> I tried to export a 3DM from solidThinking but the result is bad,
Yeah, the geometry in the 3DM file appears to be corrupted. I get a similar bad result when trying to open the same file in Rhino as well, here is a screenshot of what it looks like in Rhino:
Also Rhino's "Check" command reports a large number of geometry errors, looks like something about an incorrect vertex structure.
So as far as I can tell solidThinking is not exporting that geometry properly to the 3DM file.
> Is the "STEP" file a better format for convert Nurbs to
> polygonal or is better to use the 3DM file format?
Normally I'd recommend to use 3DM format because that has less calculations that need to be done by MoI on the imported geometry. STEP format tends to only contain the 3D curve parts of trimming curves, making it necessary for MoI to calculate the UV space parts of the trim curves which can be difficult in complex situations.
But in this case it looks like the export from solidThinking to 3DM is buggy so for this particular case it looks like you can't use 3DM.
> If I export an IGES from solidThinking and I open it with MoI
> I can't join the surface, is this a problem of the IGES?
It's probably a tolerance issue, the surfaces are probably not touching close enough for them to be joined in MoI. MoI requires that edge are within 0.005 units of one another in order to join them together to make a shared edge.
I also get a similar result of join failures when importing the file into Rhino and trying to join it in there.
> I attached a movie so you can see the problem (try to scrub
> forward and backward to see the problem).
I couldn't really see what the problem was when running the video at a normal rate. It seems to be very subtle?
That's probably some polygonal artifact that can happen just when rendering polygons that are large in size.
What does the wireframe of your mesh look like in Modo? Does it have some longer tall polygons for the back side piece?
If so, then try breaking those long polygons up into smaller pieces by using the "Divide larger than" setting at export time in MoI. Having smaller polygons can tend to reduce certain kinds of polygonal rendering artifacts.
Remember - polygons are not actually truly smooth objects at all, they are little flat pieces that kind of emulate a smooth surface by doing some tricks. When you have smaller polygons, that can reduce some of the artifacts that can come from not having truly curved surfaces.
See here for some examples of using "Divide larger than" for the MoI export:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2833.5
http://moi3d.com/forum/index.php?webtag=MOI&msg=1084.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=1549.4
http://moi3d.com/forum/index.php?webtag=MOI&msg=804.26
If you produce a more finely diced up mesh, it should probably help to reduce your rendering artifacts.
- Michael
