Hiba,<br><br>This is not exactly what you want, but I have previously obtained reasonable results without specifically calculating the crest-lines. The application I was working on used the crest lines of the skull as landmarks for a deformable registration -- we warped a series of skulls to a single "representative" skull and the crest-lines provided valuable alignment keys.<br>
<br>The way we did this was to first extract the skull surface using the marching cubes algorithm. We specifically chose a threshold to extract out the bone, but you can choose your threshold to extract whatever surface on which your crest lines lie. Given the polygonal surface, the crest lines need to lie on the boundary between triangles. We arbitrarily chose a threshold of 30 degrees between adjacent faces as the level at which we would declare a crest edge.<br>
<br>Unfortunately, I no longer have access to this code, but I think what we did was to walk through the surface data extracting cells, and then for each edge on a cell, did a GetEdgeNeighbors() to find the corresponding cell on the other side of the edge. The test for angle between the faces is then just the dot product of the normals of the two cells.<br>
<br>Again, this is not exactly the crest lines, but seemed to work well enough in our application.<br><br>- Wes<br>
<br><div><span class="gmail_quote">On 2/25/08, <b class="gmail_sendername">Bill Lorensen</b> <<a href="mailto:bill.lorensen@gmail.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">bill.lorensen@gmail.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Wes,<br> <br> You might be able to help this guy.<br> <br> See you tomorrow.<br> <br> Bill<br> <br><br> ---------- Forwarded message ----------<br> From: hiba chelbi <<a href="mailto:chelbi.hibatollah@yahoo.fr" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">chelbi.hibatollah@yahoo.fr</a>><br>
Date: Mon, Feb 25, 2008 at 1:22 PM<br> Subject: [vtkusers] Marching lines algorithm<br> To: <a href="mailto:vtkusers@vtk.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">vtkusers@vtk.org</a><br>
<br> <br> Good evening eveybody.<br> I'm beginner in VTK developpment and i want to know if there is a<br>
function (an implementation of the Marching Lines algorithm) which<br> extracts the crest lines from a 3D image?<br> Thank you<br> <br> <br> <br> ________________________________<br> Ne gardez plus qu'une seule adresse mail ! Copiez vos mails vers Yahoo! Mail<br>
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</blockquote></div><br><br clear="all"><br>-- <br>Wesley D. Turner, Ph.D.<br>
Kitware, Inc.<br>R&D Engineer<br>28 Corporate Drive<br>Clifton Park, NY 12065-8662<br>Phone: 518-371-3971 x120