Altering or deforming Moi objects in a polygon app (C4D)  1-20  21-26

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 From:  nycL45
3238.1 
OT? This is a question maybe best discussed in a C4D forum but there are few Moi users there while I expect a greater concentration of polygon app users here.

Michael has noted this about deforming and nurbs modelers, "...it is a pretty difficult thing to make solids deform and still keep joined edges within a good tolerance". Maybe in version 4.

What is the best process for altering or deforming Moi objects exported as .obj in C4D? Is it practical? Or, is it best to model objects that need altering or deforming in the poly app and (Gasp!) not use Moi? Is there anything that can be done while modeling in Moi to improve altering and deforming later?

I understand Moi's normal tag becomes useless once any action changes the object such as subdivide or using the knife tool. When I subdivided a Moi object there were coupled black and white polys covering it. The normals were okay. Also, the isoparms (?) looked like ridges on what was a smooth surface. Nixed for rendering.

Any thoughts?

Leonard
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 From:  WillBellJr
3238.2 In reply to 3238.1 
Interesting question.

I typically use MoI for mechanical models which typically don't require deforming that much except for things like screw threads, spiral staircases etc., but even those can be constructed in MoI sans deformations without too much fuss.

Unless you're exporting quads & tris or strictly tris, NGons aren't too friendly with bend and twist operations so just like with NURBS, you may still be stuck depending on your poly app.

The best (time consuming) advice I can offer is to create your base objects in MoI and then perhaps retopologize them using say TopoGun or 3D-Coat (or a plugin) down to a pure quad (something that is SDS modeler friendly) or triangle topology.

Then you should be able to perform any kind of bend, twist, etc., operation your modeler supplies.

Granted you can get quad/tris or straight tris out of MoI directly if you're not too concerned about the resultant topology.

-Will

PS - C4D has some great deformation operators but I still believe you need to eliminate all ngons before you can expect to get workable results.

Now if your ngons are away from the areas being deformed, then sure, give it a try. Subdivided objects are best for deformations and like I suggested, only manual retopo will get you the pure quads you need for subdivision from your base objects.

EDITED: 13 Jan 2010 by WILLBELLJR

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 From:  Michael Gibson
3238.3 In reply to 3238.1 
Hi Leonard, yeah it can work fine to deform OBJ output from MoI as long as you prepare the output for it by dicing it up into small evenly sized polygons. That's done by using the "Divide larger than" option at mesh export time.

Here's an example PaQ posted some time ago with an object exported from MoI and deformed in Modo:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2704.17


When you enter in a distance for "Divide larger than", it will cause any polygons larger than that size to get split up into smaller pieces.

Once there are numerous vertices distributed more evenly throughout the structure it will be able to be deformed properly in a polygon modeler. That's because a polygon modeler usually deforms objects only by moving their existing vertices around and if your vertices are more sparsely distributed across the model it will not deform well. By default MoI produces that kind of sparser vertex structure because it reduces data size for regular (non-deforming) rendering.

I'm not entirely sure if the true vertex normals will be used after the deform or not - if you are deforming the entire object instead of some portion of it, it is possible that the normals could get deformed as well and remain intact but it is somewhat more likely that they will be discarded and recalculated by an averaging of adjacent faces. But if you have small diced up polygons it can help to reduce shading errors that tend to come from that averaging process as well.

Check out some of these previous posts to see some illustrations of how you want the output to look when you use "Divide larger than" :

http://moi3d.com/forum/index.php?webtag=MOI&msg=2833.5
http://moi3d.com/forum/index.php?webtag=MOI&msg=1084.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=1549.4
http://moi3d.com/forum/index.php?webtag=MOI&msg=804.26

- Michael
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 From:  Michael Gibson
3238.4 In reply to 3238.2 
Hi Will re: N-gons - certainly large n-gons that traverse a fairly large area of your model are not good for deformation.

But actually neither are quads or triangles that span a large area of the model - since a polygon modeler usually only deforms the existing vertices of a model, you need to have plenty of vertices throughout the shape, even if it is made up of 100% quads or 100% triangles with no n-gons at all.

That's because a polygon modeler usually only deforms existing vertices in the model. So for example with a twist, only vertices get twisted, not really the polygon surfaces themselves. The polygons remain as straight pieces connected between the vertices.


So it's more of the "span a large area of the model" that is really bad for deformation, not quite so much the "n-gon ness".


But also N-gons do not behave well if they become warped to be significantly non-planar which then makes triangulations of them ambiguous. But they are not necessarily a problem if they are small enough in size so that no individual one is getting warped to a very large degree.


For example see this previous post where PaQ is showing an n-gon model that is being warped inside of Modo with no problems:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2704.17


However, if you do suspect that some individual n-gons are going to get warped to become fairly non-planar then it can be better to avoid them and use "Export: Quads & Triangles" instead so that the polygon structure is all fixed in place from the start.


- Michael
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 From:  nycL45
3238.5 
Hi Michael, PaQ's creation is very encouraging. I would like to see a pre-Modo version to get an idea of how much sculpting he did in Modo.

I did set the Divide larger than but probably not fine enough, fearing that too fine a setting would make the file very large. If I use your setting of 0.5 then I should not need to subdivide in C4D.

So, you are saying that Moi objects exported with small diced up polygons should be just fine for normal sculpting. I will work on it right now and be back if there are problems.

Will, thanks for your suggestions and thoughts.

>only manual retopo will get you the pure quads you need for subdivision from your >base objects.

Manual retopo? eeeek!

I will check into TopoGun; it has been mentioned a few times in some forums

Thanks.

L.
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 From:  Michael Gibson
3238.6 In reply to 3238.5 
Hi Leonard,

> I would like to see a pre-Modo version to get an idea of how
> much sculpting he did in Modo.

Check out the next message down in that same thread, where there is a screenshot of the original model:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2704.18

I think he probably used some kind of bend transform on the whole object and not individual vertex level adjustments if that is what you mean by "sculpting" though.


> So, you are saying that Moi objects exported with small diced
> up polygons should be just fine for normal sculpting.

Well, yes - small diced up polygons should allow objects to be deformed with various things like "bend", "twist", etc...

What exactly do you mean by "sculpting" though, are you talking about some particular tool in Cinema4D?


> I did set the Divide larger than but probably not fine enough,
> fearing that too fine a setting would make the file very large.

Yes, it will probably make the file pretty large which is why it does not generate output like that as the default.

But unless you have like a 10 year old computer you should be able to handle a pretty large file ok.

- Michael
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 From:  WillBellJr
3238.7 
"Manual retopo? eeeek!

I will check into TopoGun; it has been mentioned a few times in some forums..."


True, I agree, it seems like twice the work but unless you're really good at straight poly modeling, I find creating concepts in MoI to be much faster than when working at the polygon level - that's just me.

Perhaps it balances out - time saved in initial model development, time spent in retopo to get an optimized mesh that can be SDS'd or that fit into a polygon budget for your game engine etc.


-Will

PS- Also take a gander at 3D-Coat as well if you've never tried it, it's pretty decent for what features it has.

EDITED: 14 Jan 2010 by WILLBELLJR

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 From:  nycL45
3238.8 In reply to 3238.6 
Hi Michael,

> Check out the next message down in that same thread,
> where there is a screenshot of the original model:

OMG! + Duh. Wow, that makes PaQ's Modo model amazing. Ah, a bend transform. I thought perhaps he used "individual vertex level adjustments" = "sculpting".

> What exactly do you mean by "sculpting" though, are you
> talking about some particular tool in Cinema4D?

Yes. One way to make wrinkles in C4D is to make cuts with the knife tool, set a bevel to the edges and pull the edges. Also, I want to take portions, areas or sections of vertices and bend them. The idea is to make the "perfect" object look used such as the chaise longue headrest below.

As far as file size, my three year old does pretty well. :-)

Leonard
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 From:  nycL45
3238.9 In reply to 3238.7 
Hi Will,

I certainly agree with everything you said. I will check out 3D-Coat.

Thx.

Leonard
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 From:  Frenchy Pilou (PILOU)
3238.10 
And if I you have no money (export from moi in skp format)
http://sketchup.google.com/intl/en/
Google Sketchup has some tools for some twisting and bending volumes :)
http://www.youtube.com/watch?v=bPbb8PPGtVg
http://www.youtube.com/watch?v=tGHTIOMm_34
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 From:  Michael Gibson
3238.11 In reply to 3238.8 
Hi Leonard,

quote:
Yes. One way to make wrinkles in C4D is to make cuts with the knife tool, set a bevel to the edges and pull the edges. Also, I want to take portions, areas or sections of vertices and bend them. The idea is to make the "perfect" object look used such as the chaise longue headrest below.

It can be better to try and use displacement or bump mapping at render time to do that rather than modeling little bumps directly.


For many situations the output from MoI will not be very well suited for individual vertex level manipulation, but for your particular case where your headrest has a simple structure made up of one larger surface, that will probably generate some good output for vertex manipulations in that particular area of your model, because the mesh will have a nice regular topology in there.

If you want to do a lot of individual vertex adjustments right in an area where there are many edges and surfaces coming together in different ways (like at booleaned intersections), then those places are not as good for vertex editing and that's when you would probably need to think more about retopologizing, or possibly creating the model in polygons from the start with a vertex adjusting friendly topology from the beginning.

For your headrest though that should be fine I think with just a denser mesh generated by using "Divide larger than".

If you want to only generate a dense mesh on just the headrest, you can select it and use File > Export to write just the headrest to an OBJ file - Export will only write the selected objects to the mesh file.

- Michael
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 From:  nycL45
3238.12 In reply to 3238.10 
Hi Pilou,

You can imagine the wrinkles that are necessary to make the headrest above look used and how the ends would be angled in due to the weight and shape of head on the center section. I could be wrong but I think the knife or magnet approach would be used for wrinkles and deforming tools to "bend" the ends inward.

Leonard
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 From:  nycL45
3238.13 In reply to 3238.11 
Hi Michael.

> It can be better to try and use displacement or bump mapping at render time to do that rather
> than modeling little bumps directly.

Zbrush, 3D Coat, etc. for the wrinkles and deforming for tilting the ends inward.

> ...but for your particular case where your headrest has a simple structure made up of one
> larger surface, that will probably generate some good output for vertex manipulations in
> that particular area of your model, because the mesh will have a nice regular topology in there.

> For your headrest though that should be fine I think with just a denser mesh generated by using
> "Divide larger than".

I think you are right despite the strange results from my first attempt. I will export a number of
headrests with varying densities and do some local cuts.

Thanks,

Leonard
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 From:  Michael Gibson
3238.14 In reply to 3238.13 
Hi Leonard, if you were getting some strange initial results, you may not have divided the polygons up to a fine enough degree.

Don't be so hesitant about it, especially if you are selecting just the headrest and using export, get it diced up into really a whole lot of little tiny pieces and that will deform better for you.


> Zbrush, 3D Coat, etc. for the wrinkles and deforming for
> tilting the ends inward.

Yeah those are good tools for doing that kind of a thing.

For ZBrush you should try to dice it up into pretty small pieces.

For 3D-Coat if you are using the Voxel painting mode, you actually do not need to dice it up so finely for that case because 3D-Coat's Voxel mode does not use the polygon vertices directly for deforming, it converts the polygons into voxels and then the voxels are deformed. So for that particular mode you don't need to have to have diced up polygons as much.

- Michael
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 From:  nycL45
3238.15 In reply to 3238.14 
Hi Michael. I have not gone through the multiple exports with varying settings. The original headrest export had Divide larger than = 2 and the polygon slider set at 8. I plan export with settings for Divide larger than settings at .25, .5, 1, and 1.5. Hopefully this afternoon.

I will post the results.

Leonard
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 From:  nycL45
3238.16 
Hi Michael,

I was playing with the headrest mesh and noticed triangles appearing in rendered areas. The only modification to the mesh has been made with the C4D magnet tool. Is this from Moi or is it a C4D issue? Is there a correction?

A C4D v10.5 file is attached. The Moi export settings were Angle 20, DLT .5 (Tessellation can be seen with Angle at 20.)

Leonard
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 From:  Michael Gibson
3238.17 In reply to 3238.16 
Hi Leonard, that looks like a polygon modeling issue - if you're going to grab just a single vertex and pull it around you may want to export as all triangles rather than as n-gons. Or C4D also probably has a triangulation command that you could apply to it inside of C4D.

N-gons made up of many points do not behave very well if they get some points warped so that the n-gon is not anywhere close to planar anymore. It makes the triangulation of the n-gon to become ambiguous.

Check out this polygon modeling video tutorial for an illustration:
http://guerrillacg.org/home/3d-polygon-modeling/multi-sided-polygons


So that's probably the main thing you're running into.

You may also want to generate an even denser mesh than what you show there.

- Michael
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 From:  nycL45
3238.18 In reply to 3238.17 
I think you are spot on, Michael. I used the Magnet "needle" in that area. Staying with dome, ball or circle seems to work just fine.

The pic below shows what trangulate does for the mesh.

> You may also want to generate an even denser mesh than what you show there.

To avoid the tesselation up close, A=12 or 10. DLT=.25? Finer???

Thx.

L.
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 From:  Michael Gibson
3238.19 In reply to 3238.18 
Hi Leonard,

> The pic below shows what trangulate does for the mesh.

You may want to export as Triangles directly out from MoI for a case like this. MoI's triangulator will put center points in for n-gons that can be triangulated in a radial manner, which can help to reduce some of the more skinny triangles.


> To avoid the tesselation up close, A=12 or 10. DLT=.25? Finer???

It's not so much for "up close" shots, but more that smaller polygons will reduce shading artifacts.

Remember - polygons are not actually smooth at all, they are only little flat pieces and the shading is done by a kind of trick.

If your polygons have too much variation between each adjacent one, that can tend to cause shading artifacts where the smooth shading trick does not work as well to make those flat pieces appear as if they were a smooth surface.

- Michael
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 From:  nycL45
3238.20 In reply to 3238.19 
Hi Michael, I exported triangles at Angle = 10, DLT = .25. The shading artifacts are there. I used the Magnet "circle" setting with the radius matched to the headrest but pulled a lesser distance. It appears to torque the edge polys too much.

> If your polygons have too much variation between each adjacent one, that can tend to cause
> shading artifacts where the smooth shading trick does not work as well to make those flat
> pieces appear as if they were a smooth surface.

Leonard
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