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How can I get the knife tool to snap to the same spot on another edge to get a straight cut. Here is an example of what I want to do:

enter image description here

When the line turns green the cut is straight. How can I do this in blender? I have tried using the magnet snapping tool but could not get it to work.

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  • $\begingroup$ I think the closest you can get now is use midpoint snap (Ctrl) to snap both ends of the cut to the middle of the existing edges, then using edge slide (GG) to slide the edge over. Not very optimal, I agree.. $\endgroup$
    – gandalf3
    Commented Apr 28, 2014 at 0:00
  • $\begingroup$ As the cut is made relative to the camera i have found that using orthographic view is the quickest way to achieve the result but i agree that a sketchup style, allign cut to axis shortcut would be cool! $\endgroup$
    – Daniel Bayley
    Commented Nov 3, 2017 at 2:26

2 Answers 2

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Press A while in knife mode to enable Angle Constrain.

Note that it snaps to angles relative to the view. For cuts on faces which are not aligned to any axis, you can:

  1. Press ShiftNumpad 7 to align the view to the face

  2. Press K to enter knife mode, then A to enable Angle Constrain:

    enter image description here

More information on Angle Constrain can be found in the Blender Reference Manual

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    $\begingroup$ additionall "Z". keys K, Z, C to cut though the entire (selected?) mesh, not just the face selected with the knife tool (blender.stackexchange.com/a/7156/3038) $\endgroup$
    – ThorSummoner
    Commented May 7, 2018 at 3:18
  • $\begingroup$ Seems like they should have the option to constrain angles relative to the geometry, since I imagine people rarely want to define their angles relative to the view $\endgroup$
    – Kyle Delaney
    Commented Jun 15, 2019 at 23:32
  • $\begingroup$ Please note that you have to start cutting first, and THEN you press C. Else something strange happens. $\endgroup$
    – tmighty
    Commented Jul 17, 2019 at 21:18
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Angle Constrain

You can use C while using the Knife Tool to enable Angle Constrain. This will enable you to cut at the following angles (with reference to your current view):

  • Vertically

  • Horizontally

  • At 45° angles

Also, notice that when you start to use the Knife tool, the 3D View Header bar changes to show you all the available Hotkeys to perform all possible actions with the Knife:

enter image description here

  • LMB: Define cut lines

  • RETURN/SPACEBAR: Confirm

  • ESC/RMB: Cancel

  • E: New Cut

  • CTRL: Toggle Midpoint Snap

  • SHIFT: Toggle Ignore Snap

  • C: Toggle Angle Constrain

  • Z: Toggle Cut Through

(NOTE: It is common in Blender to have available Hotkeys shown in the 3D View Header bar while using a tool, so check there while using other tools too.)

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    $\begingroup$ Is there a way to snap the cuts to grid? $\endgroup$
    – Alenanno
    Commented Jun 27, 2014 at 20:59

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