Drivers applied to modifier values don't get deleted when the modifier is applied or deleted #64170

New Issue

Brendan Lourenco · 2019-05-05T14:20:29+02:00

Brendan Lourenco commented

2019-05-05 14:20:29 +02:00

System Information
Operating system: Mac OS

Blender Version
Broken: 2.80, 1c58604070, master, 2019-05-05

Short description of error
When using a driver to drive a modifier value, deleting the modifier or applying it doesn't delete the driver.
So issues start occurring after this when you add the same modifier to the object and it automatically has this driver.
Or you duplicate the object and the driver is also duplicated, which means adding the same modifier to the duplicate also automatically has a driver.
This also leads to an issue with appending objects to other blend files. Since, when the driver is driven by other objects, appending this object will also append the objects the driver is linked to. Causing many more objects to be appended, without any real idea of how they are linked since the modifier that connects them was deleted.

Exact steps for others to reproduce the error
ModifiersAndDriversBug.blend
Grab the empty and move it, it should drive the thickness value of the solidify modifier.
Delete the solidify modifier on the plane.
Grab the empty again and move it (the plane shouldn't change, which is expected).
Duplicate this plane.
Add a solidify modifier back to the duplicated plane (it's thickness value will automatically have a driver attached).
Grab the empty again and move it (Nothing should happen as the drivers dependencies need to be updated for it to work).
Update the driver dependencies (It should work like before).
Delete the duplicate and save the file.
Open a new blender file and append the plane object from the saved file (the empty will also be appended, as it is linked to the driver).

**System Information** Operating system: Mac OS **Blender Version** Broken: 2.80, 1c5860407068, master, 2019-05-05 **Short description of error** When using a driver to drive a modifier value, deleting the modifier or applying it doesn't delete the driver. So issues start occurring after this when you add the same modifier to the object and it automatically has this driver. Or you duplicate the object and the driver is also duplicated, which means adding the same modifier to the duplicate also automatically has a driver. This also leads to an issue with appending objects to other blend files. Since, when the driver is driven by other objects, appending this object will also append the objects the driver is linked to. Causing many more objects to be appended, without any real idea of how they are linked since the modifier that connects them was deleted. **Exact steps for others to reproduce the error** [ModifiersAndDriversBug.blend](https://archive.blender.org/developer/F7007443/ModifiersAndDriversBug.blend) Grab the empty and move it, it should drive the thickness value of the solidify modifier. Delete the solidify modifier on the plane. Grab the empty again and move it (the plane shouldn't change, which is expected). Duplicate this plane. Add a solidify modifier back to the duplicated plane (it's thickness value will automatically have a driver attached). Grab the empty again and move it (Nothing should happen as the drivers dependencies need to be updated for it to work). Update the driver dependencies (It should work like before). Delete the duplicate and save the file. Open a new blender file and append the plane object from the saved file (the empty will also be appended, as it is linked to the driver).

Brendan Lourenco commented

2019-05-05 14:20:29 +02:00

Added subscriber: @Cradmon

blender-admin commented

2019-05-05 14:20:29 +02:00

#64397 was marked as duplicate of this issue

Sebastian Parborg commented

2019-05-06 18:37:59 +02:00

Added subscribers: @angavrilov, @ZedDB

Alexander Gavrilov was assigned by Sebastian Parborg

2019-05-06 18:37:59 +02:00

Sebastian Parborg commented

2019-05-06 18:37:59 +02:00

@angavrilov feel free to reassign if this in not for you.

Alexander Gavrilov commented

2019-05-11 15:21:08 +02:00

Added subscriber: @MACHIN3

Alexander Gavrilov commented

2019-05-11 15:26:10 +02:00

I'm pretty sure no drivers are ever removed just because you delete something they drive - the only exception being objects themselves, because drivers are attached to objects and disappear with the owner automatically. Thus this might be entering the domain of feature requests.

Brendan Lourenco commented

2019-05-11 20:55:42 +02:00

@angavrilov I'm guessing this driver behaviour (where the driver is attached to the object) was used as drivers can't be attached to modifiers. This works as expected, until you wish to apply or delete the modifier, as the driver will remain around since it is attached to the object. Which means manually deleting drivers, or potentially getting bug like behaviour through these leftover drivers.

The most obvious way I can see of solving this (with my minimal knowledge of blenders' codebase) is to attach drivers to modifiers, but that may mean making modifiers similar to how blender uses materials/particle systems. Which would be a feature request.

@angavrilov I'm guessing this driver behaviour (where the driver is attached to the object) was used as drivers can't be attached to modifiers. This works as expected, until you wish to apply or delete the modifier, as the driver will remain around since it is attached to the object. Which means manually deleting drivers, or potentially getting bug like behaviour through these leftover drivers. The most obvious way I can see of solving this (with my minimal knowledge of blenders' codebase) is to attach drivers to modifiers, but that may mean making modifiers similar to how blender uses materials/particle systems. Which would be a feature request.

Alexander Gavrilov commented

2019-05-12 00:58:10 +02:00

Drivers are stored in the same place as NLA tracks and other animation data. They are basically special animation curves that use custom input instead of current frame for the horizontal axis - you can even actually use that curve to tune the driver result.

Brendan Lourenco commented

2019-05-12 22:53:33 +02:00

Having heard that drivers are similar to keyframing, I tested keyframing, and it has the same issue as drivers.

Since reviewing my issue, I'd say this is probably not a bug but more of a user experience frustration. Since you have to remember to delete drivers manually if they are attached to a modifier you wish to apply or delete. If these drivers do not get deleted, they can cause bug like behaviour (which is why I initially thought it was a bug).

Having heard that drivers are similar to keyframing, I tested keyframing, and it has the same issue as drivers. Since reviewing my issue, I'd say this is probably not a bug but more of a user experience frustration. Since you have to remember to delete drivers manually if they are attached to a modifier you wish to apply or delete. If these drivers do not get deleted, they can cause bug like behaviour (which is why I initially thought it was a bug).

Alexander Gavrilov was unassigned by Dalai Felinto

2019-12-23 16:34:32 +01:00

Philipp Oeser commented

2022-05-28 12:25:20 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2022-05-28 12:25:20 +02:00

See also #89679 (Animation channels do not get removed from action when according modifier/constraint is deleted) which was not considered a bug, not even a Know Issue, will merge reports.

Philipp Oeser commented

2022-05-28 12:25:26 +02:00

Closed as duplicate of #89679

Philipp Oeser closed this issue

2022-05-28 12:25:26 +02:00

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Drivers applied to modifier values don't get deleted when the modifier is applied or deleted #64170