topic How to Calculate the Volume of 3d Object in AutoCAD Forum

How to Calculate the Volume of 3d Object

Anonymous — Thu, 27 Dec 2018 12:44:45 GMT

Hi guys,

I've been trying to figure out a way to calculate the volume of the object in the image attached, it is actually the excavation profile and I want to know the volume of excavation.

Somehow I managed to draw this but now I'm unable to convert this geometry to solid or know it's volume in any other way.

Re: How to Calculate the Volume of 3d Object

Alfred.NESWADBA — Thu, 27 Dec 2018 12:58:35 GMT

Hi,

>> Somehow I managed to draw this but now I'm unable

>> to convert this geometry to solid

From the JPG-file we don't know what you have, what objects these are and so why the current geometry can't be converted to a 3D-solid, uploading the DWG-file would be the better option 😉

>> excavation profile

Are you using plane AutoCAD or Civil 3D?

- alfred -

Re: How to Calculate the Volume of 3d Object

leeminardi — Thu, 27 Dec 2018 15:12:40 GMT

If your 3D model is surfaces and solids you may be able to just add a planar flat surface at the top (ground level) of your model and then use surfsculpt to create a solid model of the void between the bounding objects. Use massprop on the resulting solid to get the volume.

Re: How to Calculate the Volume of 3d Object

JamesMaeding — Thu, 27 Dec 2018 18:18:08 GMT

@leeminardi

interesting, I did not know about that surfsculpt command. I wonder how well it would handle a civil3d surface, exploded to 3d faces, then bounded by a flat bottom surface, and vertical side "skirts" to close the sides.

That kind of closed shape is also needed for 3d printing, and you can use the stlout command if you have a solid.

What I have found so far, is the civil3d surface to solid command, as well as other approaches that do lots of unions on triangle prisms, all fail at about 500k tris.

So I wrote my own surface to stl prog that creates the tris in memory, then writes the stl out. It bypasses the need for stlout, and an autocad solid.

So I wonder how many tris the surfsculpt command handles.

Re: How to Calculate the Volume of 3d Object

Anonymous — Fri, 28 Dec 2018 04:48:22 GMT

I'm Using plain autocad.

The dwg file is attached.

Re: How to Calculate the Volume of 3d Object

Alfred.NESWADBA — Fri, 28 Dec 2018 09:36:23 GMT

Hi,

my steps would be

delete all lines and 3D-polylines (or move them away to see what areas are missing)
command _MESHOPTIONS ... to convert the polymeshes to create mesh objects (from your "Polyface Mesh" objects)
repair the 2 missing areas creating 3D-faces as replacement
command _CONVTOSURFACE (make sure it does not create smoothed surfaces, it should create faceted surfaces)
command _UNION to combine these parts to one surface
command _SURFPATCH with option _CHAIN to create the cap
command _SURFSCULPT to create a 3D-solid from that all
command _MASSPROP to get the volume

- alfred -

Re: How to Calculate the Volume of 3d Object

JamesMaeding — Fri, 28 Dec 2018 16:48:56 GMT

nice post @Alfred.NESWADBA. Definitely 12 worthy!

Re: How to Calculate the Volume of 3d Object

leeminardi — Fri, 28 Dec 2018 17:01:23 GMT

Here's another method.

1. Add the missing surfaces. I used 3dface.

2. Export the file as an igs file.

3. Import the igs file into a blank drawing.

4. Add a flat planar surface at the top of the imported model.

5. Use surfsculpt to create a solid model on a new layer.

6. Use massprop to calculate the volume.