Boolean

Question

Hello! I get an unexpected result (to me, that is) for the Boolean when I rotate in a certain way

Can someone explain the result (the red area, you know what I mean :) for the circle at the origin?

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Reply
  • Omar Domenech replied

    I guess it's the usual answer of, Booleans are super finicky and unpredictable and do all sorts of unpredictable things. I take it as a given and just go with the flow, but if you're more of the technical oriented mind, I guess it can be frustrating and you'd want to understand. Maybe Martin knows the technicality behind it. 

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  • Grady Pruitt(gradyp) replied
    It looks to me in the first one, the cut is happening below the top surface. If you hide the one being used to cut out, you can see the result of what is going on.
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  • Grady Pruitt(gradyp) replied

    (I am watching from my phone, so I might be missing something)

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  • Martin Bergwerf replied

    Hi Tom,

    Simply put, that is a rounding glitch.

    The Z value in the second example is 0.0... and that is exactly 0. The Z value in the first example is 0.5 and that is not written exactly as 1/2 in binary, but written as a floating point notation and that is not exact for 0.5 so it has to be rounded.

    Here's an interesting video, that explains some of the problems with floats (it's about computers, not about Blender): 

     https://www.youtube.com/watch?v=y-NOz94ZEOA 

    EDIT: 0.5  should be -0.05, but the principle stays the same.

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  • Tom Fransson(tfsuper3d) replied

    Yes Omar, I have understood from reading other threads about the Boolean, that it can be abit finicky and that some cleanups is have to be done after applying. I haven't used Boolean that much myself, this was facing me after playing around with it abit after helping a friend with a Boolean issue. So it is not a big deal, just curiosity. Uhm Grady, I'm not sure but I'll take a closer look. Thank you both

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  • Tom Fransson(tfsuper3d) replied

    Oh, thanks Martin

    • 👍
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