Possible bug with knife project?

Seem like there is a bug with knife project. I’m going to log it but thought I’d check here in case I’m doing something crazy. Projecting text onto a sphere works fine:

But on a more complicate mesh (this was imported from an STL file) - it just makes some of the cuts, and some also some cuts on the back faces:

I know what you are thinking - but the normals are all fine. I also recalculated them, and removed doubles. The mesh looks okay although there may be something weird as it was imported. Anyone got any ideas?

Here is the blend file:

knife.blend (626 KB)

Edit: This is with blender 2.68 official, and also in the nightly build.

It would help to have a version of this saved before you did the knife project so that we can try doing things with it ourselves. But I can tell you now that you haven’t applied the scale and rotation on your objects, and I’d be willing to bet that’s contributing to the problem.

Thank you!! Yes, that is much better with scale and rotation applied. Presumably still a bug though, that knife project has unpredictable behaviour without warning on scaled objects?

Also - although it is 90% better - there are still one or two cuts missing:

But that basically does what I need - thanks again :slight_smile:

Unapplied scales are not a good idea during modeling, texturing, or rigging. Scaling in object mode is meant as an option to be used during animation. If you’re making major structural changes, Blender needs to know what the model’s “real” size is. It’s not a bug so much as incorrect use of a feature.

About the project knife missing some cuts, it’s very likely related to the regular knife own bugs too, as it can misses cuts and as the Project Knife seems to share the same code it’s affected by the same problems too.

Fortunately, Howardt is working on fixing those knife bug, he recently fixed some of them in revision 59665 and 59767 (at the time i write, there’s no yet windows build including those revisions available on buildbot, maybe tomorrow) , so i imagine his fixes will then report on to the Project Knife too .

Personally I’d like to see a warning (like applying a modifier not at the bottom) if it doesn’t make sense or can be unpredicatable to do a knife cut on an object with scale (especially as it’s so easy to do for a noob). Anyway, thanks both of you.