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problem saving/loading driver on shader node
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System Information
Operating system: Linux-4.13.10-041310-generic-x86_64-with-debian-stretch-sid 64 Bits
Graphics card: GeForce GTX 1050/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 390.67

Blender Version
Broken: version: 2.81 (sub 3), branch: master, commit date: 2019-08-20 22:35, hash: rBdaba3e871ff5

Short description of error
Adding a driver from one value of a shader node to another, works great using the new Copy As New Driver tool. But saving and loading the file again will invalidate the driver and the input variable's Prop will be empty.

video demo

Exact steps for others to reproduce the error

  • load problem_saving_or_loading_driver_on_shader_node.blend
  • set up a driver linking two properties using Copy As New Driver
  • confirm its working
  • save and load the file
  • the driver is no longer working, as shown in problem_saving_or_loading_driver_on_shader_node_driven.blend

Event Timeline

MACHIN3 (MACHIN3) updated the task description. (Show Details)
MACHIN3 (MACHIN3) updated the task description. (Show Details)
Philipp Oeser (lichtwerk) lowered the priority of this task from 90 to 50.Aug 21 2019, 3:23 PM

I recall other issues with data paths in Shader Nodetree .
@Alexander Gavrilov (angavrilov) : havent checked code, but this was a bit special, right?

This is probably caused by the node tree being not a real datablock - the reference to the tree in the driver is destroyed on save & load, and you can't even select the correct reference from the dropdown list if you try creating it manually.

Alexander Gavrilov (angavrilov) changed the task status from Resolved to Unknown Status.Aug 23 2019, 4:32 PM

Reopening while we decide on the ideal way to fix this.