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Knife Project: does not use the correct, up to date, source mesh for the projection
Confirmed, NormalPublicBUG

Description

System Information
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: Quadro 600/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 369.09

Blender Version
Broken: version: 2.81 (sub 0), branch: master, commit date: 2019-07-31 18:01, hash: rB881675dff13d
Worked: (optional)

Short description of error
Knife project does not use the correct, up to date, source mesh for the projection. This happens if, while in edit mode, you decide to modify the source mesh before running the knife project operator. The knife project ends up using the original shape of the source mesh at the time that edit mode was entered.

Exact steps for others to reproduce the error
Blend:

  • Load attached .blend
    • Contains a cube and circle
    • Selection order is: circle then cube (trying to project circle onto cube)
  • Enter edit mode with both objects selected
  • Modify the circle's vertices to just change the shape so it's obviously not a circle
  • Select all verts of the modified circle
  • Shift-Select all verts of the cube
  • Run Mesh -> Knife Project
  • Observe that the project operation did not use the circle's current set of vertices, but rather used the original shape

Initial state:

After changing shape of circle then running project:

Event Timeline

I just reproduced this bug locally.

System Information
Operating system: Darwin-16.7.0-x86_64-i386-64bit 64 Bits
Graphics card: Intel(R) Iris(TM) Plus Graphics 640 Intel Inc. 4.1 INTEL-10.25.24

Blender Version
Broken: version: 2.81 (sub 3), branch: master, commit date: 2019-08-23 18:32, hash: rBf16a28c4afbf

If nobody is looking into it and a maintainer approves it, I can try fixing it.

Philipp Oeser (lichtwerk) renamed this task from Knife project does not use the correct, up to date, source mesh for the projection to Knife Project: does not use the correct, up to date, source mesh for the projection.Sep 3 2019, 12:35 PM
Philipp Oeser (lichtwerk) lowered the priority of this task from 90 to 50.
Germano Cavalcante (mano-wii) changed the subtype of this task from "Report" to "Bug".

It is interesting to note that if you add a modifier to the Circle, the projection on the other object is that of the original Circle plus the modifier.
This makes me suspect that the modifier is being computed for two objects instead of one.

@Sergey Sharybin (sergey), it probably has nothing to do with the bug, but is this double modifier computation expected?