Maya Rigging – Gears and Chain with IK Spline Setup

Tutorial on Rigging Gears and  Chain using a IK Spline Setup..

This is the process I used for my Steampunk Car that I’m currently in the process of creating (will post images up soon)

I used the tutorial from  3D World Issue 154 ~ Create a robot and rig tank tracks   as a reference and tweaked the process to use bones and IK Spline Setup.

If there are parts that need more screenshots or clarification let me know.

Maya Rigging – Gears and Chain with IK Spline Setup

1. Create part of the chain geometry – duplicate it and then join together to create a chain
   
   
2. Select all geometry of each section and group them all
3. In top view add bone for every connection
   
   
4. Select Bones and the group node
5. Skin > Bind to Skin > Rigid Bind  — if move you move one of the bones it should move your chain geometry.
   (Edited: For Maya 2015 – Select the Bones and group node and open script editor (windows > General Editor > Script Editor type RigidBindSkin. press Ctrl Enter)
6. Create curve around gears for chain to follow
   
7. Skeleton > IK Spline handle > options – (use same settings as below)
   
8.  Select start joint than the end joint and the curve
9. The chain should snap around your curve. If your chain doesn’t complete your curve undo the IK Spline and bones and create more geometry and bones. The chain should snap around your curve. If your chain doesn’t complete your curve undo the IK Spline and bones and create more geometry and bones.
   
10.  Delete the IK Handle in the Outliner
    
11. This will disconnect the bones from the IK handle  but the geometry will still be in place.
12. Duplicate the ik curve and name it motion path
13. Skeleton > ik spline handle > options (use options below)
    
14. Select start joint then the end joint and the curve
15. It should snap into place again but this time in Outliner you will have a  transform group node if you select the node and move it, the chain and bones will follow
    
16. Using the transfer node we are going to connect it to the motion Path Curve
17. Select the transform nod and curve motion path go to  Animate > Motion Paths > Attached to Motion Paths Option — I used the options below.
    
18. scrub the timeline and it will move the chain around
19. Create two locators name them  BigGear and Small Gear
20. Select one of the gears and select one of the locators go to
21. constrain > point constrain  options reset
22. The locator should snap into the middle of the gear
23. Repeat for the other Gear
24. Both locators should be in the middle of the gears
    
25. Go into outliner and delete the Constraint
    
26. Select both locators and freeze transformations
27. Select the locator and corresponding gear
28. Constrain > Orient – ( you should be able to rotate the gear using the locator)
29. Repeat for other Gear
30. Create a Nurb Circle — Name is Gear_ctrl
31. Select Gear and select circle using the point constraint process as before
32. The circle should snap into place centre .  Delete the point constraint
33. Move, scale and rotate the circle away from the gear slightly so it’s in front and can be selected easily
    
34. Freeze transformations on the circle
35. In the motion path attribute properties break U Value connection
    
36. Select your IK Curve ( the curve that you used for the IK spline
37. Isolate it so that you have just the curve visible
38. Select all the vertices and go to  Create Deformers > Cluster
39. Do the same for the Motion Path curve
40. Parent Cluster 1 (IK Curve Cluster ) under Cluster 2 (motion Path Cluster)
41. Select Motion Path and go to Edit Curve >  Reverse Curve Direction  ( make sure in Surfaces Menu)
42. Open Hypershade ( Windows > Render Editors > Hypershade )
43. Select the Motion Path curve in the Outliner
44. Click the Input and Output connections button in the Hypershade 
45. All the connections of the curve should appear Select the MotionPathShape Node and move it away from the graph 
    
    
46. Create Curve Info node ( located under Utilities ) move it near Curve Shape Node
47. Select  Curveshape node middle mouse button drag onto curve info node and select other to bring up the connection Editor . Select WordSpace for Outputs and inputCurve for Inputs
    
48. Select the curveinfo node and open the attribute editor .. The arc Length is the length your curve. Make note of the digits
    
49. We are going to create Expression ( This expression is based on 3D world tutorial tweaked code so that it works with this setup ) .,. Change the Length of curve to length of your curve..
    (click image to enlarge)

    int $GearDirection; $GearSpeed = 200; float $GearRoateZ = Gear_ctrl.rotateZ; float $CurveLength = 178.359; if ($GearRoateZ < 0) { $GearDirection = -360; reverseCurve1.nodeState = 0; } else { $GearDirection = 360; reverseCurve1.nodeState = 1; } float $GearPos = ($GearRoateZ /(2 * 3.14 * $CurveLength)) * $GearDirection;motionPath1.uValue = ($GearPos % $GearSpeed)/$GearSpeed;

50. Select the Small Gear Locator and the Big Wheel Locator go to Constrain >  Orient
51. Select the Gear_ctrl  curve and Select Smaller Locator go to Constrain > Orient
52. If rotate Gear_ctrl  curve the gears and chain should rotate
53. If you notice that the gears are flipping or slipping
    How I fixed this was in motionPath attribute do below
    
54. Rotate the curve a bit so the U value changes.. and unclick follow.
55. Now if you rotate the circle it should work fine
56. Create Locator named Gears_Moveloc
57. Organize the scene like follows
    
58. Select both gear geometry and Ctrl + G  to group them.. name group Gears
59. Select the Gears_Moveloc locater and the Gear Group node and do Constrain  > Parent
60. Now you can move the whole rig with Gears_Moveloc