calculate 3D polyline area

Hi all,

I'm new here.

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

Thanx in advance.

Ciao.

Beppe

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

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

Hi hendie and David Bethel,

thanx for your replies.

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

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

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/trianglearea/trianglearea.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/ArcObjectsOnline/Samples/3D%20Analyst/Surface%20Analysis/Poly%20Surface%20Area%20Via%20Tin/bas3DArea.htm

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.

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

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).

I simply draw a polyline over the 3D Polyline and it will tell me the area in properties. 

Regards,

Marty

There is a formula for an area using points, so disregard the Z and it will give Plan area, if using CIV3D can get 3dfaces and work out the planar area of each 3d face. So the correct response is that there are 2 area solutions. 

Sorry forget where I found this, gives theory for XY points.

(DEFUN C:FACEAREA.LSP ( / MYERROR OLDERROR 
                          SS EN ED P1 P2 P3 P4 AREA3P FAREA)

;;------- SUBROUTINES --------
 
(DEFUN AREA3P (P1 P2 P3 / A B C S)
(SETQ
    A (DISTANCE P1 P2)
    B (DISTANCE P2 P3)
    C (DISTANCE P3 P1)
    S (* 0.5 (+ A B C))
)
(SQRT
    (*
        S
        (- S A)
        (- S B)
        (- S C)
    )
)
)

;;=========== MAIN ROUTINE ===============
 
 (SETQ X 0)
 (SETQ TOTAREA 0.0) 
 (SETQ SS (SSGET "X" '((0 . "3DFACE"))))
(SETQ Y  (SSLENGTH SS))  
        
(IF   (=  SS NIL)
(PROGN 
  (GETSTRING  "\NNO 3D FACES . PRESS ANY KEY WHEN READY ")
  (EXIT)
)
)

(SETQ Y  (SSLENGTH SS))  
(REPEAT Y
        (SETQ EN (SSNAME SS X)
              ED (ENTGET EN)
              P1 (CDR (ASSOC 10 ED))
              P2 (CDR (ASSOC 11 ED))
              P3 (CDR (ASSOC 12 ED))
              P4 (CDR (ASSOC 13 ED))
              )
        (SETQ FAREA (+ (AREA3P P1 P2 P3) (AREA3P P3 P4 P1)))
        (SETQ TOTAREA (+ TOTAREA FAREA))
        (PRINC "\NAREA: ") (PRINC TOTAREA) (PRINC)
           
      (SETQ X (+ X 1))
) ; REPEAT

)  ;DEFUN

(DEFUN C:3FA ()
  (C:FACEAREA)
)

(PRINC "FACEAREA LOADED. TYPE FACEAREA OR 3FA TO RUN.")


(PRINC)

Create a surface from the 3d polyline. And get a surface report. Which will give you the slope surface area and the horizontal area. Or use Surpac to get the best fit area from the 3d polyline