Thread Subject: how to calculate volume of a 3D polygon?

does anyone know of a simple way to calculate the volume of a 3D polygon- usually imported from a CAD file?

resolved - found that convhulln gives volume.

On Dec 25, 8:42=A0pm, "Jveer " <jv...@jveer.com> wrote:
> resolved - found that convhulln gives volume.

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Jveer:
Are you sure? Convex hull gives a shape as though you wrapped a
stretchy sheet around your object. So the convex hull of a banana
would be like a thick "D" shape, and the convex hull of a donut/torus
would be like a cylinder. The convex hull of a thick, 3-dimensional
"E" shape would be a rectangular box. This is not the same volume as
the actual volume unless your object is convex.
Regards,
ImageAnalyst

On Dec 25, 7:27=A0pm, "Jveer " <jv...@jveer.com> wrote:
> does anyone know of a simple way to calculate the volume of a 3D polygon-=
 usually imported from a CAD file?

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Do you have a 3D image, or just a list of (x,y,z) vertex coordinates?

oh yeah you are so right. thanks for pointing it out.

do u have any suggestions?

>
> ------------------------------
> Do you have a 3D image, or just a list of (x,y,z) vertex coordinates?

i have the coordinates and the corresponding faces.

On Dec 27, 4:51=A0am, "Jveer " <jv...@jveer.com> wrote:
> > ------------------------------
> > Do you have a 3D image, or just a list of (x,y,z) vertex coordinates?
>
> i have the coordinates and the corresponding faces.

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Jveer:
No I don't. Someone else probably does though. You can try Google.
I just found this:
http://www.niksula.cs.hut.fi/~hkankaan/Homepages/calcvolume.html
If you could somehow convert your vertices and faces to a 3D image
then all you have to do is sum the non-zero coordinates, but poly2mask
only seems to work with 2D polygons.
Good luck. If you find an answer, share it.
ImageAnalyst