Construct Pivot-Slide Chain Tool — Python
The Construct Pivot-Slide Chain Tool creates an interpolation, pivot-slide chain from 6 button presses and 4 fields with a main control and three interpolation controls. The ease of construction supports iteration and flexibility when rigging.
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It starts by storing the positions of the start and end of its deformation chain from the User-set cursor location matching the model or reference, constructing an initial bone from the data. The User then inputs the desired names of the deformation bones, which the tool subdivides and names the deformation chain from. The User can then position each bone of the deformation chain to match their reference or model. Next, children bones are created on the deformation bone heads to be used as anchors for custom shape controls. Finally, the control and reverse chain are constructed from the deformation chain, involving positioning, hierarchy, constraints, drivers, and names. Also, a main control and three interpolation controls are constructed with constraints, a property linked to constraints, and names. The main control name is collected from a User-set field. Every bone created is assigned to a bone collection aligned with its naming convention prefix, designating its purpose.
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The design of the interpolation, pivot-slide chain is from Nathan Vegdahl's Humane Rigging course. I wrote documentation from their course, prototyped a rig in Blender 5.0.0 referencing it, and then constructed the tool in Python following my documentation. The largest function, construct_mechanical_chains() is 515 lines.
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Nathan Vegdahl, Humane Rigging, https://www.youtube.com/watch?v=3J-XN38EnhQ&list=PLE211C8C41F1AFBAB
Nathan Vegdahl's professional website, https://cessen.com/
Model used in implementation:
Yaroslav Lytvyn
https://3dexport.com/free-3dmodel-base-mesh-female-475312.htm
https://www.turbosquid.com/3d-models/female-base-mesh-2090546
Demonstration of the tool.
Functionality of the output.
Implementation of output interpolation, pivot-slide chain in a base mesh woman model performing a walk-cycle.
Implementation of output interpolation, pivot-slide chain in a base mesh woman model performing acrobatics.
Snippet of Python code creating the pivot-slide property on the main control and applying a linked driver to the reverse chain's constraints.
Snippet of Python code applying a copy transform constraint from each control bone to its respective deformation bone.
Addon hierarchy of the tool.
First page of the documentation for the interpolating pivot-slide chain written from Nathan Vegdahl's Humane Rigging course.
First page of the control chain documentation for the interpolation, pivot-slide chain written from Nathan Vegdahl's Humane Rigging course.