freemocap / BlendArMocap

realtime motion tracking in blender using mediapipe and rigify

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BlendArMocap

  • Detection of Mediapipe detection results in stream or video
  • Import of Freemocap mediapipe session data
  • Calculation of rotations for mediapipe data
  • Transfer of detected data and generation of new transfer configurations
    • currently, officially supports the transfer to generated rifigy rigs

Mediapipe Detection

Purpose

Run mediapipe within blender, detect pose, hand, face or holistic features. Calculate rotation data based on the detection results to drive rigs.

Setup Instructions

To run mediapipe, you need to install the required dependencies opencv and mediapipe via the add-ons preferences. Internet connection is required to install the required packages. It's recommended to disable VPN's during the installation processes. Blender may to started with elevated privileges during the installation process.

Apple User
Blender has to be started using the terminal if you plan to use the webcam on mac os as blenders plist doesn't contain a camera permissions request. Silicone mac users may need to download the intel version of blender.

Detection

Type
Select the data type you want to use as input:

  • Stream
  • Movie

Webcam Device Slot
If you have multiple webcam devices you may have to change the integer value until you find the device you want to use.
Defaults the Webcam Device Slot should be 0.

File Path
Select the path to your movie file. Preferable reduce it in size before starting the detection.

Key Step
The Key Step determines the frequency of Keyframes made in Blender. Adjust the Keyframe Step so the detection results in Blender match the recording speed.

Target
Select the detection target:

  • Hands
  • Face
  • Pose
  • Holistic

Model Complexity
Complexity of the landmark model: 0 or 1. Landmark accuracy as well as inference latency generally go up with the model complexity. Default to 1. The complexity level 2 for pose landmarks is not available due to googles packaging.

Min Detection Confidence
Minimum confidence value [0.0, 1.0] from the detection model for the detection to be considered successful. Default to 0.5.

Start Detection
When pressing the Start Detection button a window will open which contains the webcam or movie feed and detection results. The detection results are recorded in Blender at runtime. You can modify the recording starting point by changing the keyframe start in Blender.
May deactivate the rig while detecting if you have transferred animation results previously. To finish the recording press 'Q' or the "Stop Detection" button.

Starting Blender with elevated permissions

Installing dependencies may requires elevated privileges.

Windows
Right-click the blender application and choose: "Run as administrator"

Mac
Start Blender as admin by using the terminal:
Navigate to Blender: cd /Applications/Blender/Contents/MacOS
Run Blender as admin: sudo ./Blender

The Terminal request may be blocked even with elevated privileges, if that happens navigate to System Settings > Privacy and Security > Full Disk Access then activate your Terminal. After doing sudo shouldn't be required anymore. Run Blender: ./Blender

Linux
Start Blender as admin using the terminal:
Navigate to Blender: cd /usr/bin
Run Blender as admin: sudo ./blender

When running Blender as admin using sudo in the terminal, it's required to enter the admin password. Once the add-on packages are installed and your terminal has the permission to access your camera, you can start Blender with just ./Blender.

Freemocap import

Freemocap session data can be saved in a folder which then can be import using BlendArMocap. To import session data to blender, set the path to the session directory and press the import button. There are several import options:

Import Session
Import and process data while updating blender by default.

Quickload Toggle
Imports the data in one call - faster but blender gets frozen.

Raw Toggle
Load raw data - only available if Quickload has been toggled. May not be used to animate rigs - mainly for scientific usuage.

Load synch videos
Imports session videos as image planes.

Transfer

Concept

Mapping instructions are stored as object properties and can be modified in the objects constraints panel. Only valid for objects containing a specific cgt_id property.

Transfer Motion (3D View Panel)

Armature
Select the target armature (b.e. a generated rigify rig for the default config).

Driver Collection
Select a collection containing driver objects - cgt_Drivers to transfer all. In some cases you might want to just transfer pose, hands or face results - in this case select a specific collection to do so.

Transfer Type
Select a transfer type - current support default type is:

  • Rigify_Humanoid_DefaultFace_v0.6.1

Load
Loads the currently selected type to the transfer objects.

Save Config
Save a new config based on the objects in the cgt_Drivers collection.

Transfer Animation
Load currently selected config for objects in selected collection and transfer the data.

Setup New Configs (Object Properties Panel)

The setup process is quite unique, so lets break it down in steps. Objects which have been generated during detection contain an ID to display some additional properties in the object properties panel. Those can be modified to either change current mapping properties or even create completely new configurations!
Of course, you can just modify an existing config to improve mapping results ;)

Concept

mapping_object: object with instructions and constraints
driver_object: generated driver based on instructions
target_object: copies values from driver_object via constraints

Target

Target bone or object which should be driven by constraints.

  • Target Type [Armature, Mesh, Any]: Apply constraints to target (copies constraints from this object)
  • Sub Target [Object, Bone]: Target may be a Bone.

Drivers

There are three core concepts to set up drivers. In a nutshell [Remap Drivers, IK Chain Driver, Remap by Distance Drivers].

Remap Drivers
Object values (especially rotations) may get remapped using a remap driver. To do so, navigate to Value Mapping and select the properties you want to remap - for example rotation x, y, z.
From min, from max, to min, to max is used to define slopes, those are similar to the map range convertor node in the shader editor. Therefore, input the min and max values in radians from the selected object and the to min and max values in radians you want to have as result. (pi = 180°) If necessary, you can also use the factor and offset however, slopes can deliver better control once you got the hang of them.
You can do so for all axis separately if necessary, press the + icon to do so.
To get some information about the current select object, navigate to Tools and press the Log Object Info Button, you'll find min and max values from the object in the info panel.

# without remapping object
slope = (to_max - to_min) / (from_max - from_min)
offset = to_min - slope * from_min
f(x) = (slope * property_value + offset) * factor + offset

# with remapping object
slope = (to_max * remapping_value - to_min * remapping_value) / (from_max - from_min)
offset = to_min - slope * from_min * remapping_value
f(x) = (slope * property_value + offset) * factor + offset

IK Chain Drivers
The idea of ik chain drivers basically is to construct an ik chain in reverse order.
The end of the ik chain neither has a parent and nor gets remapped - it's mainly a reference. The next chain link has the chain end as parent, and gets remapped by the bone length which separates itself from the parent. Repeat this till you are at the ik start. As Example:

objects: shoulder_obj -> elbow_obj -> hand_obj
bones: shoulder_bone -> elbow_bone -> hand_bone

shoulder_obj(target=shoulder_bone, parent=None, remap_bone=None)
elbow_obj(target=elbow_bone, parent=shoulder_obj, remap_bone=shoulder_bone.length)
hand_obj(target=hand_bone, parent=elbow_obj, remap_bone=elbow_bone.length)

Recursivly applies:
dist = distance between parent and obj
f(x) = (dist / remap_bone_length) * (obj_location - previous_chain_obj_location)

Checkout the rigify rig implementation of the arms as example setup.

Remap Drivers by Distance
When using remap drivers by distance, we aren't using any of the object values. In this case, the distance between two objects gets used as driver value, which then gets remapped similar to the remap driver. The single difference is that the offset gets multiplied by the remapping value, which allows to basically offset in % (which usually isn't wanted for rotations). However, this time it makes a lot of sense to remap the value by a bone of the target armature as we are working with position and not rotation data - this makes remapping the values a lot easier. Again, to get some information about the current select object, navigate to Tools and press the Log Object Info Button, you'll find min and max values from the object in the info panel.

slope = (to_max * remapping_value - to_min * remapping_value) / (from_max - from_min)
offset = to_min * remapping_value - slope * from_min
f(x) = (slope * property_value + offset) * factor + offset * remapping_value

Constraints

Finally, add constraints to the object - the constraints will get applied to the target when transferring. As mentioned in the beginning, the target objects copies values from the driver using constraints. You may use any constraint to do so and modify the constraint properties to your likings to adjust transfer results. Wow, you got though - congratulations! Hope you'll make some awesome transfers! :)

Tools

Transfer Selection
Run transfer only for selected objects. When transferring chains the entire chain has to be selected, not just a link.

Smooth Animation Data
Run Blenders internal smooth f-Curves for selected objects.

Log Object Info
Log min, max values and information about the selected object to the info panel.

I/O Transfer Configuration (Topbar Import/ Export)

Transfer configurations can be imported and exported. If you create a new configuration and want to share it with the community let me know via hello@cgtinker.com <3

License

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

Copyright (C) Denys Hsu - cgtinker, cgtinker.com, hello@cgtinker.com



For tutorials regarding my tools may check out my YouTube-Channel. If you want to support me you can become a Patreon.

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realtime motion tracking in blender using mediapipe and rigify

License:GNU General Public License v3.0


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