Feedback: 3dsMax Hybrid FK/IKsplineModifier Spine Rig...

#1

So I’ve finally gotten back to teaching myself rigging and I’ve created my first attempt at a combined FK/IKsplineModifier Spine rig. It is for an older game character rig for modding purposes… the released game character’s spine was built vertically so that’s just a constraint I had.

Anyway, the FK spine follows the guidance from Paul Neale’s rigging DVD set. The blue FK gyros control the blue FK spine (made with boxes so as not to be confused with the skin bones) for Y and Z-axis rotations (X-axis rotations are locked out). Selecting both FK gyros will permit you to rotate with a “flat back.” I forgot to rename the bones so…

Bone01 = Pelvis
Bone02 = Lower Lumbar
Bone03 = Upper Lumbar
Bone04 = Thoracic
Bone05 = spine nub
Bone06 = Neck
Bone07 = Head

The FK spine drives a NURBS curve via the Skin Modifier (an idea I saw in a GDC presentation by Steve Theodore for a Hybrid FK/IK spine). The Nurbs Curve also has an IK Spline Modifier on it for a pseudo-spline IK effect… following the general idea from Paul’s IK spline setup (except no stretchy bones). Bone01 is position constrained to one of the helpers (that is path constrained to the NURBS curve). The skin bones use LookAt constraints to Helpers that are path constrained to follow deformations of the NURBS curve caused by the Spline IK Modifier Knots and the box control shapes. The box control shapes deform the NURBS curve and also control the twist of the spine bones. The Upper box controls the twisting of the upper spine, lower box the lower and the middle control box twists the entire spine.

I also scripted the pelvis bone (Bone01) to rotate/swing as the Hips are swiveled via the Hips control star shape. I think this captures what the human pelvis does… but I’d like some feedback from the experts out there.

The only issue I seem to have right now is that the neck bone is orient constrained 50/50 between the Head and spine nub; and this causes the head to be thrown out-of-plane when the spine is twisted and I rotate the FK spine. It’s a subtle thing… and perhaps that is naturally what would happen… so looking for feedback on that as well.

Also, I’m debating about having the Box shape controls also rotate the upper and lower set of Knot helpers… not sure about this though.

Lastly, This is simply a concept test rig setup and the bones are not in the proper proportions to the actual game character… and was built offset from the origin because that is where the game character skeleton resides (although that has been removed from the file for clarity).

I would appreciate any constructive criticism/feedback. Thanks! The file is Max8.

EDIT: I forgot to lock out the translations on the FK gyros… so I’ve taken care of that in the revised uploaded file.

#2

One area that I have questions about is the number of CV’s I should have on the NURBS curve and how they should be distributed?

Originally, I had only the three bottom Knot helpers wired to the Lower Box control shape… but when I translated the Lower Box control I noticed that the pelvis bone (Bone01) was tilting inward-- this resulted in a nice spine curve but it caused the leg wrapper points to be rotated because of how I had their parent helper (“SpineLink”) constrained. I corrected the SpineLink helper to be position constrained to Bone01 and orient constrained it to the Hips Control so as not to influence the legs unless I was rotating the Hips Control. But I thought I should force Bone01 to remain vertical while translating the Lower Box control… so I wired the middle Knot helper to follow it.

Should the pelvis remain vertical when translating the Lower Box control? Or is it natural to have it tilt inward (as when I only had the three bottom Knot helpers wired to the Box control)? And if it should tilt inward, then should I re-parent the SpineLink helper to allow the legs to follow the tilt? What is correct for proper contrapposto?

#3

Shameless bump… where are the Rigging Pros & Technical Directors?

EDIT: In thinking on this… I believe it would be better to have the Spline IK Modifier’s Box Control objects co-located on the NURBS curve-- rather than offset and free floating like the FK spine control gyros.

#4

Double post…

#5

Hey,

I like the rig you’ve got and I think it’s an interesting twist on Paul’s, the FK spine trick is a nice way to get an initial pose.

There’s a few minor things I’d like to ask and suggest:

  1. Why are Point02 and Point06 required? Moving Point06 actually seems to have a negative effect on the rig when it’s moved.

  2. I think the positional and rotational weighting of the spine which is controlled by Shape01, Shape02 and Shape03 should be slightly adjusted. When Shape02 if moved, Point05 moves with it 100% and when Shape02 moves, Point04 doesn’t move and Point05 moves 100%

What I think would perhaps look a bit better would be if you had a fall-off in the control influence. So Shape01 controls Point01 and Point03 100% but controls Point04 50%, Shape02 control Point04 100% and Point03 and Point05 50%, Shape 03 controls Point5 and Point7 100% and Point05 50%.

  1. I found that it was easier to use the rig when CTRL_spine_lower and CTRL_spine_upper were Position Constrained to Shape01 and Shape03, respectively. But then I noticed that you’re using the Y- and Z-rotations of the FK controls and the X-rotation of the Shape controls - why not try to use one control which uses all three axis?

Fairly minor things overall, but I liked the set-up.

-Harry

#6

Thanks… but as a wise man once said, “There’s nothing new under the sun.” It’s not any new idea of my own… I’m just following Paul and Steve’s ideas/examples… I thought this Hybrid Spine setup (Paul has similar ones) that Steve presented a long time ago would work for me in what I’m trying to do… but I really like Paul’s rigs and teachings… so I tried to incoporate his rigging philosophy. Imitation is the greatest form of flattery they say… (If you don’t have his rigging DVD’s I would highly recommend them) but to your questions:

  1. I read that you needed to have enough control points at the ends of the NURBS curve to keep it more tangent at the pelvis and neck joints. I suppose Points 2 and 6 could safely be deleted… (if you had smaller length bones you wouldn’t want them to bulge out following kinks in the curve).

  2. It certainly could use tweaking… I was just hammering out the concept (my first attempt at an FK/IK spine).

  3. What I noticed was… is that if I used the FK control gyros for the spine twist as well… then when I wanted to rotate the spine purely forwards/backwards, or purely sideways… their spine-twist contribution caused the spine to swing way out-of-plane passing from one side to the other. So I moved the spine twist to the box shapes that handle the NURBS curve deformation-- this allowed me to twist the spine, yet keep the forwards/backwards or sideways bending (driven by FK) planar. Try it out and see…

P.S. I’ve since refined this Hybrid Spine idea (after getting some feedback from Paul for my specific application) and studying his Maxine rig that shipped with 3ds Max… basically I’ve moved the controls to be co-located along the spine and have an individual FK control for each skin bone (because I want to be able to retarget FK animations onto the rig)-- but I kept a master FK “auto-bend” control (something I saw in a Sergio Mucino tutorial…) and a master full-spine-twist control… both of these out in front of character-- separating out the twist for the reason I stated above (the individual controls can still tweak the spine as needed). I also added a look-at target for the head and it’ll have custom attributes to let the look-at target drive it or the FK head control, or allow it to be locked to follow shoulders (stuff you learn from Paul’s rigging DVDs, 3dsMax tutorials, etc.).

I appreciate your feedback… :thumbsup:

#7

Brad Noble’s Skeleton Rig is really good for deconstructing, there’s a lot of cool techniques he uses and the spine that he’s setup is really nice - it’s a hybrid spine with an FK mode, but crucially he only uses one control to effect its position and rotation, you might find it useful in the future.

-Harry

#8

Thanks, I’ll check it out. I agree it would be nice to have just a single control object…

#9

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