Knife Project Not Working #90656

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 2060 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 471.68

Blender Version
Broken: version: 3.0.0 Alpha, branch: cycles-x, commit date: 2021-08-12 11:03, hash: blender/blender@425388bc0f
Worked: (newest version of Blender that worked as expected)

Short description of error

Confirmed in master also
knife project shows error "No other selected objects have wire or boundary edges to use for projection"

Exact steps for others to reproduce the error

Try knife project anything

Added subscriber: @Shady.Hamza

blender/blender#92842 was marked as duplicate of this issue

blender/blender#91512 was marked as duplicate of this issue

blender/blender#91130 was marked as duplicate of this issue

blender/blender#90716 was marked as duplicate of this issue

Added subscriber: @PratikPB2123

Thanks for the report. This happens after the commit blender/blender@49ea8e4fea made in master.

From Modeling module discussion I noted the steps to use knife project:

First select the object to be cut.
Switch to edit mode
Select an object from outliner ({key Ctrl LMB}) to use for projection
Mesh -> Knife Project

May be this report can be closed but will keep open for developers opinion.

I see, that worked thanks, so the old way where I select the cut Obj shift Select the Obj i wanna cut then enter edit mode, that doesn't work anymore huh

Added subscriber: @SteffenD

I can confirm that it works as described in the official workflow in 2.93 but doesn't work any more in 3.0 master

Added subscribers: @Vyach, @deadpin

This comment was removed by @Vyach

@Vyach , I agree that Sync selection has to be enabled.

Update in manual is expected to describe the new steps so adding #documentation tag.

Added subscriber: @mano-wii

In #90656#1207052, @Shady.Hamza wrote:
I see, that worked thanks, so the old way where I select the cut Obj shift Select the Obj i wanna cut then enter edit mode, that doesn't work anymore huh

This way it was working was not intentional.
It's even confusing to know which mesh will be cut when more than one mesh can be in edit mode at the same time.

In 2.79 this worked because only the active mesh was in edit mode.

Now you need to select the objects that are not in edit mode. For that you can use Ctrl + Select for example.

The manual, in fact, needs to be updated:
https://docs.blender.org/manual/en/3.0/modeling/meshes/editing/mesh/knife_project.html

Added subscriber: @lichtwerk

Changed status from 'Needs Triage' to: 'Archived'

Well, as a bug report, this can be closed (functionality works as intended and D12264: Knife Project:: update documentation is accepted).

Select an object from outliner (+) to use for projection

For that you can use Ctrl + Select for example.

Just noting that this works in the viewport (dont have to do this in the Outliner).

This issue was referenced by 8325

Added subscriber: @FloridaJo

Removed subscriber: @Vyach

Added subscriber: @NXSK

Added subscriber: @robcarrich

Added subscriber: @1D_Inc

This is happening because multiedit was implemented from homogeneous system without active object paradigm (like 3dsmax, Maya or AutoCAD) into hierarchical system with active object paradigm (to Blender)
As a result, the design faced systemic incompatibility, but instead localizing multiedit, which corrupts different functions and also messes up with instances, it was decided to redesign knife project in 3dsmax way.
The resulting design is quite unsuccessful.

To solve knife project issue it is needed to do the opposite - return knife project behaviour but limit multiedit to special submode, so

on pressing tab you enter regular active object edit mode
and then have the possibility to expand regular active object edit mode to multiedit with special hotkey if it is needed.
Such design will give a space and reconcile both homegemeous system like mutiedit and hierarchical system like knife project, so such behaviour will allow to bypass systemic incompatibility.

It will be more wise solution since multiedit is not supposed to be used very often anyway, the most time you edit just a single object at once, and sometimes, quite rarely, tweak several objects when it is needed - and only if selection doesnot contain instances (linked data objects), otherwise they will be immediately corrupted during multiedit session, which makes multiedit a double limited solution in general.

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Knife Project Not Working #90656