[Maya]Rigging 10 - Spine IK

Keywords: Animation, Maya Rigging, Spine IK system, Spine FK system

Maya Rigging series of articles:

Stage 1: Spine FK system

See: [Maya]Rigging 09 - Spine FK

Stage 2: Spine IK system

1, Create controllers for IK joints: ctrl_hip_ik, ctrl_shoulder_ik, ctrl_chest_ik and ctrl_pelvis_ik.

2, Setup the visibility for IK controllers in Node Editor for IK FK switch.

3, Unparent all IK controllers, because we need to manipulate the transformation of them later.

4, We will Reset Transformations later, but make sure that the Offset Parent Matrix has been cleaned before do that.

Because I had tweak the pivot of ctrl_pelvis_ik before, so to be safe, it is best to clean the Offset Parent Matrix.

You can tweak the rotation of controller if it’s orientation was wrong after Offset Parent Matrix.

5, Then Reset Transformations all controllers to place them at the origin of coordinate axes in world space.

Reset Transformations will zero the translation and rotation and normalize the scaling.

6, Duplicate the IK joints that we created earlier.

Then cull the unnecessary joints, only remain joints for shoulder, chest and pelvis.

Rename the IK joints at last: ikjoint_shoulder, ikjoint_chest and ikjoint_pelvis.

We can also tweak the Radius of joints for better visualation.

And give a special color for these joints.

7, Create an empty group at origin of coordinate axis, and we will use it as a reference afterward.

8, Match Pivots of joints to the origin of coordinate axis. (Check Rotate and Orientation)

9, Offset Parent Matrix of all IK joints to clean the transformations. The controller’s Offset Parent Matrix had been cleaned before.

10, Create a curve for spine IK system, we use EP Curve Tool to create it.

Using 3 Cubic to make the curve more smooth.

11, Hold V, then left click all the joints one by one, hit enter to finish it at end.

Rename the spine curve.

12, Create IK Spine Handle.

Uncheck Auto parent curve and Auto create curve.

Then click pelvis joint, then click the neck joint, then select the spine curve at last.

Now the Spine IK Handle has been created successfully.

We can move the vertex of spine curve to test if it works right.

All the joints of spine must be clicked when creating Spine IK Handle, otherwise the skeleton will deform sightly.

13, Bind Skin for IK joints. Select Selected joints for Bind to.

Now we can manipulate the IK system using IK joints.

14, From this step, we will demonstrate how to bind controller which pivot was modified.
Match Translation from shoulder controller to ikjoint_shoulder first.

15, Now we will modify the pivot orientation of ctrl_shoulder_ik, make sure Bake Pivot Orientation was checked before do that.

Then tweak the pivot position of ctrl_shoulder_ik. (Hold V when moving pivot)

You will see the Local Rotate Pivot and Local Scale Pivot have been modified.

16, Then move the ctrl_shoulder_ik to the origin of coordinate axis.

17, Freeze Transformations for ctrl_shoulder_ik to zero the translation and rotation, Local Rotate Pivot and Local Scale Pivot also will be zeroed at the same time.

18, Then Match Translation from ctrl_shoulder_ik to ikjoint_shoulder again.

19, Match Pivots of shoulder controller to the IK joint. (Don’t foret to check Orientation)

At this example, pivots between shoulder controller and IK joint was matched before, but to be safe we should do it again.

20, Offset Parent Matrix the ctrl_shoulder_ik to clean transformation, the Offset Parent Matrix of shoulder IK joint had been cleaned before.