Maya API ramp attribute bug?

1. When saving:

2. What gets stored in the ascii file: 
setAttr -s 2 ".falloff[1]"  1 1 1;

3. After opening the scene again:

I recently noticed in Maya 2018 that custom Python API 1.0 node ramp attribute elements with position/value/interpolation : 0.0/0.0/linear do not get saved with the Maya scene (if their index is the lowest). I guess this is a bug. Some debug infos I gathered:
  • Probably bug source: By default Maya does not save attribute default values
  • Does not happen with default Maya nodes like remapValue
  • MPxNode.shouldSave documentation explains why this should not happen (but it is not true): "This method is not called for ramp attributes since they should always be written."
  • Since shouldSave gets wrongfully called it has to be overwritten to fix the problem
  • Only returning 'unknown' will not save the attribute. OpenMayaMPx.MPxNode.shouldSave(...) does exactly that.
  • The Python devkit example of shouldSave pyApiMeshShape.py is a bit misleading: From what I have tested all these return values seem to force save: True, False, None 

Implementations of this workaround can be found in prClosestPoint:


prPyMath.py making-of

A custom Maya node that can be found here:
Direct file link:

I wanted to create a node for some trigonometry functions, so I don't have to pollute the node graph with expressions. But after noticing that the functions I needed are all part of the Python math module I decided to just wrap the whole module, to make the node more useful.
There are only a few repeating argument in the whole module and all functions return one or two numbers. Which means there are also few Maya attributes needed to cover all cases.

A math node with that many operations is not typical for Maya.
When comparing such general purpose math nodes it might be better to just use a Python expression node like this one: http://around-the-corner.typepad.com/adn/2012/08/a-mathematical-dg-node.html

It was the first time I used the Maya Python API 2.0 for an MPxNode. But in this simple case it did not make a big difference. For the Attribute Editor buttons "Create element", "Delete element" I had to look into querying the node in the Attribute Editor context for the first time. Currently it is a workaround with a hidden textfield. I guess a global MEL variable might be the proper way to handle that?!

prClosestPoint.py making-of

A "new" Maya deformer that can be found here:
Direct file link:

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.

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. 

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.

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.

New github account

I recently started putting repositories on github:
The link is also in the sidebar

  • One central spot for all my public tools. Easier access, support (opposed to creativecrash / highend3d where I used to upload them)
  • Code samples when applying for jobs
  • Get feedback from / collaborate with community