View Full Version : 3 Motionbuilder Questions

08 August 2006, 10:23 PM

I`m consedering to make a swich from Maya to MB, I have some questions befor making the final decision:

1. How can I creat a walk in place animation from a mocap file of a guy walking?
2. Can I access and tweek Fcurves althoug I work in story mode
3. Is there a filter or some other way I can smooth out the jittery motion in a mocap file


08 August 2006, 01:11 PM
1. How can I creat a walk in place animation from a mocap file of a guy walking?

For just viewing an animation on the spot but not actually changing the animation, go to Character settings Modifiers > In Place then check the which plane you want to lock.

If you want to create an actual walk on the spot animation there's two ways of going about it. These methods will both place it on the spot and also loop the animation...

i. Plot your animation of the character walking through the scene to the skeleton. Select all the bones in your skeleton (usually best to do this in the schematic view). Alt drag the selected bones into the Motion Blend window. Make sure the start of the cut is at zero and then click Adjust Start End to match the timeline limits to your cut length. Click Duplicate, to copy the cut, then making sure that you're on the first frame, click Insert, to insert a pose at this frame, and then Start Pose, so set that frame as the start pose. Drag the square box in the new cut preview at the bottom all the way over to the right to make the blend go over the whole course of the animation. Now click Duplicate again to copy your pose cut. Click on the pose (next to where it says B), to select it, and then click Stop Pose twice, so that B appears at the end of the preview cut. Drag the blend box for B, all the way over to the left to make the blend go over the whole course of the animation. You should now have a your animation looped on the spot. Just click Process, to plot the result to a take, and then go back to the Character Settings window and plot the animation back over to the Control Rig.

ii. The other way to do this is to set the timeline to frame 0, go to Layer one, create a full body key, then create a pose of this frame in the Pose Controls window. Now go to the last frame of your animation, turn off Match T and R in the Pose Controls window, paste the pose you just created, and then set a full body key on this last frame. The animation should now be looping on the spot, so you can now bake the layers down by clicking Remove in the Layer window, then Merge All and then Merge in the dialogue boxes that pop up.

2. Can I access and tweek Fcurves although I work in story mode?

The story mode is only meant for cutting, rearranging and blending animation clips, in the same way that you might edit a movie in a video editing program. It's not meant for actually animating and editing with keys and curves, and there's no functionality in there to support that. When you have clips in the Story Editor the results of the Story Editor will override any animation displayed in the viewport, essentially making it impossible to animate with keys while the story tab is open.

So the answer is that yes, you can edit the Fcurves while story mode is open, but you won't see the results of those changes because your on screen character will be driven by the Story clips, not the keyframes and curves of your animation. If you want to be able to animate you should make sure that there are either no story tracks in the Story Editor or that they're all set to mute.

3. Is there a filter or some other way I can smooth out the jittery motion in a mocap file?

I try to solve as much jitter issues before the mocap data ever gets to Motionbuilder, as it's generally easier to clean things up in IQ than it is in Motionbuilder. That's not to say that you can't do it in Motionbuilder though.

First things first: before you plot your animation from your actor over to the control rig, in the Character Settings tab, in the window with all the rollouts, go to Modifiers > Roll Extraction, keep the Roll Extraction mode on relative, and turn all these tickboxes on and all the sliders up to 100. This can really help solve any slight jitters in the arm and leg twist.

The rest of the work you can do with filters. If the filters window isn't already open, go to Window > Filters to open it up. The way I have my UI set up, is I have my Viewer and Timeline on my main monitor and all my tools on my second monitor, so I usually just sit the Filters window next to the Fcurves window and solve any jitter by selecting the appropriate keys in the Fcurves window, then applying filters to those keys to solve the jitter issues.

There are explanations of what each of the individual filters do in the Motionbuilder documentation, but the ones that I use all the time to nuke jitter are Butterworth (to smooth out any small dents in the curves), Smooth (to make a general smooth on curves), Peak Removal (to nuke any sharp spikes in the curve or any sharp peaks that should be smooth), and Key Reducing (to reduce the number of keys that are used to represent the curve). In most cases you would use these on targetted areas of the animation, rather than the whole animation, as you want to keep as much of the original data as possible.

Of course if all else fails you can often solve your problems by simply deleting the whole section of keys during which the jitter is occuring, as that section of animation will then just be replaced by interpolation, which is, of course, always smooth. You just have to make sure you keep any important keys that are defining the curve.


Anyway, hope all this has helped you (and anyone else reading), and hopefully you'll be able to get some better results out of your mocap cleanup from now on. :)

08 August 2006, 01:56 PM
a little addition to part 2. You can see the changes made in Story in cases where you do the keyframes in the Story. If you are using Additive or Override character tracks or animating stuff with generic animation tracks or Constrait tracks you can find the keys in the Fcurve editor...but as Headless said you can't make any changes in Clips that are brought to story.

If you look at the picture the you can the Cube is Alt dragged into Story and the big A (Accept keys) is turned on. Now if you animate every time you press K (key) keyframe goes to the specified track. Clip or cube selected you can find the keyframes in the Fcurve editor. Editor shows you also the lenght of the selected clip. Same thing works with the character when you have the caharacter track and a sub-track with A pressed can additively (or override) tweak the original animation. When choosing the track you have made you can again find the keys in the editor.

Greetings Finland and UK!

08 August 2006, 07:39 PM
...and suddenly the sky become a lot brighter :)

Thanks for these excelente answers!!!


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