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I'm trying to use the knife tool. I click on the tool and it does appear.

But when I try to press LMB to cut, instead of the guidelines I am supposed to create appearing, the only thing that happens is that only the green square that marks the beginning appears, and it always appears at the source point of the object. (you can see in the gif I added that i'm trying to click and nothing happens)

In addition, from time to time it happens that the tool does respond to my clicks. (It should be noted that sometimes it reacts and sometimes not. In both cases it happens for no apparent reason) But even when the tool responds, it seems that for some reason it constantly insists on choosing the edges of the objects instead of creating edges the way I draw with the mouse.

I tried of course to check if it had anything to do with the edge selection mode, but no matter what mode I was in or what object I tried to perform the action on, All I could do was make this green square appear and nothing more.

I believe this is some definition that has changed in this specific project, because in every other project the knife works properly.

please help!!

enter image description here

JonasBH2
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  • What Blender version are you using? – Emir May 31 '21 at 15:40
  • you can share the blend file via https://blend-exchange.com/ so that it's easier for other to look into your issue. – Nand 27 May 31 '21 at 17:07
  • for Emir: im using blender 2.91 – JonasBH2 May 31 '21 at 17:11
  • for Nand 27: it doesn't let me upload files more then 30mb – JonasBH2 May 31 '21 at 17:14
  • @JonasBH2 a standard procedure when reporting bugs or asking for help is reproducing the problem in as simple environment as possible. Creating a new project and reproducing the problem is sometimes hard, but removing half of the objects, checking if the problem remains and repeating that until there's a minimum number of objects still reproducing the issue, not only makes it easier to share the file, but also to find the problem. – Markus von Broady May 31 '21 at 17:45
  • so i just tried the solution that Nand 27 offered. i opened a new project, and the knife tool worked fine.

    the second i tried to copy one of the objects from the problematic project, the knife started again with the same problem, and it behaves the same way with new objects I create in the new project.

    you can see i shared the project in the link above

     – JonasBH2 May 31 '21 at 18:03
  • Does this answer your question? Knife Tool is stuck to the origin of the geometry of the object Applying the Robin Bett's answer solved the issue for me (on your file supplied) – Markus von Broady May 31 '21 at 18:24
  • finally! yes, the link you gave me contained exactly the question with the right solution. Thank you so much!! how can i mark your answer as the right answer? – JonasBH2 May 31 '21 at 18:32
  • @JonasBH2 Upvote Robin Betts. :) – Markus von Broady May 31 '21 at 18:35

1 Answers1

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This issue occurs when you have overlapping geometry like double faces. try selecting all in vertex mode and hit m> merge by distance. this might be the solution for your issue!

Nand 27
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  • ok! I can see the overlapped face in you screen. You can spot this when a face looks weird (something like weird shining). You can see it in the first selected face when you rotate the screen in the clip you shared. – Nand 27 May 31 '21 at 16:46
  • I assume when u siad to "select all" you meant that I would select an object, then select all of its vertexes in edit mode with vertexes selection mode.

    i tried. nothing changed.

    Besides, the solution you suggested sounded more appropriate to me if the problem was with a particular object.

    In my case, the knife tool behaves this way about all the objects in the project, including new objects I create

     – JonasBH2 May 31 '21 at 16:53
  • by the way, about what u said that u thought it was overlapped face, it was a seleted face – JonasBH2 May 31 '21 at 17:00
  • sorry! it looked like a overlapped face, maybe due to the compression. if you don't find the solution it's best to copy all the objects to a new blend file. – Nand 27 May 31 '21 at 17:03
  • It indeed looks like z-fighting when it moves, but looking on a paused frame reveals it's GIF dithering, not z-fighting: https://i.imgur.com/xB8XswE.png – Markus von Broady May 31 '21 at 17:52