3D volumes from node co-ordinates

Question

3D volumes from node co-ordinates

duncs (Structural)

(OP)

30 May 04 21:55

hi all,
Im trying to simply work out the surface area and volume of 3-D shapes. they are for transfer chutes between conveyors. Im struggling to make an algorithum that works, concavities are the main hassel.
cheers
duncan

GregLocock (Automotive) · Answer 1 · 2004-05-30 23:56:54

How well defined are your surfaces? Do you just have a point cloud?

Are they basically flat sheets, with intersections?

Cheers

Greg Locock

duncs (Structural) · Answer 2 · 2004-05-31 02:38:17

Hi Greg,
Yes they are basically flat sheets of plate that intersect, each surface is usually defined with 3 or 4 points. aeach point is able to be located with x,y,z co-ordinates.
cheers
duncan

GregLocock (Automotive) · Answer 3 · 2004-05-31 06:32:35

There's a fairly crucial difference there. 3 points define a plane, 4 (generally) don't. If you can live with the 3 point ones then you can generate an equation for each plane(z=ax+by+c, I think), then calculate the line for each horizontal section, and so get a result that way.

On the other hand if you have curvature then things get far more difficult, one way is to use SurfGen.xls to define an easiy spaced grid of points at each Z value

http://www.xlxtrfun.com/XlXtrFun/ReadMeXlXtrFunAndSurfGen.htm

Cheers

Greg Locock

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3D volumes from node co-ordinates