Geometry problems

 From:  Michael Gibson
656.6 In reply to 656.5 
Hi Jacobo, thanks for the additional testing!

> It's a shame I don't have more complex objects here <...>

Well, that fan/turbine thing is pretty complex, that's a great test.

> - Is there a way to specify the number of layers to be exported in OBJ?

There aren't really "layers" in an OBJ file (or in MoI currently either), but there is a way to group polygons into different objects. That's what happening here, you're getting each different surface exported as an individual object.

That's because the original IGES file has got all the pieces stored as different surfaces - it's not unusual for CAD programs to export data to IGES in this way (as just unconnected surfaces).

So what you want to do to fix it up, is select everything and then run Edit / Join. That will glue together surfaces that have a common edge into a single solid object. Then when you export that one solid, it will result in just one single big object in your .obj file. Maybe I should do this automatically, but on complex objects it might take a couple of minutes or so - that's why I haven't set that up as an automatic process quite yet.

It's also a good idea to join pieces to get the best quality - if you have separate unjoined surfaces they aren't guaranteed to be meshed with an identical structure along their edges. If they are joined into one solid then MoI knows that those edges are shared and will do some extra work to make sure the meshes of each surface are aligned along those common shared edges. Also, joining will ensure that the generated meshes will all have a common normal direction.

> They look fine when you see the polygonal preview in MoI, but when you
> import them into any polygonal software, the object doesn't look right.

Well, it looks like you were loading them into Modo which unfortunately has problems with reading complex N-Gons.

There has been some discussion of it on the Modo forum here:

So I'm afraid that problem has to be solved by them...

Here's what what the n-gon obj file looks like when read into Cinema4D for comparison:

Unfortunately it is somewhat difficult to handle the triangulation of a complex n-gon properly - it is pretty easy to have bugs that cause triangulation to kind of "leak" outside of the polygon boundary like you are seeing in Modo.

- Michael