I am doing the same UV mapping as stated in my first post, a cylindrical mapping around the knob in the direction of the lines shown. This is a one click operation in Modo using the "UV Projection Tool" and gives perfect results for tri + quad meshes from MOI, including the bump map for the brushed aluminium stock modo material, which I manually change the size of to 50 um bump depth - the whole knob is 14 mm in diameter. I've attached a closeup of the UV map of the area in question:



I was told that everyone was using n-gon export to Modo without issues, so I thought I would give them another and document it all in this thread for everyone to comment on. N-gon output still don't work properly with Modo for me no matter what I do. Even with a basic reflective surface only and no bump maps I still get incorrect lines rendering where non coplanar n-gons don't line up very well. If there are any other MOI + Modo users reading this thread can you please download the .3dm of the knob and give it a go with a basic reflective surface and zoom in on the same vertical fillet and let me know how you go? I always end up getting stuff like:



Michael, is it possible to split up non co-planar > 4-gons into a bunch of 4-gons? This may help for programs like Modo that can't seem to handle non co-planar > 4-gons very well. Any planar > 4-gons could remain to keep the poly count down for easier selection and UV mapping without going to the full mess that is tri + quads.

Mmm I'm looking a little more closely to the MoI tesselation, and I'm not really sure now if MoI is not doing something weird too on this particular model.
I have a 'deja-vu' feeling here, but I dont remember if it's 'normal' or not.

Here's a closup of the knob in MoI,



It's really strange that ngones and quad output dont give the same shading result in MoI either.

Hi Andrew,

There is definitively something wrong with the .lwo, and the way modo internally trianglulate ngones.
I think this is something that can be resolved, but from the luxology side.

For this knob example, you can try to export it in .obj, using ngones.
You will probably get some inverted normal in modo, just double hit the 'F' key to fix it ... but at least will not have this ngones shading problem, as the inernal triangulation will be fine.

At least I have concrete example now I can show in the modo bug report.

PaQ, thanks for letting me know you are having similar problems with rendering in Modo. We overlapped posts, thanks for already taking the initiative to go ahead and download the file and try it out with a reflective surface - really appreciated! Sounds like I need to join up the Modo bug reporting thingy too, and also report the issue with bump maps not working as expected with these n-gon type topologies as well.

I get identical results using either .lwo or .obj for export. Here is the same thing with a .obj file:

Hi Andrew,

Well you are welcome, I'm quite concern but the problem too ... and I'm wondering how do I miss that since 2 years or so :P

The bump is probably a side effect of this triangulation problem, not sure.
But a wrong (or not optimal) ngone tesselation produce UV stretching too ...

I've tried to isolate the problem as much as I can, like Michael teach me :)



So a question for Michael, because there is something I dont really understand :

In the .lwo created by MoI, is this internal triangulation of ngone write somewhere ? Why is this information lost, or no well translated from one software to an other ?

Well actually I have better result here, (using 601, using obj)



But ... it's not perfect everywhere, there are still some area when ngone create micro triangle that break the shading.



... better wait Michael now to have more advanced advice.

Between modo creating funky ngones, and MoI introducing strange glitches when using triangle export format, I never saw so many
problem for a so simple object :P

I get a perfect render from Modo 501 with this 3dm file. Export was ngons, 6 degree angle.




I also get a perfect render from 601 after changing the LWO option to Lightwave 10 to avoid the vertex nornmal issue.

Hi PaQ,

> So a question for Michael, because there is something I dont
> really understand :
>
> In the .lwo created by MoI, is this internal triangulation of ngone write
> somewhere ? Why is this information lost, or no well translated from one
> software to an other ?

Usually formats that support n-gons only store the n-gon itself and don't have any way to additionally store a triangulation of the n-gon at the same time.

It's up to the receiving application to do the triangulation, and it's not a particularly easy task, there are quite a few ways that it can go wrong.

- Michael

Hi andrew,

> Michael, is it possible to split up non co-planar > 4-gons into
> a bunch of 4-gons?

There's really no straightforward way to do this by only connecting together points of the n-gon.

In order to "quadify" things it tends to require more vertices to be created, and then that's the whole problem of trying to automatically arrange vertices for quads where different pieces are colliding into one another - a difficult problem to solve.

- Michael

Hi PaQ,

> It's really strange that ngones and quad output dont give the same
> shading result in MoI either.

They generate a different result if the "Centroid Triangulation" style is on (which it is by default). That's settable under moi.ini under [Mesh Export]:

[Mesh Export]
CentroidTriangulation=y

When that's set, then for "Quads & Triangles" output, when possible an additional point is added to the centroid of the n-gon and triangles are formed by connecting to that, making a kind of radial triangulation.

When you are doing "Output: N-gons", the display mesh that MoI generates for the n-gons does not do that centroid style triangulation.

So you'll only get an exactly matching display in MoI if centroid triangulation is turned off.

- Michael

Hi SteveMacc, I don't see an "n-gon" output export option for 3ds files. Is this something new in the V3 beta? I'm running MOI V2.5 beta on mac, here is the dialogue I see:

Hi andrew - 3ds files can only contain triangles.

Are you referring to Steve's message here: ?
http://moi3d.com/forum/index.php?webtag=MOI&msg=4978.21

It looks like he wrote there that he was using your 3DM file (not 3ds?), and using LWO format.

I wonder if your problem has something to do with using both reflection and uv mapping together in your rendering though.

- Michael

Yes you're right Michael, I misread 3dm as 3ds, thanks for spotting that. I've used SteveMacc's suggested 6 degrees with n-gon export of and lwo with Lightwave 10 options and rendered in Modo 601, but there are still problems, I get the same holes in the reflectance either scaling to meters (which is the correct option to keep the materials all the right size), or not scaling to meters:



There seems to be two problems with Modo's rendering of n-gons from MOI

1) the reflection not being correct for non co-planar n-gons
2) the UV mapping of bump map having trouble with non co-planer n-gons

The only solution to get problem free renders is to using quad + tris for the export to Modo, adjusting the divide larger than and avoid smaller than settings to get a good division of the geometry. In the end the number of polys is around the same as for one of these more detailed n-gon exports, I was only trying to get n-gons working since I was told that they should work great with Modo, I'm happy to not use them and get on with it. Here are the correct renders of the knob done with quads+tris:

Hi Michael,

Thanks to remind me the Centroid Triangulation option, I completely forgot that one, sorry.
Turning off the Centroid Triangulation also resolve the weird triangulation effect on fillets from the previous post.

Hi andrew - I think that possibly Steve's one worked ok because he used a different way to set up the reflectivity - probably something like just a material property and not reflectivity coming from a texture map.

I guess that N-gons in Modo do not work ok for the particular combination of render features that you are using there. I don't really know what more I can tell about that, you would probably need to contact Luxology to get more specific information on it and to see if it's something that can be fixed up over there or not.

I'm not really sure what I would do from the MoI side to improve that, other than some completely different "all quad" meshing mechanism which is of course a tremendous amount of work and not something like just a tune-up or bug fix...

You could probably verify that it's a Modo-specific problem by drawing the same n-gons just directly inside of Modo, they should likely exhibit the same problem whether you drew them in Modo or whether you imported them from MoI.

But for now anyway if your issues are solved by using Quads & Triangles instead of N-gons then that's the way to go.

- Michael

The error in Modo's reflective rendering has nothing to do with UV mapping issues as far as I can tell. For the purely reflective images I've posted I have manually set the material to be a single BRDF layer with diffuse=0 specular=0 or 20 (doesn't matter) roughness=0 reflection=100 and blurry reflections off, so UV mapping shouldn't come into it.

I think Steve just didn't zoom into the appropriate part of the render, and also has a "busy" background which obscures the issues as well.

Hi Michael - my other choice for a 3D package was Cinema4D, but from this thread: http://moi3d.com/forum/lmessages.php?webtag=MOI&msg=3869.65 it looks like n-gon output doesn't work either. Do you know of any 3D package that can actually render non co-planer n-gons correctly? If so you can please let me know the names and I'll download the demos and give them a go. I am guessing none of them will do a proper job on even basic geometry with n-gons like the knob I've done, let alone something actually complicated.

I noticed that Modo has now (as of 601) got a CAD Importer package that supports IGES and other nurbs type input formats. I'll also try to give that a go and see if it can generate better geometry than MOI, and if so I'll export to IGES and import using the Modo converter. Shame though since your product is half the price of the converter alone. I'd rather give you the extra money for a better n-gon exporter than to Siemens PLM Software:

A quote from the page: http://www.luxology.com/store/CAD_Loaders_for_modo/index.aspx

“The CAD Loaders for modo are an awesome addition to my workflow. The quad-based import option is an outstanding improvement. Eliminating triangles from my imported geometry results in an asset that is easier to work with and occupies a smaller memory footprint. In addition, the wide variety of CAD formats is a huge plus.”
– Paul McCrorey