Unfolding rounded shapes

Discussion in 'Software' started by sruch, Jun 3, 2004.

  1. sruch

    sruch New Member

    Do any of the unfolding programs like Pepakura have the ability to unfold rounded shapes or do they only handle flat faces.

    Also, can any of the low-priced CAD software packages generate rounded shapes?

  2. wunwinglow

    wunwinglow Active Member

    Hi Steve,

    aha, you just hit the nail right on the head....

    3D models come in two distinct families.

    Mesh models, such as those generated by 3DMax, Wings3D, are composed of a list of points in a 3D space, with triangles drawn between the points to indicate the surface of the model. As such, the model is made of lots of flat panels, and unfolding programs such a Pepakura attempt to hinge all those triangles into a single flat surface. Where the geometry would mean these triangles would overlap, the model is broken into seperate pieces to avoid this happening. To simulate a smooth curving surface, lots of little triangles are used. Great for accurate rendering, but it makes unfolding such a model many times more difficult.

    Surface models, NURBS models and other similar forms use mathematical formulae to describe surfaces, how they curve, how they are trimmed and joined to form the final shape. This allows virtually any surface you require to be modeled. However, to open them out flat requires that they only curve in one direction; peel an orange and try to open the skin out flat; can't be done without stretching or splitting it! I'll plug Rhinoceros at www.rhino3d.com as a great example of a NURBS modeler. It has some excellent unfolding tools.

    Bottom line, if you are designing a model intended to be opened out into a paper cut-out, you must take that into consideration when you build it, whether it is a mesh or a surfaces format.

    Regarding rounded shapes in cheap/free software packages, oh yes, they can do that!! As the price/complexity goes up, the extra functions usually allow quicker, maybe one-click solutions to some construction process, but even the cheapest free-est software packages are capable of producing excellent results; it is down to the individual modellers willingness to practise and learn the software, and use his/her imagination, that leads to a fine design! And that goes for ALL software!

    Check out www.wings3D.com . D/L the free software and the pdf manual, and have a go. Frustrating, yes. Baffling, yes. But when it all starts happening for you, rewarding, YES!

    Tim P
  3. Gil

    Gil Active Member

    Hi Steve,

    Yes, Pepakura will unfold a sphere..., I just tried it just to make sure. Used True Space to make a sphere. Saved it as a .dxf file and opened it in Pepakura and unwrapped it without a hitch (see screen shot below).

    Most 3D Nurbs based programs allow you to "weld" seams together. A welded seam cannot be unfolded by the unwrapper but if not used intelligently can put you in a class of modern art all by yourself as the unwrapper attempts to "flatten" the impossible.

    One word of support in your efforts..., if it seems impossible tonight, sleep on it and read the manual or better yet, go to the user's sight and see if the subject has come up before. Tim is right about it all finally falling together, when it does you'll understand just what he means. I've had the same epiphanous experience with several packages (lots of sleep in the beginning though)...,

    Best regards, Gil

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