anyone actually using optical mocap at the indie level (Optitrack, Vicon), or has inertial just caught up

The post-processing overhead argument was more true a few years ago than it is now. Motive has gotten meaningfully better at auto-labeling and gap-filling in recent releases. You still need cleanup passes, but the "you'll spend three times as long in post compared to inertial" comparison doesn't hold the way it used to, at least not if your actor isn't doing high-occlusion or fast spinning work where markers genuinely disappear.

The real blocker at indie scale is still calibration time and physical space requirements. Setting up and wanding a volume for a one-off session is nothing like pulling a Rokoko suit from a case. Per-session overhead is just inherently higher with optical. If you're running sustained production with a permanent calibrated setup, the calculus changes, but that's a different context than most indie projects are actually in.

This is a fair point but I think you're underselling how much the calibration process matters here. With optical at indie scale, the real bottleneck isn't the hardware — it's the time spent cleaning markers after every take. We ran a small test with six cameras and the cleanup on a 30-second clip took longer than the capture itself. At that point you have to ask whether the data quality justifies the pipeline overhead versus just hand-keying with good reference.

Yeah the floor reflections thing wrecking optical systems in home setups — I tried mounting retroreflective markers in my living room and the laminate floor produced so much noise the tracking was basically unusable below knee height. Ended up laying down matte black fabric across the capture zone which helped a lot, but it's one more thing to manage. Inertial suits don't care about any of that, which is a real practical advantage when you're not working in a purpose-built space.

the part about retroreflective marker placement is something i wish someone had told me earlier. we lost a whole capture session because we had markers too close together on the forearm and the solver kept swapping them during fast rotations. ended up using asymmetric cluster patterns after that and it made a huge difference. what software are you using for the solve step?

the hip rotation drift you described in optical systems — we had almost the same issue and traced it back to the solver treating the sacrum marker cluster as a rigid body when it's not quite. small amounts of skin movement over the pelvis during locomotion were being interpreted as rotation. adding a fourth marker to the cluster and switching to a least-squares fit for the rigid body solve brought the drift down significantly. what solver are you using for the rigid body step?

The matte black fabric trick for floor reflections is something I've been doing for about a year now and it makes a real difference. Worth adding: if you're seeing noise specifically in the lower leg markers even with the fabric down, check your camera exposure. Optical systems get confused by motion blur on fast leg movements if your shutter speed is too slow. Bumping to 1/500 on the capture cameras cleaned up a lot of my below-knee noise without any other changes.