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Discussion and Support for the OptiTrack, SmartNav and TrackIR brands by NaturalPoint

Lag issues help

by Jonlimcff » Sun Jan 23, 2011 8:34 am

Hi working on an animation film now and trying to the vcs camera to select shots. When recording everything looks ok. When I playback however I seem to get a stuttering effect and a slight lag issue around a half second or so. I'm thinking perhaps my play blast layout has too much data? Or are my settings wrong? We are using the arena software in Maya and facing this problem. Anyone else got this problem? Seems like the more sensitive the movement the greater the stutter. E.g. When I slow the speed of the camera when I want to use a tracking shot I get a horrible stutter when I playback. Please help! THanks in advance
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by morgan » Tue Jan 25, 2011 12:56 pm

The new 1.2 Beta contains several fixes, changes and additions.

This release may address your issue.

In addition, it's important to note:

- The sample rate should match the mocap capture rate for the smoothest possible performance (typically 100 fps or 120 fps).

- Having said that, when recording, standard Maya settings usually record at 24 fps (film). For a typical OptiTrack setup at 100 or 120 fps, this means some downsampling must occur, which happens automatically in the plugin. In this case, quick camera moves may drop key frames. Maya's animation tools should allow you to smooth these curves out to achieve the desired effect.

Hope this helps,

Morgan
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by JustinDenton » Tue Jan 25, 2011 6:16 pm

Morgan's advice here was all very solid. We were running into the same timing issue recently as well, and it turned out to be the 100 vs 120fps issue Morgan was talking about.

Also, what are you using for your general maya playback settings? We have found that we need to set our timeline to real-time.

In regards to stutter, this is probably a byproduct of the sampling issue, as it might be laying keys on a subframe level. You can also resample your curve to help smooth things out or even bake the curve back to being on everyframe but make sure to have frame snapping on.
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by jonchiew » Wed Jan 26, 2011 4:14 am

Halon: we are doing 24 fps.

With the new update, the lag is gone.

However the Stutter was pretty obvious at first. We reduced the camera settings down to 100fps(in Tracking Tools) and the plugin's Sampling Rate to match it, everything seems smoother. The only incident that the stutter got worse when we are doing the combination of any 2 of these moves: panning, dolly & booming.

I am not sure how to do this - "You can also resample your curve to help smooth things out or even bake the curve back to being on everyframe but make sure to have frame snapping on."

In Maya or the VCS plugin?

Thanks for the help.
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by jonchiew » Wed Jan 26, 2011 4:25 am

Morgan

have a few more questions for the controllers.

Sometimes the camera sinks or rises on its own( i am sure no one is touching it).Is this normal?

The speed of the moves(P,D,B) is different before and during recording. For an instance, we adjusted the dolly speed to what the Director wanted during pre-runs(before recording), but during recording the dolly speed is much slower. How do I overcome this?

tks
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by morgan » Wed Jan 26, 2011 11:10 am

Re sink or rise, try disabling your pan up/down action to confirm its being caused by the controller thumbstick.

Also look at the live values the controller is reporting for that axis. The VCS plugin ignores a region around the center of the thumbstick axis (a dead zone). If the controller thumbstick return to center is still registering outside this dead zone, this would cause the pan behavior. If necessary we can expose the dead zone parameter so you can increase it for your thumbstick configuration.

RE speed of moves, yes this is a Maya issue. Basically during playback Maya samples at your Maya specified playback rate. If this rate is different than the VCS plugin's "Sample Rate", then your controller speed during Maya animation playback will be different than when Maya animation playback is not occurring.

We're working with Autodesk on this and hope to have an improvement for 2012. Until then the workaround is to set your VCS plugin's "Sample Rate" to match your Maya animation Playback rate, then controller move speeds will be identical. Note this may also make camera motion seem more "choppy" due to the decreased sample rate.

This is one area that MotionBuilder handles much better. If you have MotionBuilder I would encourage you to try it as well for comparison.

Morgan
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