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problem with Project Knife and ngons
Closed, InvalidPublic

Description

System Information
Operating system and graphics card
winxp sp3

Blender Version
Broken: blender-2.70-c359de2-win32
Worked: never worked

Short description of error
Project Knife on a ngon face can result in very unpredictable/buggy result

Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps

  • load the attached blend

  • on the 3D view, you have already prepared 2 big circles that are filled with a ngon, on top of both circles, there are 6 small circles to be projected by the knife project.
  • if you do a knife project for the big circle on the left and the 6 little ones (in a circular pattern), it will fail
  • if you do a knife project for the other big circle on the right and the 6 little ones (in an aligned pattern), it will work

as shown in screenshot :
http://i.imgur.com/1Kona2o.jpg

Problem noticed in that Blenderartist thread for more information :
http://blenderartists.org/forum/showthread.php?331554-Why-does-knife-project-not-cut-properly-if-target-mesh-is-not-subdivided

Details

Type
Bug

Event Timeline

Sanc Tuary (sanctuary) set Type to Bug.
Sanc Tuary (sanctuary) created this task.
Sanc Tuary (sanctuary) raised the priority of this task from to Needs Triage by Developer.
Bastien Montagne (mont29) triaged this task as Confirmed, Medium priority.Mar 26 2014, 7:43 PM

The radial pattern doesn't cut as long as there're 2 overlapping circles in the projector mesh!

As there's a duplicated circle (the one that cuts), the operator doesn't behave well except for it

Removing the duplicate fixes that!

  • Select a circle's edge and click L (select linked) and delete

(attached a pic for the duplicated circle)

The question now, what should be the default behavior when we have 2 overlapping meshes to be projected on another mesh?

Well spotted !
I completely forgot that a 360 spin duplicate will always lead into doubled result on the original mesh and required a w -> remove double

Closing, while knife project could do a remove doubles, I think its better we expect correct non overlapping projection lines.