# Thread: calculate 3D polyline area

1. ## calculate 3D polyline area

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Hi all,
I'm new here.

Is there a way to calculate a (closed) 3D polyline area ?
Ciao.
Beppe

2. do you mean programatically or just by typing the LIST command ?

3. A 3DPOLYLINE doesn't really define the planes needed in order to calculate an area. So in short, no, you can't. -David

4. Hi hendie and David Bethel,
I know : a 3D polyline doesn't define a plane.
But my question was about how to resolve THAT problem (programatically or not).
Triangulation ?

Ciao.
Beppe

5. Beppe,

I'm afraid you cannot do it. ACAD does not give you enough information.

Example: Draw a non coplaner 3DFACE. Acad does not speciffy whether points 10, 11 & 12 make a face or use 11, 12 & 13. ( These images are fairly poor representation of this. )

The same goes with a 3DPOLY. There is simply no way of knowing which edges match up to make the plane. -David

6. As Beppe mentioned, triangulation is a solution here.

Dono if you have the option, but triangulate the 3dpoly and remove any triangles outside of the polyline.

Then calculate is using eg the Heron formula [3 3D-line lengths] and add them all. See http://astro.temple.edu/~dhill001/tr...anglearea.html and look for Heron.
Proof of the formula: http://www.math.umn.edu/~rejto/1151/1151_heron.pdf.

It depends on how many vertices the polyline got and how they relate to each other. All evenly spread would give best result.

Esri is using same logic: area of accumulated triangles of a tin: http://arcobjectsonline.esri.com/Arc.../bas3DArea.htm

7. I agree with David Bethel: you need more info to calculate the area of a 3D polyline. Here is a sample:

There are a lot of possibilities to construct a surface...

I didn't calculate the areas for these surfaces but probable that are not the same.

8. Hi,

this is an old post but I hope still up-to-date problem:
I am also new to Civil 3D and have similar situation - I was thinking if there is a way to quickly know an area of "footprint" of a 3D polyline? I know I could copy it, flatten and there it is, but if I need information as such for numerous p-lynes I will have a lot of extra work...

Any suggestions?

Mike

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In Autodesk Inventor I would simply create a Boundary Patch and Inventor would tell me the area.
Can you attach your dwg here - perhaps it can now be done with AutoCAD (How complicated is the boundary?)
(I don't use Civil 3D - but I think it can be done there as this has been a pretty common question).

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