Hi Pilou,

For this type of construction, no. Lineweb is loft with only edges created, rather than edges/faces. So the same limitations.

If I was to go the route of creating the edges for facets in MOI, then I would create the model, extract the needed edges, then convert them to polylines(Using the rebuild to polyline script), then have those polylines imported into a poly modeller, then create Gordon/Coons surfaces, or even use (maybe) sweep functions in the poly modeller.

- Steve

Well for me editing poly structure of an imported moi model inside C4D was far faster then the slice up
method shown in the above post. Unsure if importing as an .lwo into C4D works better then riptide plugin as .obj.

Model I tested was a rail swept model similar to the one above.

Hi Flashfire, if you have time could you post some screenshots of your process?

Marc

I just looked for edges which would cause the test model to improperly hypernurb and dissolved them in C4D. Then
tested hypernurbs and it looked great. Unfortunately I find you almost have to do some cleanup like this if you plan on using
a mesh smooth or hypernurb method in 3D poly software.

Before doing this in C4D I used optimize to weld points of the original model.

Hi Flashfire,

> Unsure if importing as an .lwo into C4D works better then riptide plugin as .obj.

If you're going to be editing it, it shouldn't make any difference one way or the other.

But if you're going to be rendering the model directly you should use .obj format for that since that will preserve vertex normal information which helps the shading look the same as the original NURBS model, since the normals used for shading actually come directly from the original NURBS surface in that case.

I don't think that C4D knows how to read the vertex normals out of an .lwo file (until the last few years it was not really something that was found in LWO files), so it will instead cook up the vertex normals for smooth shading by averaging the normals of surrounding faces which is not really as nice as using the normals from the original NURBS model.

If you edit the model at a vertex or face level, it will invalidate any existing vertex normals and cook up new ones though, so that's why if you are editing it, it won't make any difference.

- Michael

There's also TopoGun (http://www.topogun.com/) which is a retopologizing program which is dedicated to this task of generating a quad only sub-d friendly topology.

Also 3D-Coat (http://www.3d-coat.com/) has a variety of retopo tools in it.

- Michael

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Quote FlashFire
>>Well for me editing poly structure of an imported moi model inside C4D was far faster then the slice up method shown in the above post.<<
-------------

The examples in this thread are extremely simple. The surfaces have very little difference in length and the Mesher in MOI will actually give you a result that can be easily edited in a poly modeller.

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Quote FlashFire
>>Model I tested was a rail swept model similar to the one above.<<
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If that surface you show in your last post was your "Test", well, that is even more of a simple example than the ones show previously, as your example appears to be a single surface.

For a simple example, showing the kind of problem with quad mesh creation, lets look at this simple block with 2 curved surfaces with fillets.



Now that is easy to create in MOI and not much more difficult to create in a poly modeller. But if you output a mesh directly from MOI from the model as it is, then the mesh would not be so easy to edit into quads.

My point was nothing will be perfectly setup out of the box, output just has to be edited if you plan on using a mesh smooth or hypernurb function. Normally I use riptide, but just thought I'd try .lwo. It's good for like Mike said, when you need to
edit anyway. Or a quick and dirty way.

But I wanna have a go at editing that button model using C4D to make a clean model for hypernurbs... ;)

Hi Steve,

> Now that is easy to create in MOI and not much more difficult
> to create in a poly modeller. But if you output a mesh directly
> from MOI from the model as it is, then the mesh would not be
> so easy to edit into quads.

Yup, but that's also a good example of a model where there would not be any particular purpose (that I can tell anyway, let me know if there is one) for why you would need that model to be all quads.

It's got all rounded parts in it already, it's not like a rough mesh that you're trying to smooth out by applying sub-d smoothing on to it.

It does seem to be fairly common for people to want to get things as all quads even if there is not any particular benefit for their particular case, I guess because they've heard that it's good to have all quads if you are going to be doing sub-d modeling.

But when you create a model like you show there, it's all finished up, it's not like you need to apply sub-d on to it additionally. In cases like that there is no need to have all quads, you just export that model from MoI and take it into your rendering program and render it.

In general the output from MoI is oriented towards that kind of use where you're going to take the model into your rendering program and render it. Taking it in as a sub-d control cage and then applying smoothing to it is kind of a weird thing to do to CAD models since that sub-d smoothing actually kind of melts and changes the shape.

If you already have the thing in the shape you want, then you're all done with the model... Running sub-d smoothing on something that is finished does not just automatically "improve" it, it can mutate it and even potentially introduce ripples and bumps in it if the topology is not organized in a sub-d friendly layout.

By the way these comments are not necessarily directed at you in particular, these are just some things that come up fairly often with a variety of people, particularly people who come from a sub-d background where they're so accustomed to only working with quads.

- Michael

Hi Chris,

> But I wanna have a go at editing that button model
> using C4D to make a clean model for hypernurbs... ;)

But why??? What would be the point of that - the model is all finished up and has all rounded edges already...

What would there be gained by applying hypernurbs / sub-d smoothing to a model that is already in its proper finished shape?

You will actually lose some of the model accuracy by doing an extra sub-d smoothing on top of it, for example things that used to have vertices arranged in exactly a circular arc shape will get kind of melted and not have everything exactly on a circle anymore, stuff like that. If you have things diced into small enough pieces the melting effect will be reduced and more localized but what would the point be?

- Michael

Hi Michael,

>>Yup, but that's also a good example of a model where there would not be any particular purpose (that I can tell anyway, let me know if there is one) for why you would need that model to be all quads.<<

Just an example of a model with different surface sizes/flows that will show how the mesher works on those surfaces in MOI.
For me personally, I do not consider a need for quads, 99% of my models(for personal use/projects) are hard surface. I can easily have a model in n-gons and it will do for me and the renderers I use.

 

- Steve

Hi Steve, actually n-gons can give you a more efficient and cleaner structure in certain ways as well. Like in your example model there all the planar surfaces (top and bottom caps and 4 vertical side walls) will just have 1 single n-gon for those spots. Having all quads would require those spots to be tiled into a bunch of little small quad fragments instead of just 1 face.

Having a smaller number of elements like that can be nice in several ways - poly count can be lower, wireframe can be sparser, things like selecting faces for assigning properties can be easier, ... The main thing that doesn't fit is applying sub-d smoothing. But if your model is finished, there is no need to apply sub-d smoothing to it anyway.

On the other hand if you do want to do sub-d smoothing in the general case I recommend using a poly modeler to create the mesh for that since they have tools that are specifically focused on making topology for that particular purpose. In certain special cases you could use MoI for that, like if you use the dicing technique you showed earlier or if you have just a single untrimmed surface that can go into quads more easily but in general MoI's solid modeling toolset and n-gon mesh generation just is not the right tool for the job of producing sub-d quad meshes, it's focused on generating render-ready efficient n-gon meshes instead which is a totally different kind of mesh structure.

- Michael

Actually I was lowering the poly res of the output model to be able to up the res using hypernurbs.
Just as a test of how well you could make a low res cage of a model using moi.
No I wouldn't want to add resolution to an already rezed model. ;)

Just was a fun test that caught my eye.

Here is the block moi file imported into C4D as a lower res poly model shown in the 1st image.
The model was then cleaned up manually using slide points and optimization/welding points.
Then mirrored the 1 quarter part to make a whole.



Now in the second image the final model is hypernurbed by 1 iteration.
It was a quick edit, so didn't pay that much attention to making quads
Detail is still retained. Not sure why you would think it would melt it.....All in how you lay out the polys.



Admittedly for a complex model you might pull your hair out ;)

Hi Chris,

> Not sure why you would think it would melt it.....

Well, try hypernurbing a cube and you will see it greatly change shape, melting down to a kind of ovoid shape similar to a sphere.

Just in general the action of applying sub-d smoothing changes the shape of things like that.

You can reduce the amount of change by having more polygons that don't have very sharp angles between any pair of them. But the shape change is still present, so like I mentioned previously things like vertices that used to be perfectly arranged in a circular shape will not have the smoothed results exactly arranged in a circle anymore.

It's also quite easy for ripples or lumps to be formed in the sub-d result in response to some kinds of topologies. See this video for some examples of that kind of stuff:
http://guerrillacg.org/home/3d-polygon-modeling/subdivision-topology-artifacts

So it's quite possible during this conversion process that some kinds of ripples and bumps will get introduced into what was previously a very exact and smooth NURBS-generated model.

Applying sub-d smoothing does not just automatically "improve" a model in all cases, it modifies the model and the modification is not guaranteed to be always good. Particularly if you had the model in its proper exact shape already (which is frequently how NURBS modeling works - the basic functionality of NURBS modeling involves making exact geometry, things like perfect spheres, carving precise holes in things, etc...), you would not want to apply sub-d do it because you would then mutate it.

If you want things to be kind of melty/lumpy then it's certainly fine, but if that's what you want then you probably should be using a poly modeler to create those types of models from the start. MoI is generally better suited and designed for making models that are well defined by profile curves, it's not focused on melty lumpy type model creation.

- Michael

So for example in this area of your model here:



I wouldn't be surprised if that topology there created a somewhat lumpy shape in that area. Probably not enough for you to notice it just looking at the wireframe or diffuse shaded render, but if you were to make that have a reflective material and then animate it, the reflections would probably squiggle around in that area instead of being very stable, while just exporting a mesh of the original model from MoI and not applying sub-d to it would give you a completely crisp and totally unwavering reflection in those same areas, as long as you got the good vertex normals coming through.

- Michael

Does exist strictly nurbs renderers?

Hi Pilou,

> Does exist strictly nurbs renderers?

You mean something that renders NURBS surfaces without turning it into polygons?

There are a few but it's not very common.

- Michael

< without turning it into polygons?
Yes :)

-> What would there be gained by applying sub-d smoothing

Hi Michael, most of the time I don't touch the topology exported by MoI but for example sometimes I find I need sub-polygon displacement on certain parts and I haven't planned at the start.

Marc