Comment on Are there any volume fit calculators?

HelloRoot@lemy.lol ⁨1⁩ ⁨day⁩ ago

• MysteriousSophon21@lemmy.world ⁨3⁩ ⁨hours⁩ ago

  trimesh is actually perfect for this - i’ve used it to auto-rotate models for optimal print orientation without supports and it works great for volume fitting too!

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• tal@lemmy.today ⁨1⁩ ⁨day⁩ ago

  The best methods we have (afaik) basically randomly position the object and then nudge it until it gives up after doing lots of tries

  I’m skeptical. I can think of some problems that do work like that, like graphviz’s node-cluster-and-fit-to-a-plane layout stuff. But here, you should just need to be working with the convex hull. It should be possible to eliminate a lot of classes of potential solutions by reducing it to looking at edge cases, like some face of the convex hull is in-plane with the bounding box or something.

  kagis

  Yeah.

  en.wikipedia.org/…/Minimum_bounding_box_algorithm…

  In computational geometry, the smallest enclosing box problem is that of finding the oriented minimum bounding box enclosing a set of points. It is a type of bounding volume. “Smallest” may refer to volume, area, perimeter, etc. of the box.

  It is sufficient to find the smallest enclosing box for the convex hull of the objects in question.

  In 1985, Joseph O’Rourke published a cubic-time algorithm to find the minimum-volume enclosing box of a 3-dimensional point set.

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  • HelloRoot@lemy.lol ⁨1⁩ ⁨day⁩ ago

    Have you read the algo?

    It basically takes the global minimum over all edge pairs (and their zero-curves) and return the orientation and extents with the smallest encountered volume. Which is basically like trying every possible position along the edges of the convex hull around your obect.

    But I edited my comment to remove that part, because that bit is honestly irrelevant for OPs question.

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    • tal@lemmy.today ⁨1⁩ ⁨day⁩ ago

      It’s not the nudging that you referred to. You edited your comment after I responded to remove that part of your comment.

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      • HelloRoot@lemy.lol ⁨1⁩ ⁨day⁩ ago

        I edited it before I read your reply.

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  • Blue_Morpho@lemmy.world ⁨1⁩ ⁨day⁩ ago

    because 3D printers have their own constraints in things like the overhang that they can do.

    That’s what supports are for. :) In my case I made a custom sprue because autogen supports sagged unless it was 0 clearance.

    I was just looking for something like a rectangular prism or cylinder to fit in a cube. I was surprised by the replies that it’s mathematically hard. I expected it to be a geometry problem with a bit of calculus to find the convergence.

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