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Thread: IK Chain Shoulder Girdle Setup

  1. #1
    Digital Composite Rookie
    Join Date
    Aug 2016
    Posts
    155

    IK Chain Shoulder Girdle Setup

    Hey this is a write-up for an IK shoulder girdle joint chain.





    I made the shoulder girdle an IK chain just like the arm. Clavicle->Acromion->Scapula is treated like Shoulder->Elbow->Wrist.



    Outliner



    The only thing "outside" it is the point constraint from the Acromion joint to the Shoulder joint of the arm IK.

    I placed the shoulder girdle IK chain completely flat to be coplanar, and it hits at the root of the clavicle, Humerus, and sort of center of the top of the Scapular spine.


  2. #2
    Digital Composite Rookie
    Join Date
    Aug 2016
    Posts
    155
    The scapula-shaped NURBS deformer was added as a sculpt deformer with these tool settings. The last checkbox for "Use secondary NURBS or polygon object" is mandatory for this to work and it won't tell you if you forget to check the box. The deformation just won't happen.

    The scapula NURBS is parent constrained to the Acromion->Scapula joint. Select skin then deformer NURBS object->Sculpt Deformer.



    The sculpt node on the NURBS object is set to this. It's the same as the tool settings when I created the deformer, but you can change Envelope, Dropoff Distance, and Max Displacement to tweak the strength of the NURBS influence.



    Once you place your controller object for the IK handle, translating it laterally will push the shoulder forward in an arc.



    Your polevector will control the vertical movement of the shoulder



    From here you can set-driven-key X translate to control the scapula's lateral movement, and Y translate to control the polevector's range of motion.

    I like to group controllers and locators (and such) to keep their attributes at zero. You can still group those items again to add more influences and keep the object attributes at zero.

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