I am trying to cut two different meshes A and B with the same polyline P so that I can join A and B afterwards with no holes or anomalies. I am using the knife project tool and this works quite well.

The problem: the knife project seems to have vertex snapping enabled. Whenever P is too close to any vertex of A or B the new inserted vertex snaps to those vertices. However, the vertices of A and B do not lie at the same positions. Thus, it often happens that-using the same polyline for the projection-the A and B do not fit perfectly due to holes in the joint mesh.

Is there any (hidden) parameter or other possibility to disable this snapping behavior in the knife projection? Otherwise, I need to implement the same functionality by myself just because of the snapping... and I do not want to do that :-D

Edit: it seems there is not only a vertex snapping but a general inaccuracy. I tried to illustrate the problem with the following images.

The polyline (vertices in orange) and one of the meshs: enter image description here

After applying the knife project tool (polyline in orange): enter image description here

Hiding the polyline: enter image description here

  • $\begingroup$ I'm having some difficulty reproducing this .. can you share an example file on pasteall.org/blend ? Possibilities.. projection, automerge.. floating-point error... or I'm wrong.. $\endgroup$ Jul 21 '21 at 11:19
  • $\begingroup$ I am going to share an example in a minute. But... is the accuracy of the knife project tool depending on the current zoom level? I got different results when calling the tool in different zoom levels... $\endgroup$ Jul 22 '21 at 8:34
  • $\begingroup$ Could be.. floating point? .. Stupid question, but have to ask, sorry .. you are in an orthographic view? $\endgroup$ Jul 22 '21 at 8:41
  • $\begingroup$ Yes, I'm in orthographic top view. I already thought about the floating point problem since you mentioned it in your previous comment. However, if I zoom in until the background grid is in cm then the knife projection is pretty accurate. So, I guess, the zoom dependency is built-in... $\endgroup$ Jul 22 '21 at 8:47
  • $\begingroup$ Clipping range? Although.. Camera Z should be chucked out, and have nothing to do with it, really. $\endgroup$ Jul 22 '21 at 8:52

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