On Tue, Nov 30, 2010 at 9:25 AM, David Doria <span dir="ltr"><<a href="mailto:daviddoria@gmail.com">daviddoria@gmail.com</a>></span> wrote:<div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="im">
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</div>So it considers a point on the boundary to be "outside" no matter the<br>
tolerance? Doesn't that seem silly? Often you may know the coordinates<br>
of the grid points and want to get the cell id they are associated<br>
with. This method should work for all such points, but it seems to<br>
work only on points that aren't on the boundary faces of the<br>
structured grid?<br></blockquote><div><br></div><div>Hmm... I looked at the FindCell implementation in vtkImageData, and it ignores</div><div>the tolerance completely. This is not good. As you said, boundary points</div>
<div>should be considered to be inside the cell unless the tolerance is strictly set</div><div>to zero (and even then, it should be an even 50/50 chance that the boundary</div><div>points are considered to be inside).</div>
<div><br></div><div>In fact this is precisely the sort of boundary issue that tolerances are for:</div><div>to ensure that points on the boundary are not mistakenly marked as "outside"</div><div>due to roundoff error.</div>
<div><br></div><div>I'm not saying that it huge tolerances are reasonable (they aren't, tolerances</div><div>should be small by definition) but tolerances should not be ignored completely...</div><div><br></div><div>
David</div></div>