Strap on your big boy pants and use Motionbuilder F-curves to fix bad mocap

Bringing in Optitrack mocap data I notice that I get errors with a character if:

a.) there are any gaps. Use the Fill Everything in Motive to fix unseen gaps in the timeline after you have gap filled – even if the timeline is 100% green tiny gaps  may not show up

b.) Some of the auxiliary markers eg the upper arm, not the elbow has a bit where it ‘peaks’ out  – even thou’ the ‘segments’ body look like it moves ok – it may cause an unwanted bone rotation in MotionBuilder. Turn the bones on in Motive to see if the bones are twisting and fix.

In Motionbuilder run the take on your characterised character.

If there is hand ‘flipping’, start looking at bones higher up – in the hand’s case start with the elbow. Zoom in on the f-curves. If there is a section in the Rotations that looks like it was lifted out of position up or down, isolate each of X,Y or Z and move the ‘lifted’ section back into position.

Fcurve section ‘lifted up’ or down

 

Click-drag over keys to make the section and drag the green area on the left to move it to the correct position – repeat for X and Z curves

if one section of the curve seems like it’s inverted like below…

Inverted section

…where the slope of the section appears to be going the wrong way i.e. slopes down not up, then select the section again – we’ll need to flip the section:

1. Grab bottom white arrow handle

Grab the bottom handle (white arrow) on the left and drag it above the other white handle like so:

2. Drag handle up to match the original curve

..and move it up so that the top of the selected curve section meets the original curve  (here it’s on the right-hand side of the selection). Then get the bottom handle and drag it up so the  curve matches on the left side of the section like this:

3. bottom handle to match selection to curve on left hand side

..And this has worked for me. You will probably need to go and fix the next limb down e.g the hand

For Gimbal issues this seems to affect hips, where there’s is a little jog, you might see it affect the character. in the Hips fcurve it may look like this  section- it’s not a straight-up lifted section like above and that technique won’t fix it.

Gimbal errors

…Instead select over the affected keys for one section – I’m picking the bit on the left:

Apply the Gimbal killer filter from the filters list- it makes the selection shrink down to a tiny area then hit apply. Should be good to go.

The main thing is to work out if it’s a flip section or a gimbal – flip section doesn’t have a shoulder – there is no curve at the edge its a clean break from 1 frame to the next.

Gimbal Killer filter applied – shrinks the selection to a small area

 

One more thing, if you cant see Gimbal killer in the filters list change the dropdown to Selected Properties like shown