prClosestPoint.py making-of

A "new" Maya deformer that can be found here:

https://github.com/parzival-roethlein/prmaya

Direct file link:

https://github.com/parzival-roethlein/prmaya/blob/master/prmaya/plugins/prClosestPoint.py

Origin
Initially I just wanted to update my old prAttractNode from 2011 to work in Maya 2016+, for which I only had to update the envelope, inputGeom, outputGeom attributes (MPxGeometryFilter instead of MPxDeformerNode). But then I also added new attributes and changed the existing ones to make it more user-friendly, scalable, functional:

• Added positions as target option 
• Set all target type attributes to arrays 
• Made all targets work simultaneously
• Added on/off switch attributes

So almost every attribute changed and was not backwards compatible. Which is why I ended up giving the node a new name, that is also more suitable for the algorithm.

Usability

In production I mostly used prAttractNode when modeling. For sticky lips only once or twice. But that might be because of the kind of stylized projects I usually work on. It could be much more useful for visual programming, but many nodes are still missing for that in Maya. Python is also too slow for that, unless the affected vertex count is small enough. 

Code

I would have liked to switch to the Python API 2.0, but the deformer proxy class has not been ported yet.

For the mesh input I switched from MMeshIntersector to MFnMesh, which is slower. I was having issues getting the matrix for MMeshIntersector to work. I used it in the past (see prAttractNode) so it might be a new bug, or I just made a mistake. On the upside it is more user friendly to not require the matrix input for mesh shapes.

Thoughts
The past ~5 years I haven't written any deformers with the Maya API. I mostly used it in Python scripts to improve performance and to use API exclusive features.
I find it strange that basic classes like MPxDeformerNode are still missing in the Maya Python API 2.0 after having tried it for the first time in early 2013.
A visual programming / procedural node option like Softimage ICE, Fabric Engine, Houdini would be a much better fit for most of my deformer needs. I was anticipating something similar for Maya in 2011, but after so many years and seeing what happend with Softimage and Fabric I have no idea if / when it will ever happen.
The verbose low level nature of C++ Maya deformers only seemed to have increased with the new MPxGPUDeformer class. I haven't really looked into it yet, but the devkit example MPxoffsetNode.cpp has ~600 lines of code for a simple one line vector offset algorithm. That seems quite far away from production problem solving and applied math that I would like to focus on when creating a deformer.