topic Re: Convert solid to a polyface Mesh (legacy AutoCAD) in AutoCAD Forum

Convert solid to a polyface Mesh (legacy AutoCAD)

nicole — Tue, 08 Dec 2015 19:08:36 GMT

Our customer needs to convert a 3D solid into a 3D polygon mesh, which as I understand is a legacy from older versions. We are able to create meshes from solids using the CONVTOMESH command, but these are 2D planar meshes, not 3D solid mesh. We are able to draw solid 3D polygon mesh (using the PFACE command), but this requires specifying every vertex and face, which is impractical and does not solve our problem. Ideally, we want to convert an existing solid, not create new ones. Less ideal, but still workable, would be an easier method for creating these 3D elements.

Please note that Mesh and Polyface mesh are not the same thing.

They are using SAP 2000 and this requires certain paramaters. Has anyone had to do this and have a workflow they use?

Thank you,

Nicole Morris

KETIV Technologies, Inc.

Re: Convert solid to a polyface Mesh (legacy AutoCAD)

Anonymous — Wed, 09 Dec 2015 18:02:45 GMT

I have a couple notes to add (we're the customer): we’ve tried the AutoMesher add-on, and while converting to what appears to be 3D solid polygon mesh, does not import to SAP2000 (which is our goal).

The example “Pyramid Base.dxf” on this site contains the correct elements we’re trying to recreate. This drawing, and one with elements created using the PFACE command, are the only ones that have worked for me so far.

Re: Convert solid to a polyface Mesh (legacy AutoCAD)

JDMather — Wed, 09 Dec 2015 22:06:38 GMT

Does SAP2000 have a user forum?

Re: Convert solid to a polyface Mesh (legacy AutoCAD)

Anonymous — Wed, 09 Dec 2015 23:54:58 GMT

I am also browsing/posting in SAP2000 forums, but this has ended up being a difficult and time consuming problem for us, so I'm covering all bases. Our missing link in the whole process is being able to convert our solids into polygon meshes in AutoCAD, so I was hoping I might find an answer here for this AutoCAD component.

Re: Convert solid to a polyface Mesh (legacy AutoCAD)

Alfred.NESWADBA — Thu, 10 Dec 2015 08:24:21 GMT

Hi,

can you show a typical drawing/model?

Besides of converting new objects to old ones there is another problem, called accuracy. While 3D-Solids do know curves the old mesh only works segmented. That is no problem as long as you only have flat surfaces building the solid. But when you hace spheres or fillets you will have to go either to a very high mesh density or lower quality. And high mesh density for multiple objects can result in an overload of AutoCAD.

Let's see how your models look like and then decide what can be done.

- alfred -

Re: Convert solid to a polyface Mesh (legacy AutoCAD)

nicole — Thu, 10 Dec 2015 21:36:34 GMT

Hi Alfred,
Thank you for your reply. I believe the customer replied with the sample in the comment below my original.
Thank you,
Nicole

Re: Convert solid to a polyface Mesh (legacy AutoCAD)

Alfred.NESWADBA — Thu, 10 Dec 2015 21:53:29 GMT

Hi,

>> I believe the customer replied with the sample in the comment below my original

I don't see any data, just a link to the page "CSI Knowledge Base" with sample files that are finished. What we would have to dicuss how your drawings are created, what object types exist and what has to be done to get the converted.

BTW: looking to this CSI Knowledge Base a bit more shows >>>this link<<< which describes that importing of a DWG is possible and there objects of type "3DFACE" are listed as allowed. That can be created more easy than a polygon mesh (especially needed the 6x3 mesh).

The way to convert a 3D-Solid to 3D-Faces is quite simple (but don't do that in your original files, as this method is destructive):

Start command _MESHOPTIONS, within the dialog you can select your object, set options (distances and some other stuff to make the result more or less accurate, resulting in meshes with more or less density) and then press OK to get the conversion done.
Next command is _EXPLODE, select the object(s) created with the step before ... and you'll get a lot of 3D-Faces ... done 😉

HTH, - alfred -

Re: Convert solid to a polyface Mesh (legacy AutoCAD)

Anonymous — Thu, 10 Dec 2015 22:51:01 GMT

Let me dig around for a drawing that illustrates what we're trying to do. We may have been approaching this backwards by trying to nail down the general process before applying it to specific products, so I don't have an example handy. In a general sense: we are beginning with an Inventor or AutoCAD solid structure, for example an aluminum hatch with mainly rectangular components (so managing mesh density is less of an issue), and would like to convert these solids into 3D polygon mesh rather than recreate them using the PFACE command.

I'm able to import 3D faces to SAP as shell elements, and this is what I've been doing up to this point. But this only brings in the 2D faces created on the surface of the solids, which, while good for most of the applications I've used SAP for up until now, is not what we're looking for at this point. Our goal is to import elements as solids and the only thing that has worked so far are polygon meshes, such as those in the drawing I linked to previously. I've explored many options on the SAP/CSI side for easily importing solid structures, and have exhasted every option other than converting AutoCAD solids into 3D polygon mesh. I also have some questions into the SAP forums to see if anyone has had success with a different approach, but from what I have found this is the best (or only) option.

Re: Convert solid to a polyface Mesh (legacy AutoCAD)

Alfred.NESWADBA — Thu, 10 Dec 2015 22:59:03 GMT

Hi,

for now I would say you need to develop the conversion to a structure like needed (6x3 polymesh), and depending on how complex your objects are will be the effort.

BTW: I see that IGES is a valid interface, have you tried that? Can be created from both, Inventor as well as AutoCAD.

- alfred -