<html><body><div style="color:#000; background-color:#fff; font-family:bookman old style, new york, times, serif;font-size:12pt">hi xavier, <br><br>sum the determinants of the (coords of the vertices of the) triangles.<br>if the surface is closed and oriented, the sum is the volume<br>(or the negative of it) multiplied by 6 (= 3! in 3D).<br><div><br><span></span></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: bookman old style,new york,times,serif; background-color: transparent; font-style: normal;"><span>marco<br></span></div><div><br></div> <div style="font-family: bookman old style, new york, times, serif; font-size: 12pt;"> <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div dir="ltr"> <font face="Arial" size="2"> <hr size="1"> <b><span style="font-weight:bold;">From:</span></b> Xavier Pennec <Xavier.Pennec@inria.fr><br> <b><span style="font-weight: bold;">To:</span></b>
therion@speleo.sk <br> <b><span style="font-weight: bold;">Sent:</span></b> Wednesday, February 27, 2013 1:02 PM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [Therion] the volume of a cave<br> </font> </div> <br>
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Dear Marco,<br>
<br>
Could you expand on how you computed the volume from the dxf file?<br>
I would be very interested to perform that for (no so small) mines!<br>
<br>
Thanks<br>
<br>
Xavier<br>
<br>
<br>
<div class="yiv1019378112moz-cite-prefix">Le 27/02/2013 11:37, Marco Corvi a
écrit :<br>
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<div style="color:#000;background-color:#fff;font-family:bookman old style, new york, times, serif;font-size:12pt;">hi,<br>
<br>
it just happened that i was asked to estimate the volume of a
"cave"<br>
(actually a small mine).<br>
<br>
therion dxf export is a triangulated surface of the cave wall.<br>
if the surface were oriented<br>
it would be extremely easy to compute the volume.<br>
(the surface of a real cave is always orientable: no klein
cave).<br>
<br>
all recent versions of therion produce nice-looking dxf.<br>
i tried 5.3.5 and the volume seemed reasonable.<br>
then i tried 5.3.11 and i got an unreasonable value (there is
also <br>
a commented option for new 3d, and the result was even more
unreasonable).<br>
<br>
so i checked the dxf files.<br>
it seems that none of them is oriented.<br>
is it possible to make therion produce an oriented surface?<br>
thanks.<br>
<br>
marco<br>
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> -------------------------
> Xavier Pennec
> Senior Research Scientist / Directeur de recherche
> Asclepios project-team, INRIA Sophia-Antipolis
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