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Drivers are lost upon converting a collection instance to a local set of objects
Open, Needs Triage by DeveloperPublic

Description

System Information
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 436.48

Blender Version
Broken: version: 2.81 (sub 13), branch: master, commit date: 2019-10-03 14:29, hash: rB8c991bf63a88
Worked: (optional)

Short description of error
Driving an object setting from its own custom property can be easy with a driver expression, for example setting a rotation control to: radians(self["prop"]*360)

Duplicating the object will produce a copy that also has the same internal driver expression independent of the original. However, if you instead put the object in a collection and then add an instance of the collection you have no access to any custom properties, which is its own bug that I'll report separately. So you go to Object->Apply->Make Instances Real to convert the collection instance to a local copy. This step removes the drivers.

Exact steps for others to reproduce the error

  1. Add a custom property to the default cube. Leave it as the default 'prop' property.
  2. Add a driver to the x rotation transform using the expression: radians(self["prop"]*360)
  3. Be sure to check the 'use self' checkbox below the python expression box.
  4. Put the cube object inside a collection.
  5. Add an instance of that new collection to the scene.
  6. Notice that there's no access to any custom properties now that the cube is in a collection instance, which is also a bug.
  7. Object->Apply->Make Instances Real, which converts the collection instance to its base objects
  8. The driver is gone.

Details

Type
Bug

Event Timeline

Hi, thanksfor the report.
Note: This was happening already with groups in 2.79:

(open the file and convert the right-most cube to real)

I believe this may be by design-ish. The conversion from instance to real in a way bakes the current transformations into the new object.
@Sybren A. Stüvel (sybren) is this something the animation module is interesting on looking at? If not feel free to close the report

  1. Notice that there's no access to any custom properties now that the cube is in a collection instance, which is also a bug.

Please report different bugs separately. And as far as I can tell this is not a bug.