Lately, I've been recording longer sequences which I intended to edit into shorter shots. This approach is working well except where the PS Move controller is involved--it seems like after a 1000 frames or so, the rotation starts to drift, resulting in some odd hand positions. Is anybody else seeing this behavior?

Is this drift caused by the length of the recording--1600 to 2000 frames--or could it be that the rapid hand motions are too fast for this type of capture? (The characters are playing musical instruments.) I don't have time to do specific tests for this right now so I was wondring if anybody else has experience with this issue or any ideas maintaining controller accuracy in long recordings.

Also, any suggestions for correcting the drift? I'm probably going to fix this in Motion Builder but if it can be done easily in iPi Mocap Stuido, I'd rather do it that way.

Thanks in advance for any helpful thoughts.

G.

_________________
Greenlaw
Artist/Partner - Little Green Dog | My Demo Reels (2013,) (2015,) (2017,) and (2019)

Watch a one minute excerpt on Vimeo now!

I'm thinking now that, instead of trying to do the hand motion for the entire duration in one pass, if I break it the motion up into smaller ROI's and make any necessary adjustments as a progress to each ROI before applying the motion data, it will probably be okay. More later as I work through this.

G.

_________________
Greenlaw
Artist/Partner - Little Green Dog | My Demo Reels (2013,) (2015,) (2017,) and (2019)

Watch a one minute excerpt on Vimeo now!

When properly calibrated, PS Move should not provide any drift in time due to using of magnetometer.
Possible problems include:

• Magnetic field conditions changed since last calibration. Don't know exactly whether it can lead to drifting, but definitely can affect accuracy of measurements.
  Solution: recalibrate before shooting.
• Magnetic field near the actor changes while recording. I've noticed that approaching large TV set (even when it's off) may cause some distortion in orientation.
  Solution: keep all big electronic stuff far from capture area.
• Orientation values may lag when doing some very quick motions, though we did not see that in our tests.
  Solution: move the sensor a bit slowly :)

Another way to solve drifting issue for long records, especially when using Wii Remote. Make the aiming at a camera in the beginning of each part of your shooting. Then you can make separate matching of sensor with camera for each (short) part.

Thank you for these tips! This info should be added to the wiki.

Before tomorrow's shoot, I should recalibrate the controllers--it's definitely been a while since I last did that.

In my case, I think what's also happening is that my grip gets a little 'sloppy' during in the course of the performance (characters playing musical instruments.) When I made a conscious effort to grip firmly, the 'drifting' seemed to stop--unfortunately, it also made the performance look 'stiffer'. I don't think I would have noticed this issue if this particular motion did not have a repeating pattern. I'll look into building a glove rig this weekend--that should help.

I'll also try re-pointing the controllers after the performance so I have an optional orientation to choose from--thanks for this suggestion.

FYI, I tried moving the BT adapter even closer to the performance area (it's attached to a repeater cable,) and this seems to help too.

G.

_________________
Greenlaw
Artist/Partner - Little Green Dog | My Demo Reels (2013,) (2015,) (2017,) and (2019)

Watch a one minute excerpt on Vimeo now!

I had the same problem with my PS Move. At first the controller rotates normally but over time its direction becomes distorted.

i noticed that the ps-move is VERY sensitive to ANY magnetic things. you have to make sure that the actor is not wearing any sort of metal on his body (rings, belt-buckle, etc), as well as stay as far away as possible from anything that can possibly influence the ps move.

in my experience, the longer a controller is influenced by something, the more likely he starts to drift and you have to recalibrate. i think the strength of the influence also plays a role here. when i started out with the ps-move calibrations, i always did them on my table, until i figured out, that even the metal-feet of our table had great impact on the calibration.

I think I noticed a similar issue here. In my case, it was with the Sister character and her cowbell. If the striking was too quick and snappy, the rotation would move off at some point. If the striking was more deliberate while keeping with the beat, the rotation stayed mostly on target--however, the motion also looked a little stiffer (because the real motion actually was stiffer.) I decided to go with the latter and tweaked the motion curves a little in Motion Builder to loosen it up a little.

As you may have discovered, moving the bluetooth adapter closer to the performance may help with accuracy. It appears to help in my situation--I used an extra repeater cable to move the adapter right next to the performance space.

Besides removing any magnetic field interference as described above, I'm not sure there's much else you can do to improve capture as this is probably a limitation with the PS Move device.

Just a thought: it might help to calibrate the devices while holding them inside the capture space, just in case there is interference coming from your PC or monitor.

G.

_________________
Greenlaw
Artist/Partner - Little Green Dog | My Demo Reels (2013,) (2015,) (2017,) and (2019)

Watch a one minute excerpt on Vimeo now!

To clarify, the main issue I had with the 'cowbell' problem was my grip. When playing, I had the tendency to hold the striker loosely. This is a mistake because if the striker moves independently in anyway from the wrist angle, the data will be inaccurate for the actual wrist rotation.

My solution was to grip the striker tightly so that it's rotation matched my wrist movement. This causes the performance to be slightly unnatural but at least the wrist capture is more accurate.

My guess is that you're running into the same issue with your grip on the 'drumsticks' (PS Moves). Try gripping them firmly and keeping them fairly locked to your wrist movements. It will feel unnaturally for actual drum playing but with practice you may get a more correct mocap performance out of it.

Just a few thoughts. Hope this helps.

G.

_________________
Greenlaw
Artist/Partner - Little Green Dog | My Demo Reels (2013,) (2015,) (2017,) and (2019)

Watch a one minute excerpt on Vimeo now!

That's weird that it's just the right hand. Anyway, keep us informed on how it goes. Hope you get it figured out soon.

G.

_________________
Greenlaw
Artist/Partner - Little Green Dog | My Demo Reels (2013,) (2015,) (2017,) and (2019)

Watch a one minute excerpt on Vimeo now!

i totally second that. the only thing i can think of furthermore is to try and move your capture space somewhere else. i had the drifting issues when there was something close by that was influencing my PS-moves. after getting away from every metallic object, as well as from live wires and anything that uses electricity as far as possible, my results improved a lot.

also, did you try to swap the motion controllers and record the left hand with the right controller? if yes, did you have the same problem?