I’m a fairly new MB user and in the past few weeks I’ve been getting into using the various Motion Builder Constraints for a short film project. I have a few questions about a particular Constraints setup and I am hoping that somebody here can help me.

I’m creating an animation of a cat playing a harmonica and there is mocap data for the entire body except the head and neck. I have an aim constraint to help me animate the head manually, and I’m using a parent constraint on the harmonica to attach the instrument to the character’s left paw. There is a ‘Lips Target’ null parented to the front of the harmonica and a ‘Lips’ null parented to the head control effector and positioned at the lips region of the face. The ‘Lips’ null’s position and rotation exactly matches the position and rotation of the ‘Lips Target’ null on the harmonica at frame 100. I also have an IK Constraint setup with the Neck as the First Joint and the Lips null as the End Joint, and the Lips Target null on the harmonica is the Effector.

What I want to do is have the IK Constraint take over the head motion at frame 100 so that the character’s ‘lips’ and head follows the ‘lips target’ null on the harmonica as the character’s paws move the harmonica. One more thing, I want the head to only track the ‘Lips Target’ null in a forward motion because the harmonica needs to slide across the lips from side to side.

So I was wondering, how can I limit the IK Constraint to rotate neck and head joints only on X rotation to get this forward only movement? Or am I using the wrong type of Constraint for this?

One more question: I’m using a Relations Constraint to animate the character’s tail, and it looks fantastic. I would like to add ground collision though and I’m not sure how to do that. Just to see what happens, I tried adding an IK Constraint to this setup which has the option to add the ground. This sort of works but not exactly, and I know what I did is just a hack. Does anybody have tips and information on how to set up ground detection for joints using the Relations Constraint?

Thanks in advance for any helpful information. (And please feel free to assume I know almost nothing, which is almost true.) :)

Greenlaw
Artist/Partner - Little Green Dog | Senior Digital Artist - Rhythm & Hues Studios
Brudders - Episode 54 ‘Star Snores’ | Hello Frankenstein

Okay, maybe I have the Reach T/R for the Head effector the Control Rig keyed incorrectly. Will post again once I’m sure.

G.

Greenlaw
Artist/Partner - Little Green Dog | Senior Digital Artist - Rhythm & Hues Studios
Brudders - Episode 54 ‘Star Snores’ | Hello Frankenstein

Hmm. Might have to drop using IK Constraint for the head, at least the way I have it implemented, because the head actually seems to ‘follow’ the harmonica better without the constraint.

But without a setup like this, the head and neck motions will need manually keyframed tweaks throughout to keep the lips ‘locked’ on the harmonica. (Remember, the original mocap does not have head or neck motions, so it’s really not following the harmonica at all.) I really want to avoid doing this if possible so I’m still looking for suggestions if anybody has one. Thanks!

G.

Greenlaw
Artist/Partner - Little Green Dog | Senior Digital Artist - Rhythm & Hues Studios
Brudders - Episode 54 ‘Star Snores’ | Hello Frankenstein