I used the spin operator to duplicate a circle, after that I tried to knife project all circles (single object), all the duplicated circles don't have an effect but the original circle is cut out. Why is that?

enter image description here

.blend file

It's a bug

  • $\begingroup$ The knife project tool does odd things like that, I know. I haven't figured it out either yet. $\endgroup$ Mar 25, 2014 at 20:46
  • $\begingroup$ I know that cutting holes into mesh in general is a problem. What happens if you place the circles slightly over the so that it is not actually a hole? $\endgroup$
    – Vader
    Mar 25, 2014 at 20:49
  • $\begingroup$ @Vader it seems that knife project needs intersecting edges to cut properly. $\endgroup$
    – stacker
    Mar 25, 2014 at 21:55
  • $\begingroup$ Stacker, I'm having a discussion about this issue now on BlenderArtist.org $\endgroup$ Mar 25, 2014 at 23:20
  • 1
    $\begingroup$ It'd be nice to see "it's a bug" as the accepted answer. $\endgroup$
    – Matt
    Mar 26, 2014 at 16:24

1 Answer 1


I got it to work by subdividing the target object a lot:

enter image description here

When the target was not subdivided, not all of the knife circles would cut, but once I subdivided, they all cut. I have no idea why though.

However, trying to get it to work on a cylinder is more difficult. The way I got around it was:

  1. Add a circle mesh and set the Fill type to Triangle Fan:

    enter image description here

  2. Then when you do the knife projection, all the circles will cut:

    enter image description here

  3. Then you can extrude the cut circle into your cylinder


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