Paper card model from MoI 3D model?

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 From:  Mark Brown (MABROWN)
2392.1 
Hi Everyone.

I finally purchased my copy of MoI, more than a year after I first said I was going to do so. In the interim, my baby boy was born, somewhat diminishing the time I have available for 3D!

Over this period I have been considering ways to turn MoI creations (probably of ships) into physical models. One thing I want to try is creating a paper card model from an MoI design. Rhino seems to be used with great success for this by unfolding the 3D object to 2D. There is an impressive example of this here:

http://www.papermodelers.com/forum/ships-watercraft/71-hoche-french-pre-dreadnought-battleship-1-400-golden-bear-models-no-1-a.html

I realise MoI doesn't have inbuilt unfolding (any chance of a plugin API for MoI Michael?). Does anyone have any experience of using Blender's unfold script (or anything else) to do this? Can nurbs surfaces be unfolded or only polygonal meshes?

---
Mark
http://www.homepages.ihug.com.au/~mabrown/index.html

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 From:  Michael Gibson
2392.2 In reply to 2392.1 
Hi Mark, congratulations on your baby boy, and thanks very much for your MoI order!

> (any chance of a plugin API for MoI Michael?)

Yes, definitely in the future. But the main problem is that it tends to be a time consuming thing to both document and to also give support and help to programmers who are using such an API. So it tends to involve quite a lot more work than just creating the API itself...


> Can nurbs surfaces be unfolded or only polygonal meshes?

Only certain kinds of NURBS surfaces can be unfolded directly - those are ones called "developable surfaces", which basically only have curvature in one direction and have another direction straight, like a cone is one example. Otherwise something that has double direction curvature in it (like a sphere for example) cannot be unrolled into a flat medium without stretching being involved.

Polygonal meshes are built of flat faceted parts, so they avoid any issues with double curvature, it tends to make them more inherently easier to unfold.

So most likely you will want to export your model data to a polygon file format (STL or OBJ format will be most common for this) and then have the polygon data be unfolded.

One tool that you may want to check out is Lamina Design: http://laminadesign.com

It is a stand-alone program that is able to take in .stl or .obj polygonal files and will produce patterns you can print out and cut out from your card stock to assemble your model.

- Michael
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 From:  Alcides
2392.3 
Hello

Mark congratulations on your baby boy.

Well, I've registered here because I'm trying the look for more information on Moi. I'm trying the trial version.

My objetive is to find a cheaper alternative to Rhino to design paper models, I've made a search and I found this thread.

Mark, Michael has a misconception about the design of paper models. Paper can't be bent in two different directions at the same time, and there is always one straight direction on a bent paper.So, the solution is to design the model with developable surfaces.

We don't need a mesh unfolder, Rhino works great to design paper models because you can work with nurbs and Rhino has the function to unroll a developable surface. You can design a very clean and precise paper model with that tools. My only problem with Rhino is the price.

As I can see Michael isn't implementing this function in the near future, which is sad. I've found the use of Moi very intuitive and easy, but If I have to buy something like Lamina is to much money.

Regards
Alcides
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 From:  Michael Gibson
2392.4 In reply to 2392.3 
Hi Alcides,

> So, the solution is to design the model with developable surfaces.

This is pretty huge constraint, any general surface that is created by lofting, sweeping, revolving, etc... will not be developable - to only design with developable surfaces means applying various specific constraints to the way you go about designing your model.

MoI was not created with these particular specialized constraints in mind, so it would be a somewhat difficult task to achieve this result of only using developable surfaces with NURBS surfaces, using MoI anyway.

But if you do a conversion to polygons it basically removes the need to do this kind of specialized constraints in the construction of your NURBS models, so that is likely to be a much easier route for someone who is not going to be focused on spending a lot of time manufacturing their NURBS models.

If you are manufacturing things made out of cut steel, etc... then certainly that is another case and investing the considerable time that will be required to learn and train yourself to only model with developable surfaces would make more sense in that case.

- Michael
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 From:  Michael Gibson
2392.5 In reply to 2392.1 
In addition to Lamina Design, another one to check out is Pepakura Designer:
http://www.tamasoft.co.jp/pepakura-en/

It can take polygon data in a similar way as Lamina Design, looks like it supports OBJ, 3DS, LWO, and STL formats all of which are supported by MoI. I'd recommend trying OBJ format, but I'm not sure if it supports multi-sided polygons or not. You may need to adjust the option when you export from MoI, from Output: N-gons (which allows many-sided polygons in the generated OBJ file), to Output: Quads & Triangles (which only allows 3 or 4 sided polygons in the generated OBJ file).

- Michael
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 From:  Kurt (KURTF)
2392.6 
Lots of people are using Pepakura - then printing and cutting out the parts. They then assemble them, and coat them with Resin to make large sized parts. Here's a link to a Halo fan site with information on Pepakura fabricating:

405th.com
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 From:  Mark Brown (MABROWN)
2392.7 
Hi Michael, Alcides and Kurt,

Many thanks for your congratulations regarding the birth of my son. It is hard work but worth it all when he smiles :)

Thanks also for the responses to my questions. I have just tried blender's unfolder, which I'm probably not using correctly. I unfolded a simple cylinder. It made some very strange decisions regarding the unfolding, creating lots of little shapes. From experience, I know that Blender and I don't get on so I'm downloading Pepakura. Thanks Kurt for the tutorial link.

Michael, is MoI able to constrain a surface so that it is forced to be "developable"? For example, I'm thinking that for the sides of a hull, I could lay down an oversized flat surface, adjust it to fit the curvature I require and then trim the excess to abutt adjoining surfaces (did that make any sense?). Then, if I'm understanding what Alcides has said about Rhino, I unroll my surfaces (or perphaps a selection of surfaces?) rather than unfolding entire polygon meshes?

The Pepakura demo has just installed. Time to see what it can do...

EDITED: 12 Feb 2009 by MABROWN

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 From:  Michael Gibson
2392.8 In reply to 2392.7 
Hi Mark,

> Michael, is MoI able to constrain a surface so that
> it is forced to be "developable"?

Not in a fully general manner - for example there is not any kind of "force to be developable" checkbox that you can set.

However, I suppose it would be possible to enforce this yourself if you stick to only a few specific tools and operations that create developable surfaces.

Extrusions should be ok, also probably a sweep of a line segment along a path may do that. You may also be able to edit the points of an extruded surface (see this FAQ question for how to turn on points for some objects) and still maintain developability. You may need to use some kind of surface analysis tool to examine the Gaussian curvature of the surfaces you are working on to make sure they are developable.

In general though that is a pretty specialized requirement, MoI is not focused on that particular area of specialized modeling so if you need to create only developable surfaces you will probably be better off using a tool that is more specifically designed with that in mind - MoI's toolset is focused on much more general shapes.

If you convert to polygons though, that simplifies things a lot and you would be a lot more free to use any tools that you want in MoI and then send the polygonized output to one of those programs (Pepakura or Lamina Design).


> Then, if I'm understanding what Alcides has said about Rhino,
> I unroll my surfaces (or perphaps a selection of surfaces?)
> rather than unfolding entire polygon meshes?

Yes - if you wanted to work in this way you could use Rhino's "UnrollSrf" command which is able to calculate a 2D pattern from a developable surface (and only from developable surfaces). That is an alternate possible way to approach the problem rather than unfolding polygon mesh data. But in general you should probably expect to spend quite a lot of time learning many details about developable surfaces if you want to go this route, it tends to be more used by people who are going to construct their final object out of sheet metal.

- Michael

EDITED: 12 Feb 2009 by MICHAEL GIBSON

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 From:  Frenchy Pilou (PILOU)
2392.9 
Funny i have found this today :)
http://www.papermodelers.com

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 From:  Mark Brown (MABROWN)
2392.10 In reply to 2392.8 
Hi Michael,

Many thanks for the tips. I'm going to have a go at this over the weekend if the boy will give me time. I'm going to try to do this initially in a developable way I think, more in keeping with the actual material. My thinking is that a hull is basically a cylinder shape at midships and various tapers or cones towards bow and stern, trimmed to conform in the horizontal plane (that probably didn't make any sense either!). I will still have to do the unfolding from a polygon model as I don't have access to Rhino. Even so, I'm guessing I'm going to get a cleaner unfolded shape by staying as close as I can to a developable surface.

> Not in a fully general manner - for example there is not any kind of "force to be developable" checkbox that you can set.

Would such a check box be a possibilty for a future version of MoI?

---
Mark
http://www.homepages.ihug.com.au/~mabrown/index.html

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 From:  Michael Gibson
2392.11 In reply to 2392.10 
Hi Mark, it sounds like you're on a good track for trying it out anyway!

> Would such a check box be a possibilty for a future version of MoI?

It's not really too likely.... This is a pretty specialized area and it is not an area that I personally have a whole lot of particular experience in. So it just is not really a great match for MoI.

Also it is a big goal for MoI to stay simple and easy to use and understand. Each kind of specialized option that gets added in will have a tendency to clutter the UI and make it incrementally harder to understand for someone who doesn't need that option. There can actually be negative consequences to adding in too many things, that's something I am pretty worried about in general.

- Michael
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 From:  Mark Brown (MABROWN)
2392.12 In reply to 2392.11 
No worries Michael. I fully understand your concerns regarding feature creep.

I have been playing with export of a hull form to obj and have been reminded of how good the polygon conversion is. I'm quite confident this can be done with a bit of careful design and selective mesh unfolding.

---
Mark
http://www.homepages.ihug.com.au/~mabrown/index.html

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