Quaternion Rotation Output from RBF Solvers
Feb 21, 2020 Maya Rigging Python C++ Maya API RBF Quaternions
In my previous post, I described how driving an RBF solver with quaternion values for rotational inputs is more reliable than driving with euler inputs. In this post, I will describe a method to output rotational values from an RBF solver. As described in my last post, euler rotations suffer from gimbal lock and multiple solutions to the same rotation. If we were to solve directly to these euler angles, we would see a lot of undesirable flipping depending on the sample inputs.

Quaternion Rotation Input to RBF Solvers
Feb 3, 2020 Maya Rigging Python C++ Maya API RBF Quaternions
In my previous post, I described how to create an RBF solver using regularized linear regression. While the solver works well for most independent input values, it does not work so well if we want to drive it with euler rotations. Euler rotations are susceptible to gimbal lock and can have multiple solutions for the same rotation. These two joints look like they have the same rotation. But looking at their animation curves tells a different story:

Regularized Linear Regression with Radial Basis Functions
Feb 2, 2020 Maya Rigging Python C++ Maya API RBF
RBF solvers are systems used to interpolate from values in one space to another set of values in another space. Basically a set driven key with arbitrary inputs and arbitrary outputs. This has many applications such as driving corrective shapes, retargeting meshes, or training systems in machine learning to predict values based on a set of known samples. There are several demo implementations and explanations of RBF solvers scattered around the internet:

Swing Twist Decomposition to Offset Parent Matrix
Jan 25, 2020 Maya Rigging Python C++ Maya API Maya
Decomposing a rotation into separate swing and twist components has many useful applications. Maya's pose interpolator toolset allows shapes to be driven with isolated twist and/or swing components of rotations. This allows a corrective shape in the pectorals driven by the raising of the arm to be independent from the twist motion of the arm. Also, the twist component can be used to drive twist joints more reliably than the euler twist axis by itself, as demonstrated in the video below.

Trig Functions in Maya without Third-Party Plug-ins
Jan 7, 2020 Maya Rigging Python
By default Maya does not ship with any nodes to calculate trig functions. If you want to use a plug-in, you can use the great plug-in Maya Math Nodes written by Serguei Kalentchouk. If you want or have to use default Maya, there is still hope. I recently added trig function support to dge, my library that converts string math equations to Maya node networks. Using math and trig knowledge, we can recreate these functions with the nodes that come with Maya.

Python Scripting for Maya Artists 2.0
Feb 28, 2016 Maya python
I've updated my semi-popular pages on Python Scripting for Maya Artists. The material was originally written in 2009 and the pdf has been downloaded over 18,000 time so it was all due for an update. Updates include: Various cleanup on examples and explanations. New material on string formatting. New material on directory traversal. New material on docstring formats. New section on code conventions and PEP8. New section on writing clean code.

Unit Testing in Maya (Part 2)
Feb 20, 2016 cmt Maya python unit testing
Edited: 6/18/2016: Updated RollbackImporter to support relative imports and “from package import module” syntax. In my last post, I went over writing scripts that can be used to write unit tests for Maya tools and then run those tests from the commandline outside of Maya. In this post, I'll go over running those tests interactively in Maya. Being able to run tests interactively in Maya will greatly speed up debug times when tracking down issues because you'll be able to see what is going on in your tests.

Unit Testing in Maya
Feb 15, 2016 cmt Maya python unit testing
Unit testing is a valuable tool that a lot of studios fail to implement. Unit testing can save a great amount of time and energy (and therefore money) by allowing developers, tool writers, and even content creators to catch broken deliverables before passing them downstream in the pipeline. The lack of unit testing with TD's is most likely due to one of the following: The person doesn't know what unit testing is.