enter image description here

In the pic attached I'm trying to make a perfect diagonal edge across the face as I've so beautifully illustrated in MS paint. I've tried subdividing and moving the vertices along the edge so that they look close enough, but 1) they aren't the exact distance and 2) I have to create the vertices on the opposite diagonal side which is a pain.

And I have tried using the ruler/protractor tool but that's been fairly useless so far because 1) it disappears when I go back into edit mode so I can't place my vertices exactly where it was, and 2) you can't enter exact values in it, so when you get down to a measurement like 3.4000005cm you'll never be able to match it on the other side (if that makes sense).

Any suggestions to go bout this? Theres probably some stupid easy solution to it but I've been at this for HOURS and still can't figure it out.


One way to get diagonal based lines like that is to use Offset Edge Slide which will add loopcuts on both sides of the present edge. However one edge is needed, so select opposite vertices and press J to join them with the edge and split the face.

Then select the edge, open Toolshelf (or press Ctrl+Shift+R) and drag the mouse for the effect.

enter image description here

Regarding the edge you create for this tool to work.
You can dissolve it afterwards but note that it creates quite horrible Ngon in the middle which is better to avoid. It all depends on the purpose of the model but it's best to stay away from this geometry to avoid any problems later on.

  • $\begingroup$ This was the easiest solution, I hate that I didn't just ask this question earlier and save all those hours of confusion. Thanks for the help. $\endgroup$ – LuckyCOINNNN Jul 24 '18 at 21:26
  • $\begingroup$ Personally, I think this is the best answer ... it gives the extra 'Even' option, to equalize the offset down the edges from the corners, if that's the kind of 'perfect' you are looking for. $\endgroup$ – Robin Betts Jul 24 '18 at 22:21

All in Edit Vertex mode:

  1. Select diagonally opposite vertices, and make a diagonal edge (J)
  2. Bevel (CtrlB) the (already selected) diagonal edge: in the tool region, set Type to say, 'Width', Segments to 2, and Profile to 1.
  3. F Combine the (already selected) two faces on the diagonal band.
  • $\begingroup$ This works equally fine as the other answer. Thanks so much. $\endgroup$ – LuckyCOINNNN Jul 24 '18 at 21:28

A possible option is the knife project tool. You can access it in edit mode at the Tool Shelf ‣ Tools ‣ Mesh Tools ‣ Add: Knife Project.

  1. Create a second Plane and scale it to the correct with.

  2. Point it to an edge with the Track To Constraint: Shift the origin of another object to the edge. RMB RMB select the cutting plane, ⇧ ShiftRMB RMB select the other object and press ⎈ CtrlT > Track To.
    enter image description here

  3. RMB RMB select the cutting plane and ⇧ ShiftLMB LMB select the plane object. Go to edit mode ↹ Tab, then choose Knife Project.
    enter image description here
  • $\begingroup$ Thanks for your response, but when I press Ctrl/T and track to, I get this result. I have my plane and cube (rectangle) as separate objects and am in object mode. postimg.cc/image/mcilje7cb $\endgroup$ – LuckyCOINNNN Jul 24 '18 at 20:24
  • $\begingroup$ A rectangle (mentioned in the question) is a planar object unlike a cube. Make sure the origin of cube and the plane are on the same threedimensional plane (e.g. XY). Also, read the documentation on the track to constraint $\endgroup$ – Leander Jul 24 '18 at 20:27
  • $\begingroup$ Sorry I read the page, but I'm just not clear on what you mean by make sure they're on the same 3D plane. $\endgroup$ – LuckyCOINNNN Jul 24 '18 at 20:52
  • $\begingroup$ I figured it out, I just needed to go to the constraints tab and change it to the Z axis. postimg.cc/image/ud1hlpdor $\endgroup$ – LuckyCOINNNN Jul 24 '18 at 21:20

If what you want is just a diagonal edge you can easily achieve that with the Knife Tool:

1) Initial setup:

first go to edit mode in vertex select like the picture below and press K; you'll notice your mouse cursor has changed shape and is now a little knife

enter image description here

2) Use the Knife Tool:

after pressing K position your cursor in one of the vertex you want the diagonal edge, you'll notice a green dot appears when the cursor snaps to one vertex, now Left Click and drag to the opposite vertex (you'll see a red dot in here when the cursor snaps to this vertex), you'll notice a purple line is being created, then Left Click again on the opposite vertex and press Enter and now you have a diagonal edge (like image number 3)

enter image description here

3) Final result and tips:

  • if you press C while the Knife tool is selected you can cut your mesh following a 45 degrees increment, very useful in Ortho Front, Top ,Side views since it allows you to cut along the axis
  • if you press E you can start a new cut without confirming the previous one, very useful if you have multiple cuts and you want to cut everything first and confirming later (doing one cut and confirm and then doing another cut and confirming and so on is very time consuming)
  • if at any point you don't like your cut and don't want to confirm it simply press Esc or Right Click

enter image description here

  • $\begingroup$ What I am trying to do is get 2 diagonal edges along the horizontal and vertical edges like in the image posted, I am not trying to connect the vertices $\endgroup$ – LuckyCOINNNN Jul 24 '18 at 20:26
  • $\begingroup$ yeah I figure that out later, try with knife project tool as the other user said :) $\endgroup$ – Nobinberg Jul 24 '18 at 20:29

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