal's for<br>
vtkPolyData in the first place? If the input has normal's array, then<br>
I would assume that output should have normal's by default.<br>
<div><div class="h5"><br>
<br>
On Wed, Aug 15, 2012 at 12:01 PM, Andy Bauer <<a href="mailto:andy.bauer@kitware.com">andy.bauer@kitware.com</a>> wrote:<br>
> I'd like to change ParaView's default behavior of the contour filter.<br>
> Currently the default is to compute normals and not compute gradients or<br>
> scalars. These defaults are only used for structured data sets (i.e.<br>
> vtkStructuredGrid, vtkImageData, and vtkRectilinearGrid) and are not options<br>
> when isosurfacing for vtkPolyData or vtkUnstructuredGrids. When the input<br>
> data set is a multiblock data set that contains both structured and<br>
> unstructured data sets the output for the current code results in a<br>
> multiblock data set with partial arrays (Normals for the structured data<br>
> sets and the contoured variable for the unstructured data sets). The change<br>
> I'd like to make is to make Compute Normals off by default and Compute<br>
> Scalars on by default so that the output is a bit more consistent.<br>
><br>
> Does anyone think that this is a significant change and shouldn't be done?<br>
><br>
> Thanks,<br>
> Andy<br>
><br>
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<span class="HOEnZb"><font color="#888888"><br>
<br>
<br>
--<br>
| Aashish Chaudhary<br>
| R&D Engineer<br>
| Kitware Inc.<br>
| <a href="http://www.kitware.com" target="_blank">www.kitware.com</a><br>
</font></span></blockquote></div><br>