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

Hi andrew,

> 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.

Usually n-gons work well in Cinema4D, but there are occasional similar problems. As far as I can tell the problems are pretty rare.

If you're looking for a program that handles every kind of n-gon 100% of the time without even any possible exceptions then no I suppose that does not exist.

But also usually people don't seem to run into so many problems with Modo either though.

Usually with either Modo or Cinema4D you can use n-gons most of the time and then for cases where you're running into some problems use Quads & Triangles for those particular cases.


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

Definitely try it out for yourself first - I've heard from people that were using it during its beta release and were not at all impressed with the n-gon output. From what I could tell it looked pretty much like they took triangulated output from the CAD kernel and just attempted to assemble those triangles into n-gons, instead of actually natively generating n-gons as part of the tessellation process.

But it's definitely worth checking out.

- Michael

Moi3d -> C4D works more than great. See attachment.




The only thing is that you cant put a Modo mesh in a C4D Hypernurb. Although I don't think this is something you've planned.



Peace,
Rich_Art. ;-)

Hi Andrew,

I was on the beta of the CAD loader.

The target of the product is CAD users coming from the solidworks world, that need to get their cad data into Modo.
The plugin for example manage instances, meaning you can reduce memory usage a lot in some situation. There is also
a light curve display mode that can help to handle huge model inside Modo.

Now as an exclusive MoI user, it's an other story.

First, I can tell you, nothing can beat MoI ngones output for the moment ... You seems as picky as me about micro details, you will probably loose your hair here with the cad loader.
You can say, from your knobs test here, that ngones dont work well in modo. I respect the pov, but I will continue to use the ngones export. I have render many models at print size, and it's really hard to notice those micro glitches. (In fact I miss them until your post here).

Second, if you come from MoI, you have to deal with .igs or .stp format, and that gives a lot of troubles on the table too compared to a true .3dm loader (or a MoI poly export). Be prepared to have disconnected fillets, holes, inverted or missing surfaces (bad trimming) etc.

I have seen outstanding result with Cad loader, many people are really pleased of the product compared to something like polytrans.
I wasn't that lucky with my models so far.

I think you can request a demo of cad loader now, but I'm affreaid you need at least a 601 licence (601 demo is not out yet).

Hi PaQ, I have Modo 601, and a trial of the CAD loader. It did not generate a mesh with "all quads" at all, but loads of triangles. I could get the areas of triangles smaller by forcing a maximum length to the lines so it would dice things up more, but wanted to show here the results without that. The CAD loader did generate a mesh with good topology for reflections, but the bump mapping problem still remains at the corners. In the end the CAD loader n-gon output is quite similar in complexity to the MOI quads+tris output, but the MOI one is better since the bump mapping works. So MOI quads+tris is the best solution for use with Modo.

Hi andrew, from what I can tell there from your example that the Modo "CAD loader" generated, they really shouldn't be claiming that it actually generates quad - n-gon meshes if that's the result that they actually make.

It really looks to me like they just are taking a triangle mesh that was initially generated by the Parasolid kernel and then just trying to glue those triangles together into n-gons and that makes a kind of chaotic looking n-gon result and can still leave a lot of triangles at the end as well.

- Michael