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How can I create a plane perpendicular to the long diagonal of a cube? I have this which isn't correct.

pic

Animation of plane perpendicular to the long diagonal of a cube (it should look like this). Animation plane perpendicular to the long diagonal off a cube

Animation with audio of why. https://youtu.be/fWsmq9E4YC0?t=118

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You can create a face-type Custom Orientation from any 3 points:

  1. Edit Mode: Select the 3 points you want the plane to be aligned to and create a Custom Orientation from them.. ensure it's being used.
  2. Object Mode: Select the plane, and Object > Transform > 'Align to Orientation'.

enter image description here

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    $\begingroup$ This is the correct answer, but you have to use differents points for the orientation. $\endgroup$ Nov 10 '21 at 16:45
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    $\begingroup$ Robin? Does that give the good solution? $\endgroup$
    – lemon
    Nov 10 '21 at 18:09
  • $\begingroup$ @lemon ... ahhh... Hope that's better, if that's what you mean.... $\endgroup$ Nov 10 '21 at 18:36
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    $\begingroup$ Robin, yes. Many wrong upvoted answers here... but now that's ok $\endgroup$
    – lemon
    Nov 10 '21 at 19:00
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    $\begingroup$ Glad to see the best answer poping first :) $\endgroup$ Nov 12 '21 at 10:54
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To rotate the plane so that it is exactly perpendicular to the long diagonal of the cube, one can use either a constraint or a little bit of trigonometry.

Constraint

With the plane centered on one of the corners,
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Add a Track To constraint and set the target to the cube.
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Trigonometry

Alternatively, one can use a short python expression to find the correct rotation.

First, rotate the plane around either the X or Y axis using the expression atan(2 / sqrt(2)) * 360 / tau.
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Then, rotate the plane 45° around the Z axis.

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    $\begingroup$ OMG ....are u math professor or why is this "a little bit of trigonometry"? +1 for "a little bit" ;) $\endgroup$
    – Chris
    Nov 10 '21 at 6:07
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    $\begingroup$ Two good solutions and the only ones to be exact here! $\endgroup$
    – lemon
    Nov 10 '21 at 18:08
  • $\begingroup$ only ones until Robin updates his answer... ;) $\endgroup$
    – lemon
    Nov 10 '21 at 19:28
  • $\begingroup$ @Chris Nope, not a professor. I hate math class XD $\endgroup$
    – HISEROD
    Nov 10 '21 at 21:46
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use math, cube is rotated to xyz axis correctly, create plane that is rotated correctly as well by default. Now, rotate it by 45 degrees on Y axis (or X), rotate it again on Z axis by 45 degree...

You end up with this and it is in right position. Set your orientation to Normal:

Now when you move with G+Z it will go this way

enter image description here

Now you just need to animate it on this movement and make it boolean cutter

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  • $\begingroup$ +1 sounds for me like the easiest solution... $\endgroup$
    – Chris
    Nov 10 '21 at 6:08
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    $\begingroup$ 45 and 45 does not work $\endgroup$
    – lemon
    Nov 10 '21 at 18:09
  • $\begingroup$ did you rotate it in right order? $\endgroup$
    – MikoCG
    Nov 11 '21 at 5:03
  • $\begingroup$ @MikoCG, yes. Have a look at HISEROD answer where the good angles are provided. $\endgroup$
    – lemon
    Nov 11 '21 at 9:28
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Rotate the plane 45deg on both X & Y axis, then snap to the vertex of the cube.

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    $\begingroup$ 45 and 45 does not work... $\endgroup$
    – lemon
    Nov 10 '21 at 18:09

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