Ease drivers don't migrate to new Bendy Bones (datapath change, backwards-compatibility broken) #49288

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Adrian Winchell · 2016-09-07T23:25:50+02:00

Adrian Winchell commented

2016-09-07 23:25:50 +02:00

System Information
Windows 10, GeForce GTX 960

Blender Version
Broken: 2.78RC 0e5089c
Worked: 2.77a abf6f08

Drivers assigned to bone eases in the previous release disappear when opened in the release candidate (2.78RC)
Example:

Create a 3-segment bone in 2.77a, and in pose mode, assign a simple driver to the ease out. (my example: "#1.5" typed into the field)
Save and open in 2.78RC

The bone has the value last assigned to it by the driver, but the driver itself has vanished.

I'm guessing this is due to the datapath change of this property in the new version:
2.77a: bpy.data.armatures["Armature"].bones["Bone"].bbone_out
2.78RC: bpy.data.objects["Armature"].pose.bones["Bone"].bone.bbone_out

The driver reappears even if the file is saved in 2.78RC, then reopened in 2.77a, suggesting it isn't removed from the file, just no longer interpreted by the program. In fact, it appears in the graph editor for drivers in both versions, and if a new driver is added to the ease in 2.78RC, both drivers will appear in the graph editor even though only one is affecting anything.

Here is a sample file with the above-mentioned driver saved to the bone only in 2.77a:
http://pasteall.org/blend/index.php?id=43433

**System Information** Windows 10, GeForce GTX 960 **Blender Version** Broken: 2.78RC 0e5089c Worked: 2.77a abf6f08 Drivers assigned to bone eases in the previous release disappear when opened in the release candidate (2.78RC) Example: - Create a 3-segment bone in 2.77a, and in pose mode, assign a simple driver to the ease out. (my example: "#1.5" typed into the field) - Save and open in 2.78RC # The bone has the value last assigned to it by the driver, but the driver itself has vanished. I'm guessing this is due to the datapath change of this property in the new version: 2.77a: bpy.data.armatures["Armature"].bones["Bone"].bbone_out 2.78RC: bpy.data.objects["Armature"].pose.bones["Bone"].bone.bbone_out The driver reappears even if the file is saved in 2.78RC, then reopened in 2.77a, suggesting it isn't removed from the file, just no longer interpreted by the program. In fact, it appears in the graph editor for drivers in both versions, and if a new driver is added to the ease in 2.78RC, *both* drivers will appear in the graph editor even though only one is affecting anything. Here is a sample file with the above-mentioned driver saved to the bone only in 2.77a: http://pasteall.org/blend/index.php?id=43433

Adrian Winchell commented

2016-09-07 23:25:51 +02:00

Changed status to: 'Open'

Adrian Winchell commented

2016-09-07 23:25:51 +02:00

Added subscriber: @snapai

Joshua Leung was assigned by Bastien Montagne

2016-09-08 09:31:55 +02:00

Joshua Leung commented

2017-03-06 13:06:11 +01:00

Changed status from 'Open' to: 'Archived'

Joshua Leung closed this issue

2017-03-06 13:06:11 +01:00

Joshua Leung commented

2017-03-06 13:06:11 +01:00

Technically, the old driver is still there, and should still work perfectly fine.

What has changed is that now, instead of accessing this property via the Armature datablock (i.e. armature -> bone -> property), we're now accessing it via the Object/Pose object (i.e. object -> pose -> posebone -> bone -> property). Fundamentally, it's still just accessing the very same property on the Bone struct.

This change was necessary / desireable as, if we kept it the old way, animators working with Bendy Bones would end up with the Ease In/Out properties getting keyed in a separate action attached to the Armature instead of the Object (where the rest of the character's animation is located). There are obvious downsides with that, hence the change.

So, IMO the resolution here is really that we just need to add a note in the release notes to this effect.

Technically, the old driver is still there, and should still work perfectly fine. What has changed is that now, instead of accessing this property via the Armature datablock (i.e. armature -> bone -> property), we're now accessing it via the Object/Pose object (i.e. object -> pose -> posebone -> bone -> property). Fundamentally, it's still just accessing the very same property on the Bone struct. This change was necessary / desireable as, if we kept it the old way, animators working with Bendy Bones would end up with the Ease In/Out properties getting keyed in a separate action attached to the Armature instead of the Object (where the rest of the character's animation is located). There are obvious downsides with that, hence the change. So, IMO the resolution here is really that we just need to add a note in the release notes to this effect.

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Ease drivers don't migrate to new Bendy Bones (datapath change, backwards-compatibility broken) #49288

The bone has the value last assigned to it by the driver, but the driver itself has vanished.