Modeling to create flat patterns for inflatables or stuffed animals.
Since Tom Foster's sheet metal problem inspired a lot of ideas, I will try another problem that needs some brainstorming.
I want to design the pattern for some inflatable figures. These are made from fabric that is sewn together, and then inflated with a fan. You often see them in people's front yard during Christmas and other holidays.
If you have a 3D model made from a mesh, there are programs that will unfold each facet to create the flat pattern. Some are free, and others like Pepakura are fairly inexpensive at around $50 USD. Another example is the free "Paper Model" add on to the Blender software.
But, these are geared towards creating a paper model, rather than an inflated or stuffed figure, and there are several issues with using them for a cloth pattern.
1)They also need a fairly simple mesh, because a mesh with a lot of facets will result in a pattern that is unusable because of the large number of pattern pieces it creates.
2)The problem with using this faceted model for a cloth pattern, is that each corner of the facet tends to form points in the finished object, which also tend to wrinkle. And perhaps it can be used as a guide to create a more refined pattern, but there is one more issue.
3)Inflated or stuffed animals always try to go to their maximum volume. The resulting surfaces are always either a sphere or a part of a cone or cylinder. And since flat material, unless it stretches significantly like latex, cannot make a true sphere, we are left with surfaces that are always either a cone or sphere.
The above two issues mean that most 3D models available on the internet are useless for creating inflatables or stuffed animal patterns.
Now, in regards to the methods of creating the pattern, there is another approach used in the Rhino CAD program. Since it is a surface modeler, surfaces are defined by splines. From what I have read, its unfold utility "unrolls" two splines that form the edge of a surface. This approach is more accurate.
It may be possible to approximate the "unrolling" approach by modeling each portion of the mesh that will make a pattern piece, is defined by a series of slender facets, that perhaps look like ladder rungs, with the sides of the ladder being the curve. This would resolve the problem #2.
Problem #3 requires that you take a special approach to creating the model from the start. Here is where I am lost. Does anyone have ideas about how to approach creating a model like this? I suspect that Blender is the better software to create my model, but I would prefer not to have to learn a complex program, and would prefer to stay in BricsCAD because I know it very well.
Thanks for any suggestions,
-Joe
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Have you tried unfolding the facetted pattern and splining the edges to make them smooth ? ( not shure this would do it)
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I am afraid that I don't understand what you are suggesting.-joe0
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Hey Joe,
some years ago I worked on this cow. I wrote a program to find "ribbons" and than I unfolded them. But as there where no interest in these ideas I finished this work.
In case of interest you can contact me via www.ant-ares.de
Regards
Jochen
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I believe I played with your program at some point in the past. There are a number of programs available now, that are capable of unfolding the kind of strip that you show.It seems the real challenge is in making a mesh that the program can use to generate a useful strip, and no one has solved that difficulty... at least not without learning a program like Blender, and re-doing the mesh so that the facets are located appropriately for where the seams should be.-Joe0
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Joe your ladder rungs approach is basically the way they make yacht sails and many or most sailmakers use specialist software to design sails and develop the panels/wide strips.
The same basic construction was used before computers, but I don't believe vanilla 3d programs offered any real shortcuts.
Yacht hulls have a similar challenge (and similar specialist solutions) - a friend who uses Archicad drew the panels for a 'stitch and glue' dinghy class, but he drew them from the trial and error original boat. Developing them in space didn't seem to be an option, or else it was too hard.
Amateur comments from a 3d drafting perspective, but that's a 'field' experience from industries with a similar challenge to yours.
Except inflatables and stuffed toys rely a lot on stretch.0 -
Actually, the rip-stop nylon does not stretch at all. It is coated to make it relatively air tight, and even reduces the bias (diagional) stretch.I actually started to develop the pattern for my project, by using a few old-fashioned drafting techniques, even if I used the computer. Half of the challenge of pattern development for cloth is knowing where to place seams, and that just comes from experience.I have a lot of puppet making experience so I am used to working with sheet foam and gluing the edges with contact cement. I was thinking I would just print out the pattern as I have it now, and then make a full-sized version of it in foam. The benefit of the foam is that it tends to round-out like it would if it were inflated. Also, it is very easy to cut new darts, and then glue them closed. And when you change your mind, cut them back apart and re-glue the dart back in. After I am finished with the test pattern, I would cut it back apart and then trace it back into the computer.However, the size of the item is a problem. I want to make a double-life-size camel for the final version I was going to make my test camel the full size of an actual camel. But, that is not something that I can use my 11x17 scanner to digititze, even if I did multiple scans. It is just too large. I am thinking I may tape the pattern pieces to a wall, and then take a picture with a camera from as far away as I can. I have a friend with a professional digital camera that has a zoom lens That should reduce the distortion and also give me good resolution.For those interested, I did find other software.Pepakura, can only unfold, and cannot create models. $38 USD.Rhino, $1,000 USD.TouchCAD, a full modeling and unfolding system that is very well developed. $2,000 Euros.EasyToy and PatternImage (one for modeling and the other for unfolding. The "EasyToy" is quite cheap, but its unfolding addition is $4,000 USD.Also, here is a paper from a Disney research team on the subject of automatically extracting a viable pattern from a complex model.-Joe0
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Joe if I with my limited Cad abilities had to tackle that, I'd come at it from a real life stuffed animal from a junk shop or second hand etc, dismantle it, scan and scale appropriately.Sounds simple, but my wife and I have played about with this approach, albeit not on such a grand scale.Just my 2 bobs worth.0
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I actually did some thrift store shopping for just that reason. However, stuffed animals are often cartoony, and I need it realistic. Also, camels are not very common. I did get a stuffed horse so that I would have something that was an example for where to draw the pattern lines. Besides, I would not want to ignore the stuffed animal designer's copyrights and duplicate it exactly.-Joe0
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An alternative to Blender might be Rhino, which is geared towards this type of thing. It can also flatten curved profiles, although I've only seen it down with boat hull profiles. Rhino can export to .dwg, so if you new someone with it, they could generate the model and export out to BricCAD for you.
Within BricsCAD surfacing tool options aren't available natively, but you could potentially:- You can use Konstantin's SWEEPX/LOFTX suite of tools to generate these type of objects.
- You can lever off ClipBoardFormat to convert an ACIS Solid/Surface to a Mesh.
- Use a tool like Jochen's to flatten, or export to Blender.
Regards, Jason Bourhill CAD Concepts0
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