I have a total of 11 very detailed models from a manufacturer, and I need to convert from STEP to .lwo.. No problem, 8 of the 11 has been spotless. The last three models however are having problems with such things as the one depicted below.




Simply put, I'm missing loads of polygons. I've tried different export parameters with no change at all. It differs from model to model what's missing. Some times it's wheels, other times it's handles, like in the screenshot above.

The fun part is that the preview of how it will look with polygons in Moi3D is spotless. Clean and nice.

Have any of you encountered this before? Michael?

Hi Ola - most of the time I've seen stuff kind of like that is when a program does not handle n-gons very well.

What happens if you use Export: Quads & Triangles instead of Export: N-gons, does the render problem go away?

Also double check to make sure you're using LWO and not OBJ format, I don't think OBJ format goes into Lightwave as well.


Is it possible for you to narrow this down to a smaller example file that you could send to me for testing? For example if you could just select only that one messed up face on the handle, then do a Select > Invert and delete everything else, that will make a simple piece that I can examine more easily, as long as it still reproduces the bug.

If you can narrow it down to a smaller problem area like that, please send it to me at moi@moi3d.com so I can take a closer look.


Also, another thing to try - what happens if you delete the vertex normals inside of LightWave, does that seem to remove most of the weirdness or not? If it does then that would help to point to a problem with the vertex normals. Actually support for vertex normals is a pretty new feature in Lightwave.


But probably the first thing to try is if setting Export: Quads & Triangles works better or not.


- Michael

I tried with Tris and Quads. It got a little bit better, but still not perfect. I'll be sending you a part of the model asap.

Hi Ola, thanks for sending me the model through e-mail.

Unfortunately I can't seem to reproduce the problem over here - when I save the model you sent to LWO format and then load that into Modo 203 over here, I get the following result:




Also testing the LWO file going into Cinema4D v10 gives this result:



Unfortunately I do not have LightWave here to test with currently.

But all the polygons seem to be there ok. From your screenshots it looks as though the problem may be some kind of messed up vertex normals and not necessarily missing polygons.



The mesh settings I used were slider all the way to the right (so Angle = 3, the slider controls the Angle numeric parameter on the expanded dialog) and Output: N-gons.
Are you using some particular mesh settings to get your problem result?


What happens if you delete vertex normals in LightWave? There should probably be some kind of mapping entry for them similar to UV coordinates. If you remove them it may recalculate them by averaging them from the polygon normals, which tends to give not as perfectly smooth looking of a result but could also repair any badly mangled ones.


Also are you running any other steps on the model after importing it, like merging vertices or anything other than just a simple import? If so then possibly LightWave is not handling vertex normals properly during that step. That would not be surprising since importing vertex normals is a relatively new feature in LightWave.


Finally, I did recently uncover a multi-threading synchronization bug in the mesher, I'll send you a patch that fixes that just in case that is what you were running into but it was pretty rare.


But try deleting vertex normals, and let me know if you are doing any other editing steps in LW after importing.


- Michael

I believe the problem is with Lightwave since it doesn't read MoI's normals properly.

Missing polys may be that the normals are incorrectly flipped in some cases.


One test would be to download the Cinema4D demo and import your models into that. I found Cinema to import MoI objects perfectly; the model looks exactly the same as it does in MoI...

I've posted this problem at the Newtek site during the v9.6 development cycle and now that CORE is being developed, I plan on once again raising the issue of proper import and use of supplied normal information.

I'd hate for CORE to be released and still not be able to use my MoI objects as easily as I can with Cinema 4D!

-Will