Blender development todo list -- Animation System #55365

New Issue

NOTE: this is a direct dump of https://wiki.blender.org/index.php/Dev:Source/Development/Todo/Animation (without cherrypicking the [still] valid items)

Armature

Separate ~~and Join~~ tools should move animdata around too (using BKE_animdata_separate_by_basepath), see report: #31966
B-bones (beziers) still use old code that keeps Z axis up, which causes twisting in cases. the solution as used for curve-deform could be copied here as well. #26090
B-bones handling of rotations sometimes is wrong (hard to fix, maybe same/related issue as the one above, see #39491, #41678).
Armature editmode undo/redo issue: since armature edits sync with Pose all the time, a delete/undo command will still not retrieve all bone group, constraint and driver infos in pose-bones. #28350
Skeleton Sketching does not correctly compute bone envelope sizes, resulting in near/effectively zero but non-zero size values. #34541
Flip Names removes Bone numbers #34282
Better handle of Pose transforms when applying Object-level transforms to data (#41699)?
The Dual Quaternions algorithm behind the "Preserve Volume" function (Armature Modifier) needs an update (#43188) - [http://rodolphe-vaillant.fr/?e=59 Paper]

Rigging

Copy Menu - the future of tools like this is currently unclear. Certainly for rigging though, they are often the only useful way to do mass changes.
Proxy Objects (armature, group): the system works, but has limits. It can only proxy once (not duplicates), motion paths don't draw for it either (#26256). The feature was added in 2007 but never further upgraded or improved.
Proxy Bones: there's no or incorrect syncing of bone transform limits. #32116
IK solver does not handle situations where you want only stretch when needed, would need to be implemented explicitly (report #32174)
Warning: if you use "Automatic weighting" (Laplacian "bone heat") you need to ensure the normals are correct, so don't use negative scaled models.
X-mirror for Armature editmode changes roll values on Transform, but with ESC it doesn't restore these rolls.
Setups with "Maintain Volume" modifier fail for some Bone rotations (work around included) #31975
Can't undo hiding the bone #38911
Bone '''Inherit Scale''' could be made to work with negative values #40506
Automatic Weights are slow on high-density meshes #53494

Constraints

Constraints involving rotations - in particular, childof, transform, copy rotation - with influence < 1 are known to behave weirdly due to limitations with the underlying math. In particular, matrix decomposition issues mean that rotations are only guaranteed to be clamped to lie with +/- 180 degrees (causing issues with gears and other setups where the magnitude+direction of rotation matters), and negative scale factors cannot actually be individually identified with any accuracy. These are well known limitations of the current system, which are non-trivial and currently intractable problems. (e.g. #40671, #37623, #40873, and many many others before them)
PyConstraints - these are quite high on the priority list to restore, but are still waiting on a few technical issues to be resolved still
Transform Constraint functions quite limited. Postponed to fix. #27286
Note: the "Child of" constraint functions best if the bone itself is not parented.
Bug report about "Child of" and "transform" constraints failing #29100
"Apply visual transform" fails with IK constraint. #27743
Mirror tool (Object mode) doesn't work for Child-of constraints always #32248
Pivot Constraint is broken currently, doesn't function at all. e.g. #32963
Copy Transforms constraint jumps when changing influence (especially when shear is involved) #34532
Maintain volume constraint behaves wrong ({{GitCommit|48079)
Parenting object with constraint causes tansform ({{GitCommit|45531)

Dependency Graph

The 2.5 spec "animate everything" works, but what's missing is a clean dependency solver to ensure anything you relate gets displayed in real time on changing properties or while posing/animating. Here we collect known issues to solve later.

Driver example #26734 #35863
B-Bone ease driver doesn't update well #28312
Constraint with vertex group target on subsurf mesh not working #29059
New dependency graph for all datablocks (Specially for all kind of material and texture datablocks, ie: Stucci parameters). #20956, #23426, blender/blender-addons#23639, #22698, #24562, #91015, custom props 3 #32495, custom props 4 blender/blender-addons#28286
Bones and the object dependency graph?
Drivers using object data (e.g. lamp distance) do not update on changes immediately (#27424)
Image Sequence Not Updating in 3D Viewport when it's properties are driven with a driver (#30514)
Wonderful complex dependency of Cloth with Duplication and NLA #29838
Dependency graph and layer switching error (#27032, #27032)
Group duplicators + deform, error related to drawing modes and layers. #24774
Object has modifier dependency on an object inside a linked group. #26724
Cloth sim inside a linked group updates badly (pointcache issue too). #27287
Object uses a constraint dependency to an object inside a linked group. #27694
Updates with custom properties very slow: #31647
Proxy: needs to be created with group-instance on location where it starts - to make pointcaches work. #32944
Multiple duplications of group, 1 proxy error: #31891
Two scenes, in two windows, with partial shared data - bad updating. #33560
Viewport dupligroup evaluated in original location, render dupligroup in dupli transformed location gives difference between viewport and render (#33591, #33595)
Instances linking to group that link to group with animated characters doesn't work. #34025
Dupligroup with Array modifier but control object not in group. Undefined result. #35562
Dupliframes on armature - armature cannot be posed once keyframes exist.#35929
Lack of refresh on layer visiblity change #37262
Changing texture doesn't refresh deform modifier #39717
Drivers using own transform channels are not reliable #50066

Animation System

Notes:

When constructing data paths, only use the "" form for strings. Even though Python supports both interchangably, we only use the "" form for strings used for names. Using the ' ' form instead may lead to unexpected evaluation results.
Properties for GLSL shaders are not animated during anim playback, they are compiled for speed.
Driver test cases (should be in regression): #24012
Opening 2.4x files with objects with shared Actions results in missing animations.
Unable to bake actions for multiple selected objects #38308

Todo:

Frame-mapping (map to, old) is still half implemented. Candidate to be removed?
~~Remove animation data from objects, when all their animation is deleted.~~
Non-relative vertex keys aren't really usable currently, see #22431
Animation 'overrides', or some kind of functionality to keep recently changed (but already keyframed) values from changing on scene updates would be nice to have, see #26019.
Support for passing string/pointer values into scripted expressions using Driver Variables as containers for this blender/blender-addons#26306
Animation playback: the way how the timer manages 'current frame' is not well implemented. Error for example happens when using redo-operator on playback. Needs revision.
Animating collections (like object layers): per-element curves might apply incorrect because of restrictions for overall collection, #29883
An easy way to clear Custom and rig UI Proprieties from the selected PoseBone, setting up the default values - like Alt+R for Rotation. Alt+C looks to be a good hotkey to clear Custom Proprieties from PoseBones
Mirroring Bone Pose working for Bone Custom Proprieties and Custom UI Proprieties
Duplicate objects could check all RNA paths, and fix ID names in it for new names. #31161 #36626
Changes such as selecting/renaming groups in anim editors don't affect bones. This was never meant to work, since "Group channels != Bone channels" (even though when dealing with bones, the default behavior is to group together bone fcurves to make them easier to find). Anyways, for usability, it would be nice to eventually get this sync working again. But, "Not-A-Bug-For-The-Tracker (TM)"!. Examples: #35798
NLA Strips need "cycle offset" for the case where a strip gets split in the middle of a repeat. However, cannot implement this without a thorough unit test set for this code #27503
NLA influence animation has to be done without EditMode on strips. Inside EditMode doesn't work yet (was meant for animating time).
Drivers duplication won't preserve targeted objects #39079
FCurve easing could use normal of handles #39916
Undo re-orders dope sheet items which have cyclic dependencies #38491.
Editing keyframes in Graph Editor currently does not force motion paths to get recalculated. #42181
"Separate" shouldn't result in two curves that share one action #36999
Existing FCurve interpolation methods are not really good for quaternions #45473

NOTE: this is a direct dump of https://wiki.blender.org/index.php/Dev:Source/Development/Todo/Animation (without cherrypicking the [still] valid items) ### Armature - [ ] Separate <s>and Join</s> tools should move animdata around too (using BKE_animdata_separate_by_basepath), see report: #31966 - [ ] B-bones (beziers) still use old code that keeps Z axis up, which causes twisting in cases. the solution as used for curve-deform could be copied here as well. #26090 - [ ] B-bones handling of rotations sometimes is wrong (hard to fix, maybe same/related issue as the one above, see #39491, #41678). - [ ] Armature editmode undo/redo issue: since armature edits sync with Pose all the time, a delete/undo command will still not retrieve all bone group, constraint and driver infos in pose-bones. #28350 - [ ] Skeleton Sketching does not correctly compute bone envelope sizes, resulting in near/effectively zero but non-zero size values. #34541 - [ ] Flip Names removes Bone numbers #34282 - [ ] Better handle of Pose transforms when applying Object-level transforms to data (#41699)? - [ ] The Dual Quaternions algorithm behind the "Preserve Volume" function (Armature Modifier) needs an update (#43188) - [http://rodolphe-vaillant.fr/?e=59 Paper] ### Rigging - [ ] Copy Menu - the future of tools like this is currently unclear. Certainly for rigging though, they are often the only useful way to do mass changes. - [ ] Proxy Objects (armature, group): the system works, but has limits. It can only proxy once (not duplicates), motion paths don't draw for it either (#26256). The feature was added in 2007 but never further upgraded or improved. - [ ] Proxy Bones: there's no or incorrect syncing of bone transform limits. #32116 - [ ] IK solver does not handle situations where you want only stretch when needed, would need to be implemented explicitly (report #32174) - [ ] Warning: if you use "Automatic weighting" (Laplacian "bone heat") you need to ensure the normals are correct, so don't use negative scaled models. - [ ] X-mirror for Armature editmode changes roll values on Transform, but with ESC it doesn't restore these rolls. - [ ] Setups with "Maintain Volume" modifier fail for some Bone rotations (work around included) #31975 - [ ] Can't undo hiding the bone #38911 - [ ] Bone '''Inherit Scale''' could be made to work with negative values #40506 - [ ] Automatic Weights are slow on high-density meshes #53494 ### Constraints - [ ] Constraints involving rotations - in particular, childof, transform, copy rotation - with influence < 1 are known to behave weirdly due to limitations with the underlying math. In particular, matrix decomposition issues mean that rotations are only guaranteed to be clamped to lie with +/- 180 degrees (causing issues with gears and other setups where the magnitude+direction of rotation matters), and negative scale factors cannot actually be individually identified with any accuracy. These are well known limitations of the current system, which are non-trivial and currently intractable problems. (e.g. #40671, #37623, #40873, and many many others before them) - [ ] PyConstraints - these are quite high on the priority list to restore, but are still waiting on a few technical issues to be resolved still - [ ] Transform Constraint functions quite limited. Postponed to fix. #27286 - [ ] Note: the "Child of" constraint functions best if the bone itself is not parented. - [ ] Bug report about "Child of" and "transform" constraints failing #29100 - [ ] "Apply visual transform" fails with IK constraint. #27743 - [ ] Mirror tool (Object mode) doesn't work for Child-of constraints always #32248 - [ ] Pivot Constraint is broken currently, doesn't function at all. e.g. #32963 - [ ] Copy Transforms constraint jumps when changing influence (especially when shear is involved) #34532 - [ ] Maintain volume constraint behaves wrong ({{GitCommit|48079) - [ ] Parenting object with constraint causes tansform ({{GitCommit|45531) ### Dependency Graph The 2.5 spec "animate everything" works, but what's missing is a clean dependency solver to ensure anything you relate gets displayed in real time on changing properties or while posing/animating. Here we collect known issues to solve later. - [ ] Driver example #26734 #35863 - [ ] B-Bone ease driver doesn't update well #28312 - [ ] Constraint with vertex group target on subsurf mesh not working #29059 - [ ] New dependency graph for all datablocks (Specially for all kind of material and texture datablocks, ie: Stucci parameters). #20956, #23426, blender/blender-addons#23639, #22698, #24562, #91015, custom props 3 #32495, custom props 4 blender/blender-addons#28286 - [ ] Bones and the object dependency graph? - [ ] Drivers using object data (e.g. lamp distance) do not update on changes immediately (#27424) - [ ] Image Sequence Not Updating in 3D Viewport when it's properties are driven with a driver (#30514) - [ ] Wonderful complex dependency of Cloth with Duplication and NLA #29838 - [ ] Dependency graph and layer switching error (#27032, #27032) - [ ] Group duplicators + deform, error related to drawing modes and layers. #24774 - [ ] Object has modifier dependency on an object inside a linked group. #26724 - [ ] Cloth sim inside a linked group updates badly (pointcache issue too). #27287 - [ ] Object uses a constraint dependency to an object inside a linked group. #27694 - [ ] Updates with custom properties very slow: #31647 - [ ] Proxy: needs to be created with group-instance on location where it starts - to make pointcaches work. #32944 - [ ] Multiple duplications of group, 1 proxy error: #31891 - [ ] Two scenes, in two windows, with partial shared data - bad updating. #33560 - [ ] Viewport dupligroup evaluated in original location, render dupligroup in dupli transformed location gives difference between viewport and render (#33591, #33595) - [ ] Instances linking to group that link to group with animated characters doesn't work. #34025 - [ ] Dupligroup with Array modifier but control object not in group. Undefined result. #35562 - [ ] Dupliframes on armature - armature cannot be posed once keyframes exist.#35929 - [ ] Lack of refresh on layer visiblity change #37262 - [ ] Changing texture doesn't refresh deform modifier #39717 - [ ] Drivers using own transform channels are not reliable #50066 ### Animation System Notes: - [ ] When constructing data paths, only use the "" form for strings. Even though Python supports both interchangably, we only use the <code>""</code> form for strings used for names. Using the <code>' '</code> form instead may lead to unexpected evaluation results. - [ ] Properties for GLSL shaders are not animated during anim playback, they are compiled for speed. - [ ] Driver test cases (should be in regression): #24012 - [ ] Opening 2.4x files with objects with shared Actions results in missing animations. - [ ] Unable to bake actions for multiple selected objects #38308 Todo: - [ ] Frame-mapping (map to, old) is still half implemented. Candidate to be removed? - [ ] <s>Remove animation data from objects, when all their animation is deleted.</s> - [ ] Non-relative vertex keys aren't really usable currently, see #22431 - [ ] Animation 'overrides', or some kind of functionality to keep recently changed (but already keyframed) values from changing on scene updates would be nice to have, see #26019. - [ ] Support for passing string/pointer values into scripted expressions using Driver Variables as containers for this blender/blender-addons#26306 - [ ] Animation playback: the way how the timer manages 'current frame' is not well implemented. Error for example happens when using redo-operator on playback. Needs revision. - [ ] Animating collections (like object layers): per-element curves might apply incorrect because of restrictions for overall collection, #29883 - [ ] An easy way to clear Custom and rig UI Proprieties from the selected PoseBone, setting up the default values - like Alt+R for Rotation. Alt+C looks to be a good hotkey to clear Custom Proprieties from PoseBones - [ ] Mirroring Bone Pose working for Bone Custom Proprieties and Custom UI Proprieties - [ ] Duplicate objects could check all RNA paths, and fix ID names in it for new names. #31161 #36626 - [ ] Changes such as selecting/renaming groups in anim editors don't affect bones. This was never meant to work, since "Group channels != Bone channels" (even though when dealing with bones, the default behavior is to group together bone fcurves to make them easier to find). Anyways, for usability, it would be nice to eventually get this sync working again. But, "Not-A-Bug-For-The-Tracker (TM)"!. Examples: #35798 - [ ] NLA Strips need "cycle offset" for the case where a strip gets split in the middle of a repeat. However, cannot implement this without a thorough unit test set for this code #27503 - [ ] NLA influence animation has to be done without EditMode on strips. Inside EditMode doesn't work yet (was meant for animating time). - [ ] Drivers duplication won't preserve targeted objects #39079 - [ ] FCurve easing could use normal of handles #39916 - [ ] Undo re-orders dope sheet items which have cyclic dependencies #38491. - [ ] Editing keyframes in Graph Editor currently does not force motion paths to get recalculated. #42181 - [ ] "Separate" shouldn't result in two curves that share one action #36999 - [ ] Existing FCurve interpolation methods are not really good for quaternions #45473

Added subscribers: @lichtwerk, @ideasman42

Added subscriber: @christian-clavet

Added subscriber: @BClark

Closing this task, as it is out of date (almost all linked issues are closed, but weren't checked off on this list) and the tasks that don't have an issue linked to them are very vague. It's a mixture of 'notes' and 'things to remember' without being clear about who has to do the remembering.

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Blender development todo list -- Animation System #55365

Armature

Rigging

Constraints

Dependency Graph

Animation System