Optical MoCap systems use two or more calibrated cameras to track markers on a mocap actor or prop. The tracking data, and the known location of the cameras allows software to determine the 3D location of each marker by triangulation. I wanted to try using Mocap, but I didn’t want to buy a Kinect or other hardware.
Blender’s tracking abilities have improved so much recently that it seems that it’s standard functionality can be used to do most of the calibration and tracking functions required for a mocap session. It just needs the bit that uses the tracking data from more than one movie clip to locate the markers. I thought someone must have done this, but I haven’t been able to find any examples (please tell me if I’ve missed this!)
It sounds pretty easy compared to what Blender already does. I have somewhat limited scripting skills, but I’ve made a ‘Triangulate’ addon to do this function. Before running the addon, it’s necessary to have set up two or more movie clips with tracking data for the markers on a mocap actor. There must also be matching 3d cameras in a 3d scene which accurately match the location, rotation and lens/sensor data of the real cameras which produced the movieclip footage. There are some rules relating to the naming of the elements in the scene covered in the documentation.
The ‘triangulate’ addon will combine the movieclip tracking data with the 3d camera locations, and will add keyframes to a series of empties to make them match the 3d position of the actor’s tracking markers.
The Empties can then be used by the 3d artist to drive an armature, or any other purpose. The built-in ‘Motion Capture’ addon can also be used to retarget the captured actions to a target armature or rig.
The Zip file contains the Triangulate.py addon file and a documentation text file.
Triangulate.zip (6.44 KB)
Edit: Now updated for Blender 2.8
Github page with download links
I’ve made a half-hearted demonstration video that might give you some idea how this works. It’s a bit quick to be a tutorial - I hope there’s enough detailed information in the ‘Documentation.txt’ file in the download to explain exactly what’s required. Also, the video refers to the name of the addon as ‘CamCap’. After I did this I thought ‘Triangulate’ was a better name as it’s by no means a full MoCap solution.
Note that the setup of the cameras in the 3D scene to match the real cameras is the critical step, and this addon doesn’t do this for you. I’ve started to think about a calibration function to help align the cameras to one mater camera that might make this easier.