<div dir="ltr"><div><div>Hi Stephen,<br><br></div>After thresholding you'll have an unstructured grid again. Can you try extract surface after that again to convert it to a polydata. Then you should be able to generate surface normals. If you don't have gradients available you'll want to compute them before you do the first extract surface filter as well.<br>
<br></div>Regards,<br>Andy<br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Fri, Apr 25, 2014 at 7:40 AM, Stephen Wornom <span dir="ltr"><<a href="mailto:stephen.wornom@inria.fr" target="_blank">stephen.wornom@inria.fr</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I do:<br>
- select extract surface<br>
- select connectivity<br>
- threshhold (to say what surface)<br>
I now have the surface of the wing and nacelle visible.<br>
<br>
To compute the lift and drag, I need to generate surface normals. But this filter is not active.<br>
How do I generate surface normals?<br>
Thanks,<br>
Stephen<span class="HOEnZb"><font color="#888888"><br>
<br>
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