Hi. Lately i have some annoying problem with knife tool (K key). After placing a cut and pressing enter, some random vertices from my modeled character are moved outside a mesh. For example i spent half an hour cutting my character’s collar to create additional geometry, then after seeing final work i discovered his face to be completely destroyed during the process, by some of vertices being moved outside his face to its front. I know it wasn’t my accidental fault, as i caught it in the act again few moments later.
How can i get rid of that bug? Or at least how can i prevent part of a mesh from accidental edits like those?
i dont think its a bug, i think its you not respecting the limitations of the tools and knowing when to use what.
could you do a quick video or screenshot showing the issue, and how you got there? i cant really tell what ur struggeling with. but it sounds like you are using the wrong tools.
show us what you have, and explain what you want, and i can tell you what tools you can use.
Ok. What else could it be then?
send an OBJ of the model. also, is this the only area why its happening?
i still dont think its a bug, let me have a quick look.
also before you export, please add a sphere at the location of the “bug” so i can more easily find it.
also i think u might wanna check out the Join tool by pressing J.
though this might solve it, id still like to diagnose your problem.
submit the blend file, not an OBJ as i suggested at first.
but id still love to get the sphere in the location shown in the video so i can easily find it.
Here it is. Do like in the video.
It seems it can be random. Sometimes when i’m undoing, problem isn’t occurring again. Also it wasn’t happening with this vertice only.
Attachments
bug knife.blend (544 KB)
Here is your blend file with those places cut with the knife tool http://pasteall.org/blend/index.php?id=43527
When working with knife tool make sure that you don’t have doubles vertices close to each other.
Second advice is that since Blender wasn’t ngon tool at start and knife tool is older than Ngon try to remove ngon at earlier stage to avoid unpleasant surprise down the road.
Long time ago i have reported some kind of similar bug with this tool, knife tool have some kind of problem when working such small place.
So what i have done:
- remove doubles first
-remove big ngons i cut with the knife and - give myself some space to cut at the place you were cutting.
Here is short youtube video to show you how i did it 
https://youtu.be/Ae_Fk_uqtUA
Thank you. I was thinking that doubles may cause those anomalies too.
I’m a bit new in blender, but i know that close spaces are sometimes necessary. At least in that mesh. With subdivision surface modifier they whet edges, what was quite desired by me in those places.
You give space first then you cut and then you slice them back into places 