For this is how God loved the world:
he gave his only Son, so that everyone
who believes in him may not perish
but may have eternal life.
John 3:16
Very recently I developed a plugin for Unity3D to deal with animation root motion. You can check the asset url: https://u3d.as/2F6K.
When I was dealing with exported animations to test the plugin I developed, I discovered that the Blender's exporter comes with two limitations: It does export a ghost root bone called 'Armature' and it does import one keyframe ahead of frame 0.
I made the modification in my Blender's installation and now I'm sharing the code here.
I extracted the textures using Blender.
When I tried to export only the mesh with the rig, I got an additional empty root bone in the hierarchy called 'Armature'.
The model I export is different from the model I imported...
This is incompatible with the Unity animation system, because the other animation files need to match the bone hierarchy.
Worst: when I turn on the 'Key All Bones' option in the current FBX exporter (2021), it creates an animation curve for the 'Armature' (the undesired root bone). This causes the Unity native root motion to stop to work.
This is not a fault of the original developers, because the Blender's API exposes the struct the plugin uses to export.
The 'Armature' is part of the Blender's data. And the original exporter just exports it as it gets from the API.
This image below shows the original model from Mixamo on the left side and the exported model from Blender default FBX exporter.
When we import from the current FBX, the importer adds 1 to every keyframe number on the Blender's timeline.
This causes the animation to have a 'hiccup' when we need to export it back.
The animation import problem is on top of the image and the correct animation frames position is on the bottom of the image.
I got the code from the Blender installation and started to search for the places (hierarchy and keyframe) we need to modify.
You can edit the files in the Blender's installation folder.
On Windows the files are:
C:\Program Files\Blender Foundation\Blender {Blender Version}\{Blender Version}\scripts\addons\io_scene_fbx\export_fbx_bin.py
C:\Program Files\Blender Foundation\Blender {Blender Version}\{Blender Version}\scripts\addons\io_scene_fbx\import_fbx.py
On Linux the files are:
/usr/share/blender/{Blender Version}/scripts/addons/io_scene_fbx/export_fbx_bin.py
/usr/share/blender/{Blender Version}/scripts/addons/io_scene_fbx/import_fbx.py
On MacOS the files are:
/Library/Application Support/Blender/{Blender Version}/scripts/addons/io_scene_fbx/export_fbx_bin.py
/Library/Application Support/Blender/{Blender Version}/scripts/addons/io_scene_fbx/import_fbx.py
The hierarchy itself was the most difficult part to figure out how to solve compared to the import part.
I removed all Blender's Armature from the object list to export:
# Objects (with classical parenting).
for ob_obj in objects:
# [Alessandro] Remove Armature node from export
if ob_obj.type == 'ARMATURE':
continue
...I added a code to check if the bone being exported is the real root bone (attached to the 'Armature' as its parent) and added it to the FBX without a parent node:
# Armature & Bone chains.
for bo_obj in data_bones.keys():
par_obj = bo_obj.parent
# [Alessandro] Set the parent of root null from the first parent bone... not the Armature
if (not par_obj is None) and par_obj.type == 'ARMATURE':
connections.append((b"OO", bo_obj.fbx_uuid, 0, None))
continue
...Finally I changed the animation name by removing the 'Armature|' from its beginning:
def add_anim(animations, animated, anim):
nonlocal frame_start, frame_end
if anim is not None:
# [Alessandro] Remove 'Armature|' animation name...
_astack_key, astack, _alayer_key, _name, _fstart, _fend = anim
# [Choccy] The original function only worked when the armature name is Armature.
# I change it a bit so it removed words before '|' and the '|' as well.
_name = _name.decode("utf-8")
if "|" in _name:
indexed = _name.find("|")
_name = _name[indexed+1:]
_name = _name.encode("utf-8")
animations.append((_astack_key, astack, _alayer_key, _name, _fstart, _fend))
...I decremented 1 frame index in the keyframe insertion part:
# Add each keyframe to the keyframe dict
def store_keyframe(fc, frame, value):
fc_key = (fc.data_path, fc.array_index)
if not keyframes.get(fc_key):
keyframes[fc_key] = []
# [Alessandro]
keyframes[fc_key].extend((frame-1, value))Blender 4.1 changed the animation frame position to another place.
Take a look at the snippet below:
def _convert_fbx_time_to_blender_time(key_times, blen_start_offset, fbx_start_offset, fps, fbx_ktime):
timefac = fps / fbx_ktime
# Convert from FBX timing to Blender timing.
# Cannot subtract in-place because key_times could be read directly from FBX and could be used by multiple Actions.
key_times = key_times - fbx_start_offset
# FBX times are integers and timefac is a Python float, so the new array will be a np.float64 array.
key_times = key_times * timefac
key_times += blen_start_offset - 1 #[Alessandro]
return key_timesI marked with the text # [Alessandro] in all the parts I changed in the source code.
If you don't want to install this version, you can do the changes by yourself.
I hope it can be useful.
-
Download the current release zip file from GitHub.
-
Open Edit > Preferences...
- Click Add-ons
- Click on Community
- Click on Install and select the release file you downloaded.
- Click on the checkbox to enable the Add-on
You can check if the add-on is installed correctly if you see the '@aRibeiro' in the import/export menu of the Blender as shown in the image below:
