I have just been producing VRML models from Therion for experiments in 3D printing. My friend who is arranging the printing remarked that the VRML model appears to be closed solids. So perhaps there is a way to convert from VRML to DXF in another application in order to produce an oriented surface model to calculate volume from. Or perhaps an application exists which can calculate the volume directly from a VRML model? Footleg On 27 February 2013 12:27, Marco Corvi <marco_corvi@yahoo.com> wrote:
hi xavier,
sum the determinants of the (coords of the vertices of the) triangles. if the surface is closed and oriented, the sum is the volume (or the negative of it) multiplied by 6 (= 3! in 3D).
marco
________________________________ From: Xavier Pennec <Xavier.Pennec@inria.fr> To: therion@speleo.sk Sent: Wednesday, February 27, 2013 1:02 PM Subject: Re: [Therion] the volume of a cave
Dear Marco,
Could you expand on how you computed the volume from the dxf file? I would be very interested to perform that for (no so small) mines!
Thanks
Xavier
Le 27/02/2013 11:37, Marco Corvi a écrit :
hi,
it just happened that i was asked to estimate the volume of a "cave" (actually a small mine).
therion dxf export is a triangulated surface of the cave wall. if the surface were oriented it would be extremely easy to compute the volume. (the surface of a real cave is always orientable: no klein cave).
all recent versions of therion produce nice-looking dxf. i tried 5.3.5 and the volume seemed reasonable. then i tried 5.3.11 and i got an unreasonable value (there is also a commented option for new 3d, and the result was even more unreasonable).
so i checked the dxf files. it seems that none of them is oriented. is it possible to make therion produce an oriented surface? thanks.
marco
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