Retargeting Optitrack data in Blender

[Ashkan]

Hello everyone. Recently we got a new Optitrack Mocap system at School of Art/University of Manitoba and started recording and saving data as .FBX and .BVH file, but we have problem in applying the mocap file on the 3D character in Blender. We use Auto Rig Pro and Rokoko plug-in to rig and retarget but every time the result is a mess. bones are not matched accurately and orientation of the mocap file and character are always different no matter how much we try to fix the orientation during the process of importing the FBX files.

Has anyone experience dealing with this subject? we could use some help on this issue for sure.
Is there a simpler way to do this? we are trying to coordinate a workshop for students about working with OptiTrack but the process seems to be so complicated and time consuming right now (without any result).

Any advise and guidance is appreciated.

Cheers,

[cge]

I’m using FBX files exported from Motive with ARP Remap and ARP rigs. Firstly, make sure you import your FBX with Animation > Automatic Bone Orientation enabled, or else the bones orientation will be all messed up. I get good results with IK feet to avoid foot slipping and FK for the upper body. IK for the upper body sometimes results in the elbows popping when retargeting from OptiTrack data with ARP in my experience, so best to retarget the upper body with FK first and then convert to IK as needed. I use the auto-scale feature to make sure the OptiTrack armature has the same distance from the hips to the feet as the target rig (it’s ok if the rest of the body doesn’t match for FK, but the legs matching is important for lower-body IK). Next, I use Redefine Rest Pose to ensure the OptiTrack armature starts in the same pose as the target rig, which is important for FK retargeting. After that, the retarget should succeed and produce good results in most cases.

Beyond that, the CGDive YouTube channel has excellent tutorials that will show you exactly how to do retargeting with ARP and get good results, which is where I learned tricks like Redefine Rest Pose. I believe the guy also has a Discord server where people can ask for help.