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hole in a metaball object

thoromyrthoromyr Posts: 452
edited December 1969 in Carrara Discussion

I don't normally use metaballs (nor meatballs, if I miss an auto"correction"), but in playing with it today for an animation I ran into an oddity: for a few frames one of the balls has a hole clean through it. I can't for the life of me figure out why or how and I'm hoping someone has an idea so I can fix it.

I've attached a couple of images. One is a quick render in the assembly room, the other is in the modelling room and shows several holes in the metaballs. Perhaps more apparent when dollying around than in a still image, but there appears to be a smaller set of the meatballs inside the larger. To be honest, I don't know how much I trust the view in the model room as it has often been displaying the meatballs incorrectly. Like leaving a "blob" in 3d space when shifting time on the sequencer or moving/resizing some of the balls.

Screen_Shot_2015-01-25_at_8.07_.52_PM_.png
661 x 352 - 96K
Screen_Shot_2015-01-25_at_8.06_.24_PM_.png
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Comments

  • JonstarkJonstark Posts: 2,738
    edited December 1969

    A guess, but I suspect you've got a negative metaball loose in your scene somewhere. Their whole purpose is to 'subtract' from the positive metaballs, and judging from the shape I'll bet anything it's a negative metaball sphere that's loose in there.

  • thoromyrthoromyr Posts: 452
    edited December 1969

    Thanks for the response. I'd thought of that, but negative metaballs are shown by default, and are selected to be shown, and wouldn't have this result in any case: they subtract space, but do not remove surfaces. You can see in that screen shot that it isn't a hole with a surface, it is missing surface.

    So, combined with the fact that no negative metaball is shown in the space where there is a hole and that it would leave a surface behind from the cutting, I do not see how it can be a negative metaball. (In addition, both of the ones I've added are visible and accounted for.)

    Any other ideas?

  • JonstarkJonstark Posts: 2,738
    edited December 1969

    I'll be the first to admit I'm no expert with the metaball modeler :) I was playing with it for the first time ever just a little earlier this week, but I do remember noting how easy it was to accidentally add something I didn't know was there, that and the shape of the hole immediately made me think it was possibly a negative ball. Hopefully someone who is more expert with metaballs than I am will see this and provide a more helpful comment.

  • WendyLuvsCatzWendyLuvsCatz Posts: 37,927
    edited December 1969

    funny how everyone does teddy bears

  • DartanbeckDartanbeck Posts: 21,248
    edited December 1969

    Jonstark said:
    I'll be the first to admit I'm no expert with the metaball modeler :)
    Nope!
    That's a time-honored admission in this forum! ;)

    Sorry thoromyr, I'm at a loss as well. Cute little bear, though!

  • thoromyrthoromyr Posts: 452
    edited December 1969

    Why a teddy bear? I'm not really sure. I think it was illustrated in the manual for metaballs, but I wasn't even looking in the manual for that. What I have in mind is more than just teddy bears though.

    In any case, one thing that struck me was that it was rather like the metaball in question were being cropped as by a bounding box. Except that:

    1) I'd expect a bounding box to be a cube and only the top and bottom of the sphere was cropped

    2) the metaball just keeps growing, but the hole only lasts for a second or two

    However, I thought it worth a shot so I set the time to where the hole appeared and shrank the metaball a bit. It still grows to its final size, just not so big at that point. And... a spot check showed the hole going away.

    I'm re-rendering the animation now. I still don't know why the hole appeared, but it does appear to have something to do with scaling.

  • DUDUDUDU Posts: 1,945
    edited December 1969

    I'm ready to bet that you will not have these holes in your render…
    Isn't a problem of camera focus ?

  • Design AcrobatDesign Acrobat Posts: 459
    edited December 1969

    Maybe you accidently selected a negative cylinder object? Doesn't look like it though, it's a high fidelity Boolean cut. Undocumented feature? :)

    cylinder_blob_primitive.jpg
    450 x 440 - 48K
  • thoromyrthoromyr Posts: 452
    edited December 1969

    @Design Acrobat: as your own screenshot shows: negatives are visualized and don't destroy the surface.

    @Dudu: it looks fine *except* for the render. Doing spot renders in the assembly room is a good way to do spot checks like this. Click the camera icon on the left hand side, drag a rectangle and carrara will render just that spot.

    Daz has acknowledged the bug and are looking into it.

  • DUDUDUDU Posts: 1,945
    edited December 1969

    thoromyr said:
    @Design Acrobat: as your own screenshot shows: negatives are visualized and don't destroy the surface.

    @Dudu: it looks fine *except* for the render. Doing spot renders in the assembly room is a good way to do spot checks like this. Click the camera icon on the left hand side, drag a rectangle and carrara will render just that spot.

    Daz has acknowledged the bug and are looking into it.

    Sometime (rarely), the quick render doesn't give really what it will be in the final render.
    E.g. if you use footages in your textures, or if your camera is too close to an object, but also with the metaballs.
    I'm a large user of animated metaballs and I often have this problem, I must sometimes even close the program and start it again to restore a normal sight in the metaballs room.
    I thought of that when you said that you didn't have any negative metaballs.
    Is it in C8.5 ?

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