I'm trying to use Knife Project to cut a shape in a cylinder. For now I'm testing on the cube. I've used this answer as a guide. I added the mesh cube, then added a curve circle. I grabbed the circle and moved it up the Z axis until it was above the cube, then I scaled it so it was smaller than the cube. It's now above the cube. I hit numpad-7 to set the view. Then I select the circle, and use shift to also select the cube. I hit tab to go into the Edit Mode and then go to Mesh->Knife Project. I've tried variations on this, but it NEVER cuts through even one face of the cube. I've tilted it to a different angle for this screenshot, but it shows what I'm getting. It outlines the shape of the circle I'm using as a knife tool, but it never cuts it out. enter image description here I can press 'G' and then move the circles it makes around, or extrude them, but it never cuts through the cube, like in the answer I've linked to. I've tried using the knife tool, but that doesn't work. (Also, both the knife tool and Knife Project are only in Edit Mode, and the answer does not specify to change to the Edit Mode.) I've tried selecting the cube, going to Edit Mode and selecting the circle with ctrl-lmb. I've done the same with selecting the circle first, then selecting the cube the same way.

I've also tried, after using Knife Project and getting the circles on the cube faces to use the delete command, but none of the options delete just the circles from the cube faces. (I do have Cut Through checked on the panel that comes up for Knife Project.)

What do I need to do to make the Knife Project cut through the faces?

(Note: I've also looked over this question and the one answer to it, but I haven't found anything to tell me what I'm doing wrong or why I can't cut through the faces.)

  • $\begingroup$ The answers you found are more than 4 and 7 years old, Blender changed a lot since then. I've never used the Knife Project tool much in the past, maybe they changed how it works. What do you want to achieve, to you want to have a hole where you cut the mesh or do you want the new face(s) to be separated from the rest of the mesh? After Knife Project, the new face(s) will be automatically selected, so to get a hole delete directly after cutting: press X > Delete> Faces. If you just want the new face(s) disconnected from the rest, simply press Y. $\endgroup$ Jan 17, 2022 at 10:17
  • $\begingroup$ Both of the links relate to a very old version of Blender. You don't say what version you're using but try this quick tutorial for the later versions. You should get a dialog in the bottom left of the screen after you've done the cut which has a 'Cut through' checkbox on it. $\endgroup$
    – John Eason
    Jan 17, 2022 at 10:20
  • $\begingroup$ @JohnEason He has the Cut Through option clearly visible enabled in the screenshot. There is a misunderstanding on his behalf: I guess he thinks "cut through" means splitting the new edge in two separate edges so that the cut section is separated from the original mesh. And he's using 2.92.0, also visible in the screenshot. $\endgroup$ Jan 17, 2022 at 10:22
  • $\begingroup$ @Gordon Brinkmann So he does! I guess I'm not fully awake yet! :^) $\endgroup$
    – John Eason
    Jan 17, 2022 at 10:24
  • 3
    $\begingroup$ @Gordon Brinkmann I'm 76 next month and don't get up very early nowadays so cut me some slack! :^) $\endgroup$
    – John Eason
    Jan 17, 2022 at 10:34


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