I’m running into what looks like an interpolation issues with in MoBu 7.5.2.

Here’s the set up - I have a scene that’s designed to be played back at 24fps.
The actual scene - when played back in No Snap mode - fluctuates between 30fps and 20fps (ish).
I have an input device that’s sampling at 60hz - 60 times a second - and is inserting those values in the rotation curves of the camera at 60hz, even though playback is designed at 24 fps.

While MoBu is smoothing out playback, every now and then we get tiny hitches - on the order of, say 3-5 ticks, where the rotational information doesn’t appear to be being played back correctly.

Now the curves behind the rotational information are fine - totally smooth. The glitches are purely in playback (or record) and it looks like it’s something to do with the actual in MoBu interpolation code that is determining where the camera should be positioned and oriented for each individual frame. It’s way more noticeable when it goes below the rate at which the initial scene is set up (ie 24fps) and the glitches themselves occur at random intervals (it doesn’t look like this is result of more coming into the scene) and is not reproducible in terms of the same place in the time stream.

Anyone got any thoughts on this? While we are getting clean curves out of this process the fact that it’s a bit glitchy is of constant annoyance to our Director of Photography and Director on the movie I am working on - they want it to be 100% smooth and I’m tasked with getting it there.

What might be going on in the background??

What kind of hardware are you running on? is vert. sync disabled on the card or not? sounds more like a video card glitch maybe?

Does it happen when you set the FPS to 60 and record, same issue? (you can always sample high and down convert to 24 later.

Brad Clark
Co-Founder: Rigging Dojo-Teaching the art and science of character rigging
Author: Inspired 3D Advanced Rigging
The Character Animator Toolkit for Motionbuilder :available now:

I think I’ve seen this before. I’m not positive, but I think this is an issue with the way MOBU refreshes the scene in No Snap mode.  Even though you are set to 24fps, I think that only guarantees the interpolation values on those specific intervals.  In other words, it’s my belief that when you set the scene to No Snap, Mobu doesn’t guarantee the sub-frame interpolation values because it is trying to play back as fast as it can, unsynced to anything (other than the video cards vsync) so the refreshes vary sub-frame to subframe and won’t be constant.

I never play things back on no snap.  Mainly because I want people to see it at the film cadence only and not include the subframe because it’s a bit misleading, coupled with the fact that theirs no sub-frame consistency as far as I know.

Maybe someone from Autodesk and clear this up for us.