I may be wrong but I think that setting "Avoid smaller than" to something like 0.001 should avoid some of the tiny edges on the output mesh, making it somewhat cleaner.

Hi FlashFire,

> I wanted to point out that sometimes poly artifacts can show
> up even when C4D is used to render a moi model imported
> with normals.

That shouldn't be the case - do you have an example model you can post? Please post the actual model file though and not just a screenshot.

Also your last screenshots did not show what the rendering looked like in Cinema4D - with the proper vertex normals coming over, models such as you show there should not have any artifacts in them at all, they will look the same as the original NURBS object despite that kind of topology.


> Many points have to be manually welded/cleaned up.

This may mean that you have not prepared the model properly - make sure to join surfaces that are sitting next to one another so they will get a watertight mesh created for them.

If you have surfaces that are not joined to one another but are just sitting next to one another as independent objects, that will make them get meshed independently and they can have get separate vertex structures created for them in that case.

Also you may just need to create a bit higher density mesh to get a smoother looking result.

Don't forget that polygon models are not actually smooth things, they're made up of little facets and the smoothing is a kind of visual trick that's done by using vertex normals. If you have a small number of facets, that can stop the illusion of smoothness from working very well.


> Look at the polys to the left of the words output: and display:

Those should not have any problems in the actual render in Cinema4D with proper vertex normals on them.

Have you possibly turned off the import of vertex normals into Cinema4D?

Also I would recommend using n-gons - Cinema4D has very good support for n-gons and while it is possible for there to be n-gon triangulation problems in Cinema4D, it is quite rare, so I would recommend using n-gon output for regular use, and only switch to Quads & Triangles output for some special purpose when you have actually identified a problem rather than just defaulting to that.


It would really help though if you could post a model that you're having problems with though instead of just screenshots.

I think some of your prior polygon modeling experience may be working against you - if you built a regular polygon model with slivery polygons like that, that could indeed cause artifacts because it's hard for the smoother to make good vertex normals cooked up from scratch on polygons like that. So you seem to be just assuming you're going to have problems because of that topology. (it sure seems like you're just assuming that anyway since you did not show any rendering result). But when you have vertex normals coming in from the original NURBS surface, that is a completely different things and won't have the same kind of artifacts.

It's important though to make sure the vertex normals are being preserved though, that's the key thing that makes the render of topology like that look totally smooth and keep the same appearance as the original NURBS model.

Another general problem you may be running into kind of related to your past sub-d modeling experience is that you may be producing too low polygon of a result out of MoI if you're seeing artifacts. Remember that you're not going to be relying on sub-d smoothing to be applied to smooth out the model further, so you should not try to make as rough of an initial cage as you would if you were doing a sub-d model.

If you make a low poly model you can get various kinds of artifacts that are just part of being low poly. The solution to that is to increase polygon density.

- Michael

So anyway if you post the model I'm quite confident that I can help you get it rendered in Cinema4D without any trace of artifacts in the rendering whatsoever....

This has come up before where someone who was used to poly modeling just assumed that they were going to get shading glitches in Cinema4D when that was not the case, here is the thread:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3533.1

And here was the rendered result of that:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3533.11

The only trick applied to make it look totally smooth and perfect in Cinema4D was to ensure it got refined with enough polygons to avoid low poly artifacts.

So for example you mentioned previously that you are using "avoid smaller than" in your mesh settings - don't do that, as that avoids refining in areas and will produce a lower polygon result.

If you want a better quality rendering without low poly artifacts, you need to produce more polygons.

If you produce a low polygon output model, it will have low polygon related artifacts in it when rendered, that's pretty straightforward.

- Michael

Thanks all for the feedback

I have no problem getting a model to render ok. I'll just not be using N-Gon output to do so anymore ;)

My question is, why can't a function to automatically weld points within a distance such as the ones circled in
red be added to the meshing options dialog box? I too thought that was what avoid smaller was for, but to no avail.

Well, what you said a couple of messages above was:

> I wanted to point out that sometimes poly artifacts can show
> up even when C4D is used to render a moi model imported
> with normals.

If you can post the model, I'll show you how to render it in C4D without any visible artifacts at all.

Most likely the artifacts you were referring to were related to low polygon count and not due to the topology stuff that you are posting screenshots of.

But it's difficult for me to verify this since I cannot test a screenshot. If you were to post the model that would give me something I could test and that would help me give you better feedback.


> I too thought that was what avoid smaller was for, but to no avail.

Avoid smaller than doesn't cause welding to happen as a post-process - what it does is make polygons that are smaller than that threshold distance use a rougher angle than the regular angle setting during the refinement stage of the meshing.

It's for producing lower detail on small sized portions of the model. Say for example you have a model that has a lot of little tiny rounded buttons on it, and you don't want very many polygons on those. You can make those small areas get a lower poly count by using "Avoid smaller than".

Here's an example of a small area that is getting quite a few polygons - this happens because the regular angle parameter is scale independent - it works just off of curvature and not size, so a large size rounded thing and a small sized rounded thing that have the same roundness get the same poly density with just the angle parameter:



That little rounded thing is about 0.5 units across, and so if you wanted that small area to get a lower level of detail you can enter in "Avoid smaller than = 0.5", and that will produce this instead:




It does not force welding to happen as you were thinking...


> My question is, why can't a function to automatically weld points
> within a distance such as the ones circled in

It's somewhat hard to do this and also maintain the accuracy of the mesh adhering to the original NURBS object at the same time.

If points that are too far apart get welded to one another, it produces a kind of divot or bump cutting into the mesh.

The other thing is that kind of welding would not really serve any purpose for rendering, if you post a rendering of the unwelded result that you show there side by side by a welded one, they would be indistinguishable in the actual rendering so long as the imported vertex normals are used.


Once again though, it would really help if you would post the model file of the stuff you are showing instead of only a screenshot.


- Michael

Also I still don't understand why you refuse to use n-gon output.

Cinema4D has great support for n-gons, why do you not want to take advantage of it?

N-gons would make for a much cleaner wireframe in those areas that you are circling, those will just be a couple of additional little points around the n-gon perimeter instead of being a bunch of triangles in the wireframe.

- Michael

I have had to manually fix polys even in C4D using ngons. Some were flipped on some models, and sometimes edges overlaped.
This of course won't happen with a mix of quads and tri output from moi.

> I have had to manually fix polys even in C4D using ngons.

How many times has that happened?

Why not use n-gons as your default and only use quads & triangles output in the few particular cases that you need it where C4D's n-gon triangulator has a problem?

- Michael

Hi, everybody – Sorry to hijack this thread for a quick question...

I'm a new user, and I'm looking for a rendering application to use with MoI. Michael - you mentioned Cinema4d for N-gon support. And I also read, that there's Modo, which complys to N-gons and preserving normals, when imported from MoI. Is there anything else you could recommend?

Regards,
Sebastian

Hi Sebastian, Cinema4D and Modo seem to be pretty popular right now.

If you want something less expensive, Carrara could be a good fit:
http://www.daz3d.com/i/software/carrara8?_m=d

A few other discussion threads on this:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3136.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=3652.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=3401.1


But there are quite a bunch of various renderers out there and many have a focus in particular areas, like some are focused on production for rendering movie stills, some have a bunch of stuff in them for making outdoor scenery, some are more focused on more hobbyist type use, some do both rendering and animation in the same package and some only do rendering, etc... etc...

So it can depend on what in particular you want to do with it.

- Michael

Hi Sebastian, also a fairly new renderer that several people here have tried out and liked is Simlab Composer: http://www.simlab-soft.com/3d-products/simlab-composer-main.aspx , their rendering-only edition is $149.

For exporting to Simlab you may need to use OBJ format with "Quads & Triangles" output rather than n-gons though. But n-gons are not required to get a good rendering, they're more of something that are nice to have just to keep the wireframe nice and tidy. Support for the vertex normals is much more important for getting a good looking final rendering.

- Michael

Hey, Michael

thank you very much for all those suggestions and reads – I'll have a look into those.

Regards,
Sebastian

I remember a discussion on Modo forum, where someone qualify MoI mesher been "bad" because the topology was not sub-d friendly :)

Btw I dont know for C4D, by when you start messing with MoI topology in Modo (merging, flipping poly etc), you just introduce all kind of shading artefact because the vertex normal is not right anymore.
Otherwise, the rendering is just perfect with MoI ngones, I dont remember any glitches since one year or so ...

Hi PaQ,

> I remember a discussion on Modo forum, where
> someone qualify MoI mesher been "bad" because
> the topology was not sub-d friendly :)

Yes, some people seem to expect that it should magically create the same topology as a highly experienced sub-d modeler would do by hand... And no doubt, that certainly would be cool if it could optionally do that (optionally because as I mentioned previously sub-d friendly topology and sparse wireframe n-gon topology are actually different things).

Unfortunately that level of expectation is what I'd call "pretty highly unreasonable" though. It's very difficult for software to replicate things that require a kind of case-by-case human judgment to them.

There are some interesting new auto-topology tools in 3D-coat recently but that overall technique is more for a kind of all smooth blobby sculpted shape and not really for CAD solids so much, particularly with a mix of large and small features.


> Btw I dont know for C4D, by when you start messing with
> MoI topology in Modo (merging, flipping poly etc), you just
> introduce all kind of shading artefact because the vertex normal
> is not right anymore.

I'm not 100% sure but I think C4D will automatically delete the vertex normals if you do some editing operation that makes them invalid.

It would be good for Modo to do the same thing as well, just automatically delete the vertex normals if you do something that modifies the shape of the mesh like pulling some individual vertices around.

The vertex normals information is something that should be tied to the current particular shape of the mesh. If the shape changes it just does not make sense to apply the same normals from its previous shape to its shading, yet that is what happens in Modo currently I guess.

But it's also good for the vertex normals to be kept and transformed with operations where it is possible to do so, like if you transform the whole mesh (like by rotating or scaling it so the overall shape of it stays the same), or also flipping a chunk of mesh does not need to invalidate the normals it can just flip them as well. It's not really very complicated stuff, so it's kind of surprising and frustrating that this is often not handled well.

- Michael

**It's not really very complicated stuff, so it's kind of surprising and frustrating that this is often not handled well.**

Yes, thats true. I own Cheetah3d (MAC only, since I run MoI in Parralels) and was asking the developer over at the forums, what's happening. He told me, that vertex normals are recalculated automatically on import. So there's no chance I use this as a renderer without having to "polyflipweld" my ass off. :-)

Regards,
Sebastian

Hi Sebastian - that's unfortunate re: Cheetah3d not using the vertex normals from the file and instead calculating new ones, it's discarding some important data there. With CAD data, it's never going to be able to calculate the same normals since all it has to work with are a bunch of facets and not the original NURBS surfaces.

One thing that can help somewhat with that is to try and make a more finely diced up export from MoI, using the "Divide larger than" option to break polygons down to a more uniform size. But even then you're still going to see various imperfections in the shading. It's soooooooo very much better to have the true vertex normals - getting the true vertex normals over results in a super smooth and perfect looking render without any messing around at all.

Automatically calculated normals don't work very well with things like a large polygon face right adjacent to a bunch of small polygons for a rounded edge, it's too easy for the little poly on the rounded edge to overly influence the shading on the large polygon with stuff like that, and that kind of large flat face next to a rounded edge is a common kind of structure with CAD models. More organic sub-d models tend to work ok with automatically calculated normals because they're typically constructed out of all the same general sized polygons that kind of gradually bend around.

So some rendering programs that have become very focused just on dealing with sub-d models may not really know how to deal with CAD data that has a different structure than organic sub-d type models. But that's becoming fairly rare now, most renderers out there are able to import vertex normals these days.

- Michael

Hi Michael,

I've tried various settings with the MoI exporter to use the mesh with cheetah3d - nothing worked without glitches. The only semi-acceptable solution is turning off "weld" so you get phong breaks, where the faces meet, but the surface of single faces are completely smooth.

I think I don't get around buying modo for this. Theres actually no other software for MAC, that lets you edit UV, imports normals from CAD and has a great renderer...and won't make me beg for a credit at my local bank (like autodesk would)

;-)

Hi Sebastian, yes the "edit uv" part kind of narrows things down somewhat.

Although another possibility might be to use a dedicated UV editing utility for that part, like UVMapper http://uvmapper.com/downloads.html there seems to be a "classic" version there for the Mac which looks like it is free, so that may be worth checking out to see if it can do the uv editing that you want.

Then that would enable you to use something like Simlab Composer for rendering which also has a Mac version I believe.

But it sounds like Modo or Cinema4D would have all of what you are looking for in just one single package so that could definitely be useful.

- Michael

Ahh Ha! I found a quicker workflow to importing a model into 3DS Max without normals. It's v6 ;)
This model "Thank you to Steve, it's and excellent test" was imported as an obj using moi's output to ngons.

NGons came in great, but I knew I'd have to add smoothing groups. No biggy usually auto smooth at 45 degrees is great.
I added an edit poly, welded points as far as possible without damaging the model.
Then selected all polys and clicked the retriangulate button.
All that was left to do was less then 5 mins worth of edit triangulation, to turn some edges to eliminate sliver type polys.
Finally selected all polys and added auto smooth 45 degree. Any more bad smoothing errors will show up as to many smoothing
groups. This time however it created just 2 groups using auto. One flat grp, for the bottom, and the rest of the model for the other.



The moral of this story for me:
I think what I've learned from this thread is that you can't get away with not tweaking your model in some form or another
in your final rendering software. That is, it's very rare not to. ;) For me same has gone for C4D even 11.x. But being a well
seasoned veteran of polys, it's probably something I look at more closely then most CAD users. Although, you can see by my
3DS max version it hasn't been my full time career since at least 2005. ;)

To Steve's defense:
By the way yes slicing can take time to workout in Moi but can be a great way to force a sort of poly structure.
Although I can't get it anywhere near as clean as the radial sliced model shown earlier in this thread.

My Sliced model in Moi
Not meant to be for meshsmoothing just as a way to tidy things and force better smoothing groups in polygonal renders:


In retrospect, I'd say well over 75 percent of polygonal models I had created years ago with strictly 3DS Max required some
poly tweak or another. In particular when you had to use a boolean in that software. Booleans in polygonal software require hefty
point weld edge turn etc...

Hope I'm not hijacking

Hi FlashFire,

> The moral of this story for me:
> I think what I've learned from this thread is that you can't get
> away with not tweaking your model in some form or another
> in your final rendering software. That is, it's very rare not to. ;)
> For me same has gone for C4D even 11.x.

I'm kind of confused about how you ended up with this moral.

What is it that you are trying to use the model for in your final rendering software that forces you to tweak the model?

If you are actually rendering it (which is quite frequently the thing that many people do when importing models into rendering programs), then no there should not be any kind of tweaking required at all, just import the model, then render it and that's it....

Just make sure that you are importing vertex normals, that's the key thing that makes a great looking rendering _without any additional tweaking_ !!

Here is a simple example with that same block model.

You load the model into MoI, it looks like this:



You save from MoI to OBJ format, the polygons generated look like this:



You then import the OBJ into Cinema4D, and without needing to do anything special, you just render it and it looks like this:



So note there that the amount of extra tweaking is none! For rendering, that should be the normal thing, it is not required to do any additional poly tweaking if you want to produce nice looking renderings from your model.

If you want to reduce jaggies in silhouettes or something like that, then you do that by tweaking the export settings from MoI, which will usually involve just moving the slider over to the right some more to generate a larger number of polygons.


> For me same has gone for C4D even 11.x.

Do you have any example model that you can post that you were having a problem with rendering in Cinema4D ? If you post it, I can help show you how to get it rendered nicely in Cinema4D without needing to actually mess around with tweaking any polygons in C4D.

- Michael