WIP: world space copy/paste prototype #115675

Christoph Lendenfeld · 2023-12-01T16:42:41+01:00

Christoph Lendenfeld commented

2023-12-01 16:42:41 +01:00

This PR is not meant to be merged, rather it is an exploration to kick off discussion for such a feature.

Idea

When animating it is often needed to transfer the animation of an object into the space of a different parent.

You have animated the root bone, but now you need to transfer all that motion onto the hip + ik legs
Or you have animated an object in the space of a parent which itself has motion, but you want to bake out all that motion into world space.
Or you want to copy/paste animation between files and the hierarchy might not be the same.

That's where it is useful to copy animation data in world space.
You can then do the following workflow.

copy animation
do whatever changes are needed to the file
paste the animation back on and it will be exactly as before

Current Tools

Blender currently has the Copy Global Transform addon, which does a similar thing, but is limited to a single frame.

Ideally the tool to copy/paste animation will be implemented in C/C++ in order to be as fast as possible. The speedup will come from the ability to use a partial Dependency Graph to evaluate the scene, which should make the operator performant even in heavy scenes.
It also allows us to work with the keyframe array directly, which should be fast even with large mocap data files.

Design challenges

Which object gets which animation data.
It is clear when only one object is selected, or when the selection is the exact same between copy and paste.
But I can see a use case for pasting animation to a different set of objects, at which point you need to specify a mapping.
This might be only available through python, but allowing artists to specify that themselves would be very powerful.

Future Possibilities

By implementing a solid solution to store and apply world space data many more features will become possible.

unparent an animated object without it changing the animation in world space
sticking an object to another without parenting (paste with offset)
making sure objects are stuck in world space, even though their parent move
baking animation (exists but needs to step through the timeline making it slow)

Issues with this prototype

only works for single objects, even though a part of the code is set up to handle selection.
only for objects, bones would need to be supported as well
Using C to write a binary file to a location next to the user preferences. There might be a better place and a better way to do this.
skewed scaling probably won't work. But I haven't tested that. Probably fine to have that limitation

This PR is not meant to be merged, rather it is an exploration to kick off discussion for such a feature. # Idea When animating it is often needed to transfer the animation of an object into the space of a different parent. * You have animated the root bone, but now you need to transfer all that motion onto the hip + ik legs * Or you have animated an object in the space of a parent which itself has motion, but you want to bake out all that motion into world space. * Or you want to copy/paste animation between files and the hierarchy might not be the same. That's where it is useful to copy animation data in world space. You can then do the following workflow. * copy animation * do whatever changes are needed to the file * paste the animation back on and it will be exactly as before # Current Tools Blender currently has the `Copy Global Transform` addon, which does a similar thing, but is limited to a single frame. Ideally the tool to copy/paste animation will be implemented in C/C++ in order to be as fast as possible. The speedup will come from the ability to use a partial Dependency Graph to evaluate the scene, which should make the operator performant even in heavy scenes. It also allows us to work with the keyframe array directly, which should be fast even with large mocap data files. # Design challenges Which object gets which animation data. It is clear when only one object is selected, or when the selection is the exact same between copy and paste. But I can see a use case for pasting animation to a different set of objects, at which point you need to specify a mapping. This might be only available through python, but allowing artists to specify that themselves would be very powerful. # Future Possibilities By implementing a solid solution to store and apply world space data many more features will become possible. * unparent an animated object without it changing the animation in world space * sticking an object to another without parenting (paste with offset) * making sure objects are stuck in world space, even though their parent move * baking animation (exists but needs to step through the timeline making it slow) # Issues with this prototype * only works for single objects, even though a part of the code is set up to handle selection. * only for objects, bones would need to be supported as well * Using C to write a binary file to a location next to the user preferences. There might be a better place and a better way to do this. * skewed scaling probably won't work. But I haven't tested that. Probably fine to have that limitation ----- <video src="/attachments/b16cfa71-dd73-4713-b261-179a5eecff50" title="World Space Copy Paste" controls></video>

copy_world_space_prototype.mp4

1.3 MiB

Christoph Lendenfeld added the

Module

Animation & Rigging

label 2023-12-01 16:42:41 +01:00

Christoph Lendenfeld added 12 commits 2023-12-01 16:42:53 +01:00

1b5de35d95 working copy function

bec3ee3e9b store object and frame count on disk

975ad749c6 actually store complete struct data on disk

1a0597e987 reading the data back works

03a9f50306 extract functions