Stumbling Toward 'Awesomeness'

A Technical Art Blog

Tuesday, October 25, 2016

Skin Save/Load Tool


Some had asked me to package the previous code together into a tool. I was reluctant because there were many situations where it just didn’t work. I made something to aid a discussion on the beta forum.

However, accidentally, I seem to have the code working. It’s odd, but the solution to skinClusters not being paintable after deformerWeights was used to load them was to try and make another skinCluster (which errors, but fixes the Artisan issue).

I have tossed this on GitHub here:


posted by Chris at 10:46 AM  

Monday, September 26, 2016

Save/Load SkinWeights 125x Faster

DISCLAIMER/WARNING: Trying to implement this in production I have found other items on top of the massive list that do not work. The ignore names flag ‘ig’ causes a hard crash on file load, the weight precision flag ‘wp’ isn’t implemented though it’s documented, the weight tolerance flag ‘wt’ causes files to hang indefinitely on load. When it does load weights properly, it often does so in a way that crashes the Paint Skin Weights tool. I have reported this in the Maya Beta forums.

Previously I discussed the promise in Maya command ‘deformerWeights‘. The tool that ships with Maya was not very useful, but the code it called was 125 times faster than python if you used it correctly..

Let’s make a python class that can save and load skin weights. You hand it a few hundred skinned meshes (avg Paragon character) and it saves the weights and then you delete history on the meshes, and it loads the weights back on.  What I just described is the process riggers go through when updating a rig or a mesh _every day_.

Below we begin the class, we import a python module to parse XML, and we say “if the user passed in a path, let’s parse it.”

#we import an xml parser that ships with python
import xml.etree.ElementTree
#this will be our class, which can take the path to a file on disk
class SkinDeformerWeights(object):
    def __init__(self, path=None):
        self.path = path
        if self.path:

Next, let’s make this parseFile function. Why is parsing the file important? In the last post we found out that there’s a bug that doesn’t appropriately apply saved weights unless you have a skinCluster with the *exact* same joints as were exported. We’re going to read the file and make a skinCluster that works.

#the function takes a path to the file we want to parse
def parseFile(self, path):
    root = xml.etree.ElementTree.parse(path).getroot()
    #set the header info
    for atype in root.findall('headerInfo'):
        self.fileName = atype.get('fileName')
    for atype in root.findall('weights'):
        jnt = atype.get('source')
        shape = atype.get('shape')
        clusterName = atype.get('deformer')

Now we’re getting some data here, we know that the format can save deformers for multiple shapes, let’s make a shape class and store these.

class SkinnedShape(object):
    def __init__(self, joints=None, shape=None, skin=None, verts=None):
        self.joints = joints
        self.shape = shape = skin
        self.verts = verts

Let’s use that when we parse the file, let’s then store the data we paresed in our new shape class:

#the function takes a path to the file we want to parse
def parseFile(self, path):
    root = xml.etree.ElementTree.parse(path).getroot()
    #set the header info
    for atype in root.findall('headerInfo'):
        self.fileName = atype.get('fileName')
    for atype in root.findall('weights'):
        jnt = atype.get('source')
        shape = atype.get('shape')
        clusterName = atype.get('deformer')
        if shape not in self.shapes.keys():
            self.shapes[shape] = self.skinnedShape(shape=shape, skin=clusterName, joints=[jnt])
            s = self.shapes[shape]

So now we have a dictionary of our shape classes, and each knows the shape, cluster name, and all influences. This is important because, if you read the previous post, the weights will only load onto a skinCluster with the exact same number and names of joints.
Now we write a method to apply the weight info we parsed:

def applyWeightInfo(self):
    for shape in self.shapes:
        #make a skincluster using the joints
        if cmds.objExists(shape):
            ss = self.shapes[shape]
            skinList = ss.joints
            cluster = cmds.skinCluster(, tsb=1)
            fname = self.path.split('\\')[-1]
            dir = self.path.replace(fname,'')
            cmds.deformerWeights(fname , path = dir,, im=1)

And there you go. Let’s also write a method to export/save the skinWeights from a list of meshes so we never have to use the Export DeformerWeights tool:

def saveWeightInfo(self, fpath, meshes, all=True):
    t1 = time.time()
    #get skin clusters
    meshDict = {}
    for mesh in meshes:
        sc = mel.eval('findRelatedSkinCluster '+mesh)
        #not using shape atm, mesh instead
        msh =  cmds.listRelatives(mesh, shapes=1)
        if sc != '':
            meshDict[sc] = mesh
            cmds.warning('>>>saveWeightInfo: ' + mesh + ' is not connected to a skinCluster!')
    fname = fpath.split('\\')[-1]
    dir = fpath.replace(fname,'')
    for skin in meshDict:
        cmds.deformerWeights(meshDict[skin] + '.skinWeights', path=dir, ex=1, deformer=skin)
    elapsed = time.time()-t1
    print 'Exported skinWeights for', len(meshes), 'meshes in', elapsed, 'seconds.'

You give this a folder and it’ll dump one file per skinCluster into that folder.
Here is the final class we’ve created [], and let’s give it a test run.

sdw = skinDeformerWeights()
>>>Exported skinWeights for 214 meshes in 2.433 seconds.

Let’s now load them back, we will iterate through the files in the directory and parse each, applying the weights:

import os
path = "e:\\gadget\\"
files = 0
for file in os.listdir(path):
    if file.endswith(".skinWeights"):
        fpath = path + file
        sdw = skinDeformerWeights(path=fpath)
        files += 1
elapsed = time.time() - t1
print 'Loaded skinWeights for', files, 'meshes in', elapsed, 'seconds.'
>>> Loaded skinWeights for 214 meshes in 8.432 seconds.

“>>> Loaded skinWeights for 214 meshes in 8.432 seconds.”

So that’s a simple 50 line wrapper to save and load skinWeights using the deformerWeights command. No longer do we need to write C++ API plugins to save/load weights quickly.

posted by Chris at 1:27 AM  

Saturday, September 24, 2016

DeformerWeights Command, Cloaked Savior?


This post was originally going to be entitled ‘Why Everyone Writes their Own Skin Exporter’. Maya’s smooth skin weight export tool hasn’t changed since Maya 4.0 when it was introduced 15 years ago. It saves out greyscale weightmaps in UV space, one image per joint influence per mesh. The only update they have done in 15 years is change the slider to go from a max of 1024 pixels to 4096, and now 8192!

Autodesk understands the need and importance of a skin weight exporter, they even ship it as a C++ example in their Maya Developer Kit / SDK. So why are they still shipping this abomination above?


Like blind data discussed before, in pythonland we cannot set skinweights in one go, we must iterate through the entire mesh setting skin weights one vertex at a time. This means a Maya feature or C++ plugin can save and load skin weights in seconds that take python 15 minutes.

I have written lots of skin weight save/load crap in my time, and as I sat down and started to do that very thing in an instructional blog post one night, we had an interesting discussion in the office the next day. ADSK added ‘Export Deformer Weights‘ in 2011, but it has never really worked. I don’t know a single person who uses it. But it does save and load ‘deformer’ weights via the C++ API –so there’s real promise here!



Save/load skin weights fast without writing a custom Maya plugin? This is kinda like the holy grail, which is ridiculous, but you should see the lengths people go to eek out a little more performance! My personal favorite was MacaroniKazoo back in 2010 reaching in and setting the skinCluster weight list directly by hand using an unholy conglomeration of python API and MEL commands. Tyler Thornock has a post that builds on this here.

So I asked the guys if anyone had looked at Export Deformer Weights recently, everyone either hadn’t heard of it, heard it was shit, or had some real first-hand experience of it being “A bit shit.” But still –the promise was there!

Export Deformer Weights: Broken and Backwards

So, first thing’s first, I made an awesome test case. I am going to go over all the gotchas and things that are broken, but if you don’t want to take this voyage of discovery, skip this section.


I open the deformer weight export tool, and just wow.. I mean the UI team really likes it’s space:


I save my skin weights to an XML file, delete history on the mesh, and open the import UI:


Gotcha 1) It requires a deformer to load weights onto. You need to re-skin your mesh.

I re-skinned my mesh and loaded the XML using Index.. drumroll..


Well, this is definitely not applying the weights back by vertex index. I decided to try ‘Nearest’:


Gotcha 2) Of the options [Index, Nearest, Over], ‘Index’ is somehow lossy, and anything other than ‘Index’ seems to crash often, ‘Nearest’ seems totally borked. (above)

So this was when I just began to think this was a complete waste of my time. I was pretty annoyed that they even shipped a tool like this, something that is so needed and so important, yet crashes frequently and completely trashes your data when it does work.


Not Taking ‘Broken and Backwards’ for an Answer

I am already invested and, not understanding how loading weights by point index could be lossy and broken, I decided to look at the XML file. The tool writes out one XML file per skinCluster, here’s a rundown of the file format:

Mesh Info (Shape) – the vertices of the shape are stored local space x,y,z and corresponding index

<?xml version="1.0"?>
  <headerInfo fileName="C:/Users/chris.evans/Desktop/test_sphere.xml" worldMatrix="1.000000 0.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 0.000000 1.000000 "/>
  <shape name="pSphereShape1" group="7" stride="3" size="382" max="382">
    <point index="0" value=" 0.148778 -0.987688 -0.048341"/>
    <point index="1" value=" 0.126558 -0.987688 -0.091950"/>
    <point index="2" value=" 0.091950 -0.987688 -0.126558"/>

Joints (Weights) – There is one block per joint that calls out each vertex that it have influences for on the shape

  <weights deformer="skinCluster1" source="root" shape="pSphereShape1" layer="0" defaultValue="0.000" size="201" max="380">
    <point index="0" value="0.503"/>
    <point index="1" value="0.503"/>
    <point index="2" value="0.503"/>

And that’s it, not a lot of data, nothing about the skinCluster attributes or options, no support for spaces like UV or world. (odd, since it’s had UV support for 15 years)

Next I decided to run the tool again and see what command it was calling, I then looked up the command documentation and here’s where it gets interesting, go ahead, take a look!


So now I am hooked, someone is putting some thought into this –at least on some level.


I don’t at all understand why the UI has none of these options, but I need to get this working. If you read through the docs, the command also supports:

  • Exporting multiple skinClusters/shapes/deformers per XML file
  • Exporting skinCluster/deformer attributes like ‘skinningMethod’ and ‘envelope’
  • Local and world space positions with a positional tolerance

“Someone is putting some thought into this”

So I started trying to figure out why a file format that explicitly knows every influence of every vertex by index and inf name, doesn’t load weights properly. After some trials I hit gotcha #3:

Gotcha 3) Of the options the weights only load properly if the skinCluster has the *exact* same influences it was saved with. Which really makes no sense, because the file format has the name of every joint in the old skinCluster.

So now I had it working, time to wrap it and make it useful.

The Documentation is a Lie.

So, first thing’s first, I did a speed test.

Importing with deformerWeights was about 125 times faster: Gold mine.

But I just couldn’t get some of the flags to work, I thought I was just a moron, until I finally tried the code example in the ADSK Maya documentation, which FAILS. Let’s first look at the -vc flag, which is required to load using ‘bilinear’ or ‘barycentric’ mapping/extrapolation:

cmds.deformerWeights ("testWeights.xml", ex=True, vc=True, deformer="skinCluster1")
# Error: Invalid flag 'vc'
# Traceback (most recent call last):
#   File "<maya console>", line 1, in <module>
# TypeError: Invalid flag 'vc' #

Gotcha 4) The python examples do not work. -vertexConnections flag doesn’t work, -attribute flag doesn’t work, so no saving skincluster metadata like ‘skinningMethod’, etc. Because of that, ‘barycentric’ and other methods that need vertex connection info do not work. The ‘deformer’ flag shows that it takes a list of deformers and writes them all to one file, but this is not true, it takes a single string name of a deformer.

I now know why the UI doesn’t have all these cool options! –they don’t work!

Gotcha 5) It doesn’t take a file path, to save a file to a path you need to specify the filename, and then the path separate.

cmds.deformerWeights ("testWeights.xml", path='d:\\myWeight\\export\\folder\\', ex=True, deformer="skinCluster1")

Perhaps someone fixed this stuff, documented it, and then reverted the fix, but this has been around since 2011.. I tried the above in maya 2016 latest service pack and all my links above are to that version of the documentation.

I wasn’t really intending to write this much, so now that we know this can import weights 125 times faster, we’ll make a tool to utilize it. Stay tuned!

posted by Chris at 2:15 AM  

Friday, October 17, 2014

Embedding Icons and Images In Python with XPM


As technically-inclined artists, we often like to create polished UIs, but we have to balance this with not wanting to complicate the user experience (fewer files the better). I tend to not use too many icons with my tools, and my Maya tools often just steal existing icons from Maya: because I know they will be there.

However, you can embed bitmap icons into your PySide/PyQt apps by using the XPM file format, and storing it as a string array. Often I will just place images at the bottom of the file, this keeps icons inside your actual tool, and you don’t need to distribute multiple files or link to external resources.

Here’s an example XPM file:

/* XPM */
static char *heart_xpm[] = {
/* width height num_colors chars_per_pixel */
"7 6 2 1",
/* colors */
"` c None",
". c #e2385a",
/* pixels */

This is a small heart, you can actually see it, in the header you se the ‘.’ maps to pink, you can see the ‘.’ pattern of a heart. The XPM format is like C, the comments tell you what each block does.
Here’s an example in PySide that generates the above button with heart icon:

import sys
from PySide import QtGui, QtCore
def main():
    app = QtGui.QApplication(sys.argv)
    heartXPM = ['7 6 2 1','N c None','. c #e2385a','N..N..N',\
    w = QtGui.QWidget()
    w.setWindowTitle('XPM Test')
    w.button = QtGui.QPushButton('XPM Bitmaps', w)
if __name__ == '__main__':

You need to feed QT a string array, and strip everything out. Gimp can save XPM, but you can also load an image into xnView and save as XPM.

Addendum: Robert pointed out in the comments that pyrcc4, a tool that ships with PyQt4, can compile .qrc files into python files that can be imported. I haven’t tried, but if they can be imported, and are .py files, I guess they can be embedded as well. He also mentioned base64 encoding bitmap images into strings and parsing them. Both these solutions could really make your files much larger than XPM though.

posted by Chris at 3:23 PM  

Thursday, October 16, 2014

Tracing and Visualizing Driven-Key Relationships


Before I get into the collosal mess that is setting driven keys in Maya, let me start off by saying, when I first made an ‘SDK’ in college, back in 1999, never did I think I would still be rigging like this 15 years later. (Nor did I know that I was setting a ‘driven key’, or a ‘DK’ which sounds less glamorous)

How The Mess is Made


Grab this sample scene [driven_test]. In the file, a single locator with two attributes drives the translation and rotation of two other locators. Can’t get much ismpler than that, but look at this spaghetti mess above! This simple driven relationship created 24 curves, 12 blendWeighted nodes, and 18 unitConversion nodes. So let’s start to take apart this mess. When you set a driven-key relationship, it uses an input and a curve to drive another attribute:


When you have multiple attributes driving a node, maya creates ‘blendWeighted’ nodes, this blends the driven inputs to one scalar output, as you see with the translateX below:


Blending scalars is fairly straight forward, but for rotations, get ready for this craziness: A blendWeighted node cannot take the output of an animCurveUA (angle output), the value must first be converted to radians, then blended. But the final node cannot take radians, so the result must be converted back to an euler angle. This happens for each channel.


If you think this is retarded; welcome to the club. It is a very cool usage of general purpose nodes in Maya, but you wouldn’t think so much of rigging was built on that, would you? That when you create a driven-key it basically makes a bunch of nodes and doesn’t track an actual relationship, because of this, you can’t even reload a relationship into the SDK tool later to edit! (unless you traverse the spaghetti or takes notes or something)

I am in love with Node Edtor, but by default hypergraph did hide some of the spaghetti, it used to hide unitConversions as ‘auxiliary nodes’:


Node Editor shows unitConversions regardless of whether aux nodes are enabled, I would rather see too much and know what’s going on than have things hidden, but maybe that’s just me. You can actually define what nodes are considered aux nodes and whether ‘editors’ show them, but I am way off on a tangent here.

So just go in there and delete the unit conversion yourself and wire the euler angle output, which you would think is a float.. into the blendWeighted input, which takes floats. Maya won’t let you, it creates the unitConversion for you because animCurveUA outputs angles, not floats.

This is why our very simple example file generated over 50 nodes. On Ryse, Maruis’ face has about 73,000 nodes of driven-key spaghetti. (47,382 curves,  1,420 blendWeighted, 24,074 unitConversion)

Finding and traversing

So how do we find this stuff and maybe query and deal with it? Does Maya have some built in way of querying a driven relationship? No. Not that I have ever found. You must become one with the spaghetti! setDrivenKeyframe has a query mode, but that only tells you what ‘driver’ or ‘driven’ nodes/attrs are in the SDK window if it’s open, they don’t query driver or driven relationships!

We know that these intermediate nodes that store the keys are curves, but they’re a special kind of curve, one that doesn’t take time as an input. Here’s how to search for those:

print len("animCurveUL","animCurveUU","animCurveUA","animCurveUT")))

So what are these nodes? I mentioned above that animCurveUA puts out an angle:

  • animCurveUU – curve that takes a double precision float and has a double output
  • animCurveUA – takes a double and outputs an angle
  • animCurveUL – takes a double and outputs a distance (length)
  • animCurveUT – takes a double and outputs a time

When working with lots of driven-key relationships you frequently want to know what is driving what, and this can be very difficult because of all the intermediate node-spaghetti. Here’s what you often want to know:

  • What attribute is driving what – for instance, select all nodes an attr drives, so that you can add them back to the SDK tool. ugh.
  • What is being driven by an attribute

I wrote a small script/hack to query these relationships, you can grab it here [drivenKeyVisualizer]. Seriously, this is just a UI front end to a 100 line script snippet, don’t let the awesomeness of QT fool you.


The way I decided to go about it was:

  1. Find the driven-key curves
  2. Create a tiny curve class to store little ‘sdk’ objects
  3. List incoming connections (listConnections) to get the driving attr
  4. Get the future DG history as a list and reverse it (listHistory(future=1).reverse())
  5. Walk the reversed history until I hit a unitConversion or blendWeighted node
  6. Get it’s outgoing connection (listConnections) to find the plug that it’s driving
  7. Store all this as my sdk objects
  8. Loop across all my objects and generate the QTreeWidget

Here’s how I traversed that future history (in the file above):

 #search down the dag for all future nodes
 futureNodes = [node for node in cmds.listHistory(c, future=1, ac=1)]
 #reverse the list order so that you get farthest first
 drivenAttr = None
 #walk the list until you find either a unitConversion, blendWeighted, or nothing
 for node in futureNodes:
     if cmds.nodeType(node) == 'unitConversion':
             drivenAttr = cmds.listConnections(node + '.output', p=1)[0]
             cmds.warning('blendWeighted node with no output: ' + node)
     elif cmds.nodeType(node) == 'blendWeighted':
             drivenAttr = cmds.listConnections(node + '.output', p=1)[0]
             cmds.warning('blendWeighted node with no output: ' + node)
 if not drivenAttr:
     drivenAttr = cmds.listConnections(c + '.output', p=1)[0]
 if drivenAttr:
     dk.drivenAttr = drivenAttr
     cmds.warning('No driven attr found for ' + c)

This of course won’t work if you have anything like ‘contextual rigging’ that checks the value of an attr and then uses it to blend between two banks of driven-keys, but because this is all general DG nodes, as soon as you enter nodes by hand, it’s no longer really a vanilla driven-key relationship that’s been set.

If you have a better idea, let me know, this above is just a way I have done it that has been robust, but again, I mainly drive transforms.

 What can you do?

Prune Unused Pasta


Pruned version of the DAG

By definition, when rigging something with many driven transforms like a face, you are creating driven-key relationships based on what you MIGHT need. This goes for when making the initial relationship, or in the future when you maybe want to add detail. WILL I NEED to maybe translate an eyelid xform to get a driven pose I want.. MAYBE.. so you find yourself keying rot/trans on *EVERYTHING*. That’s what I did in my example, and the way the Maya SDK tool works, you can’t really choose which attrs per driven node you want to drive, so best to ‘go hunting with a shotgun’ as we say. (shoot all the trees and hope something falls out)

Ok so let’s write some code to identify and prune driven relationships we didn’t use.

CAUTION: I would only ever do this in a ‘publish’ step, where you take your final rig and delete crap to make it faster (or break it) for animators. Also, I have never used this exact code below in production, I just created it while making this blog post as an example. I have run it on some of our production rigs and haven’t noticed anything terrible, but I also haven’t really looked. 😀

def deleteUnusedDriverCurves():
    for driverCurve in"animCurveUL","animCurveUU","animCurveUA","animCurveUT")):
        #delete unused driven curves
        if not [item for item in cmds.keyframe(driverCurve, valueChange=1, q=1) if abs(item) &gt; 0.0]:

This deletes any curves that do not have a change in value. You could have multiple keys, but if there’s no curve, let’s get rid of it. Now that we have deleted some curves, we have some blendWeighted nodes that now aren’t blending anything and unitConversions that are worthless creatures. Let’s take care of them:

def deleteUnusedBlendNodes():
    #rewire blend nodes that aren't blending anything
    for blendNode in'blendWeighted'):
        if len(cmds.listConnections(blendNode, destination=0)) == 1:
            curveOutput = None
            drivenInput = None
            #leap over the unitConversion if it exists and find the driving curve
            curveOutput = cmds.listConnections(blendNode, destination=0, plugs=1, skipConversionNodes=1)[0]
            #leap over the downstream unitConversion if it exists
            conns = cmds.listConnections(blendNode, source=0, plugs=1, skipConversionNodes=1)
            for conn in conns:
                if cmds.nodeType(conn.split('.')[0]) == 'hyperLayout': conns.pop(conns.index(conn))
            if len(conns) == 1:
                drivenInput = conns[0]
                cmds.warning('BlendWeighted had more than two outputs? Node: ' + blendNode)
            #connect the values, delete the blendWeighted
            cmds.connectAttr(curveOutput, drivenInput, force=1)
            print 'Removed', blendNode, 'and wired', curveOutput, 'to', drivenInput

We find all blendWeighted nodes with only one input, then traverse out from them and directly connect whatever it was the node was blending, then we delete it. This is a bit tricky and I still think I may have missed something because I wrote this example at 2am, but I ran it on some rigs and haven’t seen an issue.

Here are the results running this code on an example rig:


Create a Tool To Track / Mirror / Select Driven Relationships

This is a prototype I was working on at home but shelved, I would like to pick it up again when I have some time, or would be open to tossing it on github if people would like to help. It’s not rocket science, it’s besically what Maya should have by default. You just want to track the relationships you make, and also select all nodes driven by an attr. Also mirror their transforms across an axis (more geared toward driven transforms).


Write Your Own Driver Node

Many places create their own ‘driven node’ that just stores driven relationships. Judd Simantov showed a Maya node that was used on Uncharted2 to store all facial poses/driven relationships:


The benefits of making your own node are not just in DAG readability, check out the time spent evaluating all these unitConversion and blendWeighted nodes in a complex facial rig (using the new Maya 2015 EXT 1 Profiler tool) –that’s over 760ms! (click to enlarge)


Though it’s not enough to make a node like this, you need to make a front end to manage it, here’s the front end for this node:


Give Autodesk Feedback!


As the PSD request is ‘under review’, maybe when they make the driver, they can make a more general framework to drive things in Maya.


As you can see, there are many ways to try to manage and contain the mess generated by creating driven-key relationships.  I would like to update this based on feedback, it’s definitely not an overview, and speaks more to people who have been creating driven-key relationships for quite some time.  Also, if you would find a tool like my Maya SDK replacement useful, let me know, especially if you would like to help iron it out and/or test it.

posted by Chris at 3:16 PM  

Wednesday, October 15, 2014

Reminder: Maya saves ScriptEditor tabs on crash


This is just a reminder that for some time now Maya has been saving all ScriptEditor tabs on crash. I frequently bump into people who don’t know or don’t remember this. If your Maya says that it’s attempting to save in your /Temp folder, it’s also saving all your ScriptEditor tabs.

posted by Chris at 11:56 AM  

Wednesday, September 24, 2014

Maya DAG nodes in QT tools (don’t use string paths)



String paths to Maya objects are _fragile_. This data is stale as soon as you receive it, long paths are better than short, and taking into account namespaces is even better –BUT when it comes down to it, the data is just old as soon as you get it, and there is a better way.

A Full Path that is Never Stale

If you store a node in a Maya Python API MDagPath object, you can ask at any time and get its full path. Because it’s basically a pointer to the object in memory. Here’s an example:

import maya.OpenMaya as om
#create and populate an MSelectionList
sel = om.MSelectionList()
#create and fill an MDagPath
mdag = om.MDagPath()
sel.getDagPath(0, mdag)
#At any time request the current fullpath to the node
print mdag.fullPathName()

CHALLENGE: Can you write a renaming tool that doesn’t use string path node representation? That works with all DG nodes? Without using PyMel? 😉

Embedding Maya Python Objects in PyQT (UserRole)

So.. if we can store a pointer to an object, how do we track that with QT UIs, pass it around, etc? It can be really difficult to find a way to be responsible here, you have all these lists and node representations, and in the past I would try to sync lists of python MDagPath objects, or make a dictionary that mirrors the listView… but there is a way to store arbitrary python objects on list and tree widgetitems!

In this code snipet, I traverse a selection and add all selected nodes to a list, I add ‘UserRole’ data to each and set that data to be an MDagPath:

    listWids = []
    for item in nodes:
        sel = om.MSelectionList()
        mdag = om.MDagPath()
        sel.getDagPath(0, mdag)
        name = mdag.fullPathName()
        if not self.longNamesCHK.isChecked():
            name = name.split('|')[-1]
        wid = QtGui.QListWidgetItem(listWid)
        wid.setData(QtCore.Qt.UserRole, mdag)

Now, later when we want to get the full path name of this widgetItem, we just ask it for this data. That returns the MDagPath object, and we can ask the object for the current full path to the node:

print self.drivenNodeLST.currentItem().data(QtCore.Qt.UserRole).fullPathName()

So this is a good way to have arbitrary data that travels wit the QT node description, which is usually some kind of widget.

posted by Chris at 12:40 PM  

Tuesday, May 27, 2014

PyQt: Composite Widgets


So the past few nights I was racking my brain a bit to get multiple widgets adding to a listview. I wanted to see a list of animations, each item in the list needed to have clickable buttons, and special labels.

I scoured the internets, and dusted off my old trusty ‘Rapid GUI Programming with Python and QT‘ book, I got the idea for the above from the ‘Composite Widgets’ chapter subsection, though they don’t use setItemWidget to insert a composite widget into another widget.

Here is what my QtDesigner file looked like:


I wanted to dynamically load a UI file of a custom widget and compile it with the UIC module. I first looked at making a delegate, but I just could not get that working, if you have done this with a delegate, let me know in the comments! (From the docs, it seems delegates cannot be composites of multiple widgets)

In the end I used pyuic4 to compile the above UI file into a python code, I dumped this, minus the form/window code, into a class I derive from QWidget:

class animItemWidget(QtGui.QWidget):
    def __init__(self, parent=None):
        super(animItemWidget, self).__init__()
        self.horizontalLayout_4 = QtGui.QHBoxLayout(self)
        #blah, blah, blah

At the bottom of that length UI frenzy of an init, let’s connect a button to a function:

self.connect(self.button02, QtCore.SIGNAL("clicked()"), self.awesome)

Now define that function, let’s just print that the animation that the widget in the list whose button you clicked is AWESOME:

    def awesome(self):
        print self.label.text() + ' is awesome!'

This could do anything with the anim name or various data bound to this object, like check out/sync a file from Perforce, load a file in Maya, etc.

Now let’s make our main window. We are going to use setItemWidget to insert our animItemWidget into the QListWidget called ‘list’. Notice that I have access to every UI element in the composite widget.

from PyQt4 import QtGui, QtCore, uic
class uiControlTest(QtGui.QMainWindow):
    def __init__(self):
        super(uiControlTest, self).__init__()
        self.ui = uic.loadUi('uiControlTest.ui')
        for i in range(0,100):
            wid = animItemWidget()
            wid.label_2.setText('Last edited by chrise @2014.06.21:23:17')
            wid.label.setText('Animation ' + str(i))
            wid2 = QtGui.QListWidgetItem()
            wid2.setSizeHint(QtCore.QSize(100, 40))
            self.ui.list.setItemWidget(wid2, wid)

Now, of course, in my example I just quickly made a bunch of widgets, so their names are all default, but you get the idea. If you have a better way to do this, perhaps something more performant, please let me know in the comments.

Note: It looks like that book is freely available on a college class website, save yourself 50 bucks:

posted by Chris at 2:38 AM  

Sunday, May 11, 2014

Maya: Vector Math by Example


This post is about how to use vector math and trigonometric functions in Maya, it is not a linear algebra or vector math course, it should give you what you need to follow along in Maya while you learn with online materials. Kahn Academy is a great online learning resource for math, and Mathematics for Computer Graphics, and Linear Algebra and its Applications are very good books. Gilbert Strang, the Author of Linear Algebra, has his entire MIT Linear Algebra course lectures here in video form. Also, Volume 2 of Complete Maya Programming has some vector math examples in MEL and C++.



Think of the white vector above as a movement. It does have three scalar values (ax, ay, az), sure, but do not think of a vector as a point or a position. When you see a vector, I believe it helps to imagine it as a movement from 0,0,0 – an origin. We don’t know where it started, we only know the movement.

A vector has been normalized, or is considered a unit vector, when it’s length is one. This is achieved by dividing each component by the length.


There are many Python libraries dedicated to vector math, but none ship with Python itself. I have tried numPy, then pyEuclid, and finally piMath. It can definitely be a benefit to load the same vector class across multiple apps like Maya, MotionBuilder, etc.. But, I used those in a time when MotionBuilder had no vector class, and before Maya had the API. Today, I use the vector class built into the Maya Python API (2.0), which wraps the underlying Maya C++ code: MVector

I had to call out 2.0 above, as those of you using the old API, you have to ‘cast’ your vectors to/from, meaning that classes like MVector (Maya’s vector class) don’t accept python objects like lists or tuples, this is still the case with the 2014 SWIG implementation of the default API, but not API 2.0. One solution is to override the MVector class in a way that it accepts a Python lists and tuples, essentially automatically casting it for you:

class MVector(om.MVector):
    def __init__(self, *args):
        if( issubclass, args, list ) and len(args[0])== 3:
            om.MVector.__init__(self, args[0][0], args[0][1], args[0][2])
            om.MVector.__init__(self, args)

But that aside, just use Maya Python API 2.0:

#import API 2.0
import maya.api.OpenMaya as om
#import old API
import maya.OpenMaya as om_old



Let’s first create two cubes, and move them

import maya.cmds as cmds
import maya.api.OpenMaya as om
cube1, cube2 = cmds.polyCube()[0], cmds.polyCube()[0]
cmds.xform(cube2, t=(1,2,3))
cmds.xform(cube1, t=(3,5,2))

Let’s get the translation of each, and store those as MVectors

t1, t2 = cmds.xform(cube1, t=1, q=1), cmds.xform(cube2, t=1, q=1)
print t1,t2
v1, v2 = om.MVector(t1), om.MVector(t2)
print v1, v2

This will return the translation in the form [x, y, z], and also the MVector, which will print: (x, y, z), and in the old API: <__main__.MVector; proxy of <Swig Object of type ‘MVector *’ at 0x000000002941D2D0> >. This is a SWIG wrapped C++ object, API 2.0 prints the vector.

Note: I just told you to think of vectors as a movement, and not as a position, and the first example I give stores translation in a vector. Maybe not the best, but remember this translation, is really being stored as a movement in space from an origin.

So let’s start doing stuff and things.


We have two translations, both stored as vectors, let’s get the distance between them, to do this, we want to make a new vector that describes a ray from one location to the other and then find it’s length, or magnitude. To do this we subtract each component of v1 from v2:

v = v2-v1
print v

This results in ‘-2.0 -3.0 1.0’.

To get the length of the vector we actually get the square root of the sum of x,y,and z squared sqrt(x^2+y^2+z^2), but as we haven’t covered the math module yet, let’s just ask the MVector for the ‘length’:

print om.MVector(v2-v1).length()

This will return 3.74165738677, which, if you snap a measure tool on the cubes, you can verify:


Use Case: Distance Check

As every joint in a hierarchy is in it’s parent space, a joint’s ‘magnitude’ is it’s length. Let’s create a lot of joints, then select them by joint length.

import maya.cmds as cmds
import random as r
import maya.api.OpenMaya as om
root = cmds.joint()
jnts = []
for i in range(0, 2000):
    jnt = cmds.joint()
    trans = (r.randrange(-100,100), r.randrange(-100,100), r.randrange(-100,100))
    cmds.xform(jnt, t=trans)
cmds.parent(jnts, root)


So we’ve created this cloud of joints, but let’s just select those joints with a joint length of less than 50.

sel = []
for jnt in jnts:
    v = om.MVector(cmds.xform(jnt, t=1, q=1))
    if v.length() < 50: sel.append(jnt)



The dot product is a scalar value obtained by performing a specific operation on two vector components. This doesn’t make much sense, so I will tell you that the dot product is extremely useful in finding the angle between two vectors, or checking which general direction something is pointing.

dot = v1*v2
print dot

USE CASE: Direction Test


The dot product of two normalized vectors will always be between -1.0 and 1.0, if the dot product is greater than zero, the vectors are pointing in the same general direction, zero means they are perpendicular, less than zero means opposite directions. So let’s loop through our joints and select those that are facing the x direction:

sel = []
for jnt in jnts:
    v = om.MVector(cmds.xform(jnt, t=1, q=1)).normal()
    dot = v*om.MVector([1,0,0])
    if dot > 0.7: sel.append(jnt)

USE CASE: Test World Colinearity

This one comes from last week in the office, one of my guys wanted to know how to check which way in the world something was facing. I believe it was to derive some information from arbitrary skeletons. This builds on the above by getting each vector of a node in world space.

def getLocalVecToWorldSpace(node, vec=om.MVector.kXaxisVector):
    matrix = om.MGlobal.getSelectionListByName(node).getDagPath(0).inclusiveMatrix()
    vec = (vec * matrix).normal()
    return vec
def axisVectorColinearity(node, vec):
    vec = om.MVector(vec)
    x = getLocalVecToWorldSpace(node, vec=om.MVector.kXaxisVector)
    y = getLocalVecToWorldSpace(node, vec=om.MVector.kYaxisVector)
    z = getLocalVecToWorldSpace(node, vec=om.MVector.kZaxisVector)
    #return the dot products
    return {'x': vec*x, 'y':vec*y, 'z':vec*z}
jnt = cmds.joint()
print axisVectorColinearity(jnt, [0,0,1])

You can rotate the joint around and you will see which axis is most closely pointing to the world space vector you have given as an input.

USE CASE: Angle Between Vectors


When working with unit vectors, we can get the arc cosine of a dot product to derive the angle between the two vectors, but this requires trigonometric functions, which are not available in our vector class, for this we must import the math module. Scratching the code above, let’s find the angle between two joints:

import maya.cmds as cmds
import maya.api.OpenMaya as om
import math
jnt1 = cmds.joint()
jnt2 = cmds.joint()
cmds.xform(jnt2, t=(0,0,10))
cmds.xform(jnt1, t=(10,0,0))
root = cmds.joint()
cmds.parent([jnt1, jnt2], root)
v1 = om.MVector(cmds.xform(jnt1, t=1, q=1)).normal()
v2 = om.MVector(cmds.xform(jnt2, t=1, q=1)).normal()
dot = v1*v2
print dot
print math.acos(dot)
print math.acos(dot) * 180 / math.pi

So at the end here, the arc Cosine of the dot product returns the angle in radians (1.57079632679), which we convert to degrees by multiplying it by 180 and dividing by pi (90.0). To check your work, there is no angle tool in Maya, but you can create a circle shape and set the sweep degrees to your result.

Now that you know how to convert radians to an angle, if you store the result of the above in an MAngle class, you can ask for it however you like:

print om.MAngle(math.acos(dot)).asDegrees()

Now that you know how to do this, there is an even easier, using the angle function of the MVector class, you can ask it the angle given a second vector:

print v1.angle(v2)

There are also useful attributes v1.rotateBy(r,r,r) for an offset and v1.rotateTo(v2). I say (r,r,r) in my example, but the rotateBy attr takes angles or radians.

CHALLENGE: Can you write your own rad_to_deg and deg_to_rad utility methods?

USE CASE: Orient-Driver

Moving along, let’s apply these concepts to something more interesting. Let’s drive a blendshape based on orientation of a joint. Since the dot product is a scalar value, we can pipe this right into a blendshape, when the dot product is 1.0, we know that the orientations match, when it’s 0, we know they are perpendicular.


We will use a locator constrained to the child to help in deriving a vector. The fourByFourMatrix stores the original position of the locator. I tried using the holdMatrix node, which should store a cached version of the original locator matrix, but it kept updating. (?) We use the vectorProduct node in ‘dot product’ mode to get the dot product of the original vector and the current vector of the joint. We then pipe this value into the weight of the blendshape node.

Now, this simple example doesn’t take twist into account, and we aren’t setting a falloff or cone, the falloff will be 1.0 when the vectors align and the blendshape is on 100% and 0.0, when they’re perpendicular and the blendshape will be on 0%. I also don’t clamp the dot product, so the blendshape input can go to -1.


The cross product results in a vector that is perpendicular to two vectors. Generally you would do (v1.y*v2.z-v1.z*v2.y, v1.z*v2.x-v1.x*v2.z, v1.x*v2.y-v1.y*v2.x), ut luckily, the vector class manages this for us by using the ‘^’ symbol:

cross = v1^v2
print cross

USE CASE: Building a coordinate frame


If we get the cross product of v1^v2 above, and use this vector to now cross (v1 x v2)x v1, we will now have a third perpendicular vector to build a coordinate system or ‘orthonormal basis’. A useful example would be aligning a node to a nurbs curve using the pointOnCurveInfo node.


In the example above, we are using two cross products to build a matrix from the tangent of the pointOnCurveInfo and it’s position, then decomposing this matrix to set the orientation and position of a locator.

Many people put content like this behind a paywall.
If you found this useful, please consider buying me a beer.

posted by Chris at 11:49 PM  

Monday, June 10, 2013

WordPress Malware Massacre


Some of my friends alerted me to my site being listed in the google malware database a week ago, but I was focusing on E3 and hadn’t had time to look into it. As it turns out, a vulnerability in a wordpress theme that I didn’t even have active allowed a virus to completely hose all sites on my co-located server with spam and random shit.

I wrote a quick python script [] that looks over all files and directories on linux and reports the following:

  • Html infested with twitter iFrame code injection
  • Malicious PHP, and code injected into existing PHP that eval’s strings obfuscated in
    • base_64
    • gzip
    • rot13
  • .htaccess files that change mod_rewrite.c to re-direct your users to bogus sites and internal php files
  • Files with permissions set greater than 664 and folders greater than 755
  • Hidden directories

I wrote this this afternoon and it’s focused on only this specific wordpress malware, it’s just basically some example code that warns of the above, and has two methods to remove PHP and HTML code injections.  Feel free to ask me questions, use at your own risk, by default the fixer methods are commented out, so this only reports issues. With them uncommented; they do make file edits to fix the code injections.

posted by Chris at 1:56 AM  

Monday, February 11, 2013

Object Oriented Python in Maya Pt. 1

I have written many tools at different companies, I taught myself, and don’t have a CS degree. I enjoy shot-sculpting, skinning, and have been known to tweak parameters of on-screen visuals for hours; I don’t consider myself a ‘coder’; still can’t allocate my own memory.  I feel I haven’t really used OOP from an architecture standpoint. So I bought an OOP book, and set out on a journey of self improvement.

‘OOP’ In Maya

In Maya, you often use DG nodes as ‘objects’. At Crytek we have our own modular nodes that create meta-frameworks encapsulating the character pipeline at multiple levels (characters, characterParts, and rigParts). Without knowing it, we were using Object Oriented Analysis when designing our frameworks, and even had some charts that look quite a bit like UML. DG node networks are connected often with message nodes, this is akin to a pointer to the object in memory, whereas with a python ‘object’ I felt it could always easily lose it’s mapping to the scene.

It is possible now with the OpenMaya C++ API to store a pointer to the DG node in memory and just request the full dag path any time you want it, also PyMel objects are Python classes and link to the DG node even when the string name changes.

“John is 47 Years Old and 6 Feet Tall”

Classes always seemed great for times when I had a bunch of data objects, the classic uses are books in a library, or customers: John is 47 years old and likes the color purple. Awesome. However, in Maya, all our data is in nodes already, and those nodes have attributes, those attributes serialize into a Maya file when I save: so I never really felt the need to use classes.

Although, all this ‘getting’, ‘setting’ and ‘listing’ really grows tiresome, even when you have custom methods to do it fairly easily.

It was difficult to find any really useful examples of OOP with classes in Maya. Most of our code is for ‘constructing’: building a rig, building a window, etc. Code that runs in a linear fashion and does ‘stuff’. There’s no huge architecture, the architecture is Maya itself.

Class Warfare

I wanted to package my information in classes and pass that back and forth in a more elegant way –at all times, not just while constructing things. So for classes to be useful to me, I needed them to synchronously exist with DG nodes.

I also didn’t want to have to get and set the information when syncing the classes with DG nodes, that kind of defeats the purpose of Python classes IMO.

Any time I opened a tool I would ‘wrap’ DG nodes in classes that harnessed the power of Python and OOP. To do this meant diving into more of the deep end, but since that was what was useful to me, that’s what I want to talk about here.

To demonstrate, let’s construct this example:

#the setup
loc = cmds.spaceLocator()
cons = [[0],[0]]
meshes = [cmds.sphere()[0], cmds.sphere()[0], cmds.sphere()[0]]
cmds.addAttr(loc, sn='controllers', at='message')
cmds.addAttr(cons, sn='rigging', at='message')
for con in cons: cmds.connectAttr(loc[0] + '.controllers', con + '.rigging')
cmds.addAttr(loc, sn='rendermeshes', at='message')
cmds.addAttr(meshes, sn='rendermesh', at='message')
for mesh in meshes: cmds.connectAttr(loc[0] + '.rendermeshes', mesh + '.rendermesh')

So now we have this little node network:


Now if I wanted to wrap this network in a class. We are going to use @property to give us the functionality of an attribute, but really a method that runs to return us a value (from the DG node) when the ‘attribute’ is queried. I believe using properties is key to harnessing the power of classes in Maya.

class GameThing(object):
	def __init__(self, node):
		self.node = node
	def controllers(self):
		return cmds.listConnections(self.node + ".controllers")

So now we can query the ‘controllers’ attribute/property, and it returns our controllers:

test = GameThing(loc)
print test.controllers
##>>[u'nurbsCircle2', u'nurbsCircle1']

Next up, we add a setter, which runs code when you set a property ‘attribute’:

class GameThing(object):
	def __init__(self, node):
		self.node = node
	def controllers(self):
		return cmds.listConnections(self.node + ".controllers")
	def controllers(self, cons):
		#disconnect existing controller connections
		for con in cmds.listConnections(self.node + '.controllers'):
			cmds.disconnectAttr(self.node + '.controllers', con + '.rigging')
		for con in cons:
			if cmds.objExists(con):
				if not cmds.attributeQuery('rigging', n=con, ex=1):
					cmds.addAttr(con, longName='rigging', attributeType='message', s=1)
				cmds.connectAttr((self.node + '.controllers'), (con + '.rigging'), f=1)
				cmds.error(con + ' does not exist!')

So now when we set the ‘controllers’ attribute/property, it runs a method that blows away all current message connections and adds new ones connecting your cons:

test = GameThing(loc)
print test.controllers
##>>[u'nurbsCircle2', u'nurbsCircle1']
test.controllers = [cmds.nurbsSquare()[0]]
print test.controllers

To me, something like properties makes classes infinitely more useful in Maya. For a short time we tried to engineer a DG node at Crytek that when an attr changed, could eval a string with a similar name on the node. This is essentially what a property can do, and it’s pretty powerful. Take a moment to look through code of some of the real ‘heavy lifters’ in the field, like zooToolBox, and you’ll see @property all over the place.

I hope you found this as useful as I would have.

posted by Chris at 1:03 AM  

Monday, January 7, 2013

Abusing ‘Blind Data’ in Maya

‘Blind data’ is custom data that you can store on any object or its components (vertex, edge, polygon, etc). The documentation says ‘Blind data is information stored with polygons which is not used by Maya in any way..’ I believe it is used when importing meshes from other apps that have properties that do not map to Maya, so that when you take them back to those apps, those properties remain.

Anyway, the important point here is that blind data is metadata (int, float, double, boolean, string, binary) that you can attach to any component. It matters not what happens to said component, you can extract a polygon from a mesh, it’s index will have changed, it’s object will have changed, but its blind data will remain with it. The only drawback can be that it can be painfully slow to write this data, but we will get to that later.

Simple Example

First let’s create a blind data template, this is required to store the data later. We use the command ‘blindDataType’ to create a template for a string type called ‘skinningInfo’ or ‘skin’ for short, giving it an ID 12344. Then we query the ID and it returns the blind data attribs we have created.

cmds.blindDataType(id=12344, dt='string', ldn='skinningInfo', sdn='skin')
print cmds.blindDataType(id=12344, tn=1, q=1)
>>['skinningInfo', 'skin', 'string']

So now we have our template, let’s try using it, this is more focused on getting the idea across than speed:

#query vertex # of mesh
v = cmds.polyEvaluate(node, v=1)
#loop through vertices
for vtx in range(0, v):
    #get influences
    infs = cmds.skinCluster(sc, inf=1, q=1)
    #get weights
    objVtx = node + ".vtx[" + str(vtx) + "]"
    vals = cmds.skinPercent(sc, objVtx, q=1, v=1)
    #build dict of influence:weight
    for i in range(0, len(infs)):
        weightDict[infs[i]] = vals[i]
    #write value to blind data
 cmds.polyBlindData(objVtx, id=12344, at='vertex', ldn='skinningInfo', sd=str(weightDict))

So here you have saved a dictionary per vertex that has key/value pairs of influence/weight. You can query like so:

#I have a vertex selected in component mode
print cmds.polyQueryBlindData(, id=12344, showComp=1)
['polySurface2.vtx[64].skin', "{u'joint2': 0.49755714634259796, 'joint3': 0.49755714634259784, 'joint1': 0.0048857073148042395}"]

Now On To Something More Useful

So let’s create a function to store skinning data per-vertex, as you may have seen with the above, that was painfully slow. If you have written any skinning tools, you know that the solution to this (other than learning C++) is to apply your change to all vertices at once. Below we build two lists, one of vertices and one of weights, then we

def storeBlindSkinning(mesh, sc):
	mesh is a skinned mesh, and sc is the skincluster affecting the mesh
	vtxList = []
	v = cmds.polyEvaluate(mesh, v=1)
	infs = cmds.skinCluster(sc, inf=1, q=1)
	vtxWeights = []
	for vtx in range(0, v):
	    objVtx = mesh + ".vtx[" + str(vtx) + "]"
	    vals = cmds.skinPercent(sc, objVtx, q=1, v=1)
	    for i in range(0, len(infs)):
        	weightDict[infs[i]] = vals[i]
        cmds.polyBlindData(vtxList, id=12344, at='vertex', ldn='skinningInfo', sd=vtxWeights)

Setting all the data at once is 1/3 faster, however, setting this data takes quite some time, and you may want to take a hit for a progress bar. (break it up into groups) On ~60,000 vertices this took 10min (15min doing it inside the loop). I don’t mind that hit if it means that I can now detach/alter/slice my mesh without losing skinning data. You can even extract faces and the new vertices created will get the same blind data as their original. (one becomes two)

As always, the C++ API is much faster, my colleague, Bogdan speed tested the above function and 50,000 vertices took only a few milliseconds, compared to 10 minutes in pythonland.

Remember, there are other ways to store skinning data, using UVs, position, vertex color channels, etc. I just wanted to introduce people to blind data in Maya and show a potential use.

posted by admin at 4:04 AM  

Monday, July 16, 2012

CINEBOX SIGGRAPH Talk and Studio Workshops


I am giving a talk at SIGGRAPH 2012 entitled ‘Film/Game Convergence: What’s Taking So Long?‘ where I discuss the inherent differences between games and film and go over a few case studies of projects that attempted to use a game engine for film previs. I also talk a bit about the development of our CINEBOX application, the decisions we had to make, and how we dealt with many of the issues previous attempts have run into.


I will be giving two more Studio Workshops this year, the first is a followup to last year’s Introduction to Python, entitled ‘Python Scripting in Maya‘. The other workshop is ‘Building a Game Level‘, which is the same basic workshop I gave last year where I show people how to make a playable game level in CryEngine in an hour. Studio Workshops are hands-on sessions where each attendee has a computer and follows along with the instructor. It’s a great chance for people of all ages to learn new things.

posted by admin at 8:06 PM  

Saturday, April 21, 2012

Maya: Walking the Line

I am still finding my feet in Maya, on my project, some files have grown to 800mb in size. Things get corrupt, hand editing MAs is common; I am really learning some of the internals.

In the past week I have had to do a lot of timeline walking to switch coord spaces and get baked animations into and out of hierarchies. In 3dsMax you can do a loop and evaluate a node ‘at time i’, and there is no redraw or anything. I didn’t know how to do this in Maya.

I previously did this with looping cmds.currentTime(i) and ‘walking the timeline’, however, you can set the time node directly like so: cmds.setAttr(“time1.outTime”, int(i))

Unparenting a child with keyed compensation (1200 frames)
10.0299999714 sec – currentTime
2.02 sec – setAttr

There are some caveats, whereas in a currentTime loop you can just cmds.setKeyframe(node), I now have to cmds.setKeyframe(node, time=i). But when grabbing a matrix, I don’t need to pass time and it works, I don’t think you can anyway.. I guess it gets time from the time node.

Here’s a sample loop that makes a locator and copies a nodes animation to world space:

#function feeds in start, end, node
	if not start: start = cmds.playbackOptions(minTime=1, q=1)
	if not end: end = cmds.playbackOptions(maxTime=1, q=1)
	loc = cmds.spaceLocator(name='parentAlignHelper')
	for i in range(start, (end+1)):
		cmds.setAttr("time1.outTime", int(i))
		matrix = cmds.xform(node, q=1, ws=1, m=1)
		cmds.xform(loc, ws=1, m=matrix)
		cmds.setKeyframe(loc, time=i)
posted by admin at 11:44 AM  

Tuesday, October 25, 2011

Quick Note About Range(), Modulus, and Step

Maybe it’s me, but I often find myself parsing weird ascii text files from others. Sometimes the authors knew what the data was and there’s no real markup. Take this joint list for example:

143 # bones
root ground
0 0 0
root hips
0 0.9512207 6E-08
spine 1
4E-08 0.9522207 1.4E-07
spine 2
3E-07 1.0324 8.3E-07
spine 3
5.6E-07 1.11357 1.53E-06
spine 4
8.2E-07 1.194749 2.22E-06
head neck lower

So the first line is the number of joints then it begins in three line intervals stating from the root outwards: joint name, parent integer, position. I used to make a pretty obtuse loop using a modulus operator. Basically, modulus is the remainder left over after division. So X%Y gives you the remainder of X divided by Y; here’s an example:

for i in range(0,20+1):
	if i%2 == 0: print i
#>> 0
#>> 2
#>> 4
#>> 6
#>> 8
#>> 10

The smart guys out there see where this is goin.. so I never knew range had a ‘step’ argument. (Or I believe I did, I think I actually had this epiphany maybe two years ago, but my memory is that bad.) So parsing the above is as simple as this:

jnts = []
for i in range(1,numJnts*3+1,3):
	jnt = lines[i].strip()
	parent = int(lines[i+1].strip())
	posSplit = lines[i+2].strip().split(' ')
	pos = (float(posSplit[0])*jointScale, \
	float(posSplit[1])*jointScale, float(posSplit[2])*jointScale)
	jnts.append([jnt, parent, pos])

Thanks to phuuchai on #python (efnet) for nudging me to RTFM!

posted by admin at 1:42 AM  

Wednesday, October 12, 2011

SIGGRAPH 2011: Intro To Python Course

I gave a workshop/talk at SIGGRAPH geared toward introducing people to Python. There were ~25 people on PCs following along, and awkwardly enough, many more than that standing and watching. I prefaced my talk with the fact that I am self-taught and by no means an expert. That said, I have created many python tools people use every day at industry-leading companies.

Starting from zero, in the next hour I aimed to not only introduce them to Python, but get them doing cool, usable things like:

  • Iterating through batches/lists
  • Reading / writing data to excel files
  • Wrangling data from one format to another in order to create a ‘tag cloud’

Many people have asked for the notes, and I only had rough notes. I love Python, and I work with this stuff every day, so I have had to really go back and flesh out some of what I talked about. This tutorial has a lot less of the general chit-chat and information. I apologize for that.

Installation / Environment Check

Let’s check to see that you have the tools properly installed. If you open the command prompt and type ‘python’ you should see this:

So Python is correctly installed, for the following you can either follow along in the cmd window (more difficult) or in IDLE, the IDE that python ships with (easier). This can be found by typing IDLE into the start menu:


Variables are pieces of information you store in memory, I will talk a bit about different types of variables.


Strings are pieces of text. I assume you know that, so let’s just go over some quick things:

string = 'this is a string'
print string
#>>this is a string
num = '3.1415'
print num

One thing to keep in mind, the above is a string, not a number. You can see this by:

print num + 2
#>>Traceback (most recent call last):
#>>  File "", line 5, in
#>>    print num + 2
#>>TypeError: cannot concatenate 'str' and 'int' objects

Python is telling you that you cannot add a number to a string of text. It does not know that ‘3.1415’ is a number. So let’s convert it to a number, this is called ‘casting’, we will ‘cast’ the string into a float and back:

print float(num) + 2
print str(float(num) + 2) + ' addme'
#>>5.1415 addme


Lists are the simplest ways to store pieces of data. Let’s make one by breaking up a string:

txt = 'jan tony senta michael brendon phillip jonathon mark'
names = txt.split(' ')
print names
#>>['jan', 'tony', 'senta', 'michael', 'brendon', 'phillip', 'jonathon', 'mark']
for item in names: print item

Split breaks up a string into pieces. You tell it what to break on, above, I told it to break on spaces txt.split(‘ ‘). So all the people are stored in a List, which is like an Array or Collection in some other languages.
You can call up the item by it’s number starting with zero:

print names[0], names[5]
#>>jan phillip

TIP: [-1] index will return the last item in an array, here’s a quick way to get a file from a path:

path = 'D:\\data\\dx11_PC_(110)_05_09\\Tools\\CryMaxInstaller.exe'
print path.split('\\')[-1]


These store keys, and the keys reference different values. Let’s make one:

dict = {'sascha':'tech artist', 'harry': 142.1, 'sean':False}
print dict['sean']

So this is good, but these are just the keys, we need to know the values. Here’s another way to do this, using .keys()

dict = {'sascha':'tech artist', 'harry': 142.1, 'sean':False}
for key in dict.keys(): print key, 'is', dict[key]
#>>sean is False
#>>sascha is tech artist
#>>harry is 142.1

So, dictionaries are a good way to store simple relationships of key and value pairs. In case you hadn’t notices, I used some ‘floats’ and ‘ints’ above. A float is a number with a decimal, like 3.1415, and an ‘int’ is a whole number like 10.

Creating Methods (Functions)

A method or function is like a little tool that you make. These building blocks work together to make your program.

Let’s say that you have to do something many times, you want to re-use this code and not copy/paste it all over. Let’s use the example above of names, let’s make a function that takes a big string of names and returns an ordered list:

def myFunc(input):
	people = input.split(' ')
	people = sorted(people)
	return people
txt = 'jan tony senta michael brendon phillip jonathon mark'
orderedList = myFunc(txt)
print orderedList
#>>['brendon', 'jan', 'jonathon', 'mark', 'michael', 'phillip', 'senta', 'tony']

Basic Example: Create A Tag Cloud From an Excel Document

So we have an excel sheet, and we want to turn it into a hip ‘tag cloud’ to get people’s attention.
If we go to you will see that in order to create a tag cloud, we need to feed it the sentences multiple times, and we need to put a tilde in between the words of the sentence. We can automate this with Python!

First, download the excel sheet from me here: [info.csv] The CSV filetype is a great way to read/write docs easily that you can give to others, they load in excel easily.

file = 'C:\\Users\\chris\\Desktop\\intro_to_python\\info.csv'
f = open(file, 'r')
lines = f.readlines()
print lines
#>> ['always late to work,13\n', 'does not respect others,1\n', 'does not check work properly,5\n', 'does not plan properly,4\n', 'ignores standards/conventions,3\n']

‘\n’ is a line break character, it means ‘new line’, we want to get rid of that, we also want to just store the items, and how many times they were listed.

file = 'C:\\Users\\chris\\Desktop\\intro_to_python\\info.csv'
f = open(file, 'r')
lines = f.readlines()
dict = {}
for line in lines:
	split = line.strip().replace(' ','~').split(',')
	dict[split[0]] = int(split[1])
print dict
#>>{'ignores~standards/conventions': 3, 'does~not~respect~others': 1, 'does~not~plan~properly': 4, 'does~not~check~work~properly': 5, 'always~late~to~work': 13}

Now we have the data in memory in an easily readable way, let’s write it out to disk.

output = ''
for key in dict.keys():
	for i in range(0,dict[key]): output += (key + '\n')
f = open('C:\\Users\\chris\\Desktop\\intro_to_python\\test.txt', 'w')

There we go. In one hour you have learned to:

  • Read and write excel files
  • Iterate over data
  • Convert data sets into new formats
  • Write, read and alter ascii files

If you have any questions, or I left out any parts of the presentation you liked, reply here and I will get back to you.

posted by admin at 5:12 AM  

Tuesday, October 4, 2011

Question: Rigging with MetaData?

As many of you know, I feel the whole ‘autorigging’ schtick is a bit overrated. Though Bungie gave a great talk at GDC09 (Modular Procedural Rigging), Dice was to give one this year at SIGGRAPH (Modular Rigging in Battlefield 3), but never showed up for the talk.

At Crytek we are switching our animation dept from 3dsMax to Maya. This forces us to build a pipeline there from scratch; in 3dsMax we had 7 years of script development focused on animation and rigging tools. So I am looking at quite a bit o Maya work. The past two weeks focusing on a ‘rigging system’ that I guess could be thought of as ‘procedural’ but is not really an ‘autorigger’. My past experience was always regenerating rigs with mel cmds.

Things I would like to solve:

  • Use one set of animator tools for many rigs – common interfaces, rig block encapsulation (oh god i said ‘block’)
  • Abstract things away, thinking of rigging ‘units’ and character ‘parts’ instead of individual rig elements, break reliance on naming, version out different parts
  • Be fluid enough to regenerate the ‘rigging’ at any time

First Weekend: Skeleton ‘Tagging’

I created a wrapper around the common rigging tools that I used, this way, when I rigged, it would automagically markup the skeleton/elements as I went. This looked like so:

The foundation of this was marking up the skeleton or cons with message nodes that pointed to things or held metadata.  This was cool, and I still like how simple it was, however, it didn’t really create the layer of abstraction I was after. There wasn’t the idea of a limb that I could tell to switch from FK to IK.

Second Weekend: Custom Nodes

That Bungie talk got a lot of us all excited, Roman went and created a really cool custom node plugin that does way more than we spec’d it out to do. I rewrote the rigging tools to create ‘rigPart’ nodes, which could be like an IK chain, set of twist joints, expression, or constraint. These together could form a ‘charPart’ like an arm or leg. All these nodes sat under a main ‘character’ node. I realize that many companies abstract their characters into ‘blocks’ or ‘parts’, but I had never seen a system that had another layer underneath that. Roman also whipped up a way that when an attr on a customNode changes, you could evaluate a script. So whether it’s a human arm or alien tentacle arm, the ‘charPart’ node can have one FK/IK enum. I am still not sure if this is a better idea, because of the sheer legwork involved..

Third Weekend: A Mix of Both?

So a class like ‘charParts.gruntLeg()’ not only knew how to build the leg rigParts, but also only the leg ‘rigging’ if needed. This works pretty well, but the above was pretty hard to read. I took some of my favorite things about the tree-view-based system and I created a ‘character’ outliner of sorts. This made it much easier to visualize the rigParts that made up individual ‘systems’ of the character, like leg, spine, arm, etc. I did it as a test, but in a way that I easily swap it out with the treeWidget in the rigging tools dialog.

So how do you guys solve some of these issues?

posted by Chris at 4:00 AM  

Tuesday, July 19, 2011


I am volunteering again in the Studio; giving three small talks at SIGGRAPH, drop me a line if you will be in Vancouver.

Rigging Characters for CryENGINE

How to rig, skin, and export a character for CryENGINE 3. Topics include physics setup, building characters from many skinned meshes, and creating Character Definitions and Character Parameter files. These rigging basics are applicable to most run-time game engines.

Introduction to Python Scripting

In this introduction to Python, a powerful scripting language used by many 3D applications, attendees learn the basics and explore small example scenarios gleaned from actual game and film productions. The sessions are taught in a way that should empower attendees to immediately begin creating time-saving python scripts and applications.

World Creation in CryENGINE

Have you ever wanted to make a videogame? This session shows how to build a small level in the freely available CryENGINE 3 SDK. Topics include: world building and tools (FlowGraph, CryENGINE’s visual scripting language, and Trackview, the camera sequencing and directing tools). In less than an hour, attendees create their own playable video games.

posted by admin at 9:32 AM  

Monday, October 4, 2010

Writing Custom Perforce Plugins in Python

I recently wrote a custom tool to diff CryEngine layer files in P4, and was surprised how simple it was. What follows is a quick tutorial on adding custom python tools to Perforce.

Start by heading over to Tools>Manage Custom Tools… Then click ‘New’:

You can pass a lot of information to an external tool, here is a detailed rundown. As you see above, we pass the client spec (local) file name (%f) to a python script, let’s create a new script called ‘’:

import sys
from PyQt4 import QtGui    
class custom_tool(QtGui.QMessageBox):
	def __init__(self, parent=None):
if __name__ == "__main__":
	app = QtGui.QApplication(sys.argv)
	theTool = custom_tool()

What this does is simply spits out the sys.argv in a way you can see it. So now you can feed any file you right click in Perforce into a python script:

If you would like to actually do something with a file or revision on the server and are passing the %F flag to get the depot file path, you then need to use p4 print to redirect the file contents (non-binary) to a local file:

p4.run_print('-q', '-o', depotFile, localFile)
posted by admin at 1:09 AM  

Thursday, August 26, 2010

Perforce Triggers in Python (Pt 1)

Perforce is a wily beast. A lot of companies use it, but I feel few outside of the IT department really have to deal with it much. As I work myself deeper and deeper into the damp hole that is asset validation, I have really been writing a lot of python to deal with certain issues; but always scripts that work from the outside.

Perforce has a system that allows you to write scripts that are run, server side, when any number of events are triggered. You can use many scripting languages, but I will only touch on Python.

Test Environment

To follow along here, you should set up a test environment. Perforce is freely downloadable, and free to use with 2 users. Of course you are going to need python, and p4python. So get your server running and add two users, a user and an administrator.

Your First Trigger

Let’s create the simplest python script. It will be a submit trigger that says ‘Hello World’ then passes or fails. If it passes, the item will be checked in to perforce, if it fails, it will not. exiting while returning a ‘1’ is considered a fail, ‘0’ a pass.

print 'Hello World!'
print 'No checkin for you!'

Ok, so save this file as Now go to a command line and enter ‘p4 triggers’ this will open a text document, edit that document to point to your trigger, like so (but point to the location of your script on disk):

	hello_trigger change-submit //depot/... "python X:/projects/2010/p4/"

Close/save the trigger TMP file, you should see ‘Triggers saved.’ echo’d at the prompt. Now, when we try to submit a file to the depot, we will get this:

So: awesome, you just DENIED your first check-in!

Connecting to Perforce from Inside a Trigger

So we are now denying check-ins, but let’s try to do some other things, let’s connect to perforce from inside a trigger.

from P4 import P4, P4Exception
p4 = P4()
	#use whatever your admin l/p was
	#this isn't the safest, but it works at this beginner level
	p4.user = "admin"
	p4.password = "admin"
	p4.port = "1666"
	info ="info")
	print info
#this will return any errors
except P4Exception:
	for e in p4.errors: print e

So now when you try to submit a file to depot you will get this:

Passing Info to the Trigger

Now we are running triggers, accepting or denying checkins, but we really don’t know much about them. Let’s try to get enough info to where we could make a decision about whether or not we want the file to pass validation. Let’s make another python trigger,, and let’s query something from the perforce server in the submit trigger. To do this we need to edit our trigger file like so:

	test change-submit //depot/... "python X:/projects/2010/p4/ %user% %changelist%"

This will pass the user and changelist number into the python script as an arg, the same way dragging/dropping passed args to python in my previous example. So let’s set that up, save the script from before as ‘’ as shown above, and add the following:

import sys
from P4 import P4, P4Exception
p4 = P4()
describe = []
	p4.user = "admin"
	p4.password = "admin"
	p4.port = "1666"
except P4Exception:
	for e in p4.errors: print e
print str(sys.argv)
describe ='describe',sys.argv[2])
print str(describe)

So, as you can see, it has returned the user and changelist number:

However, for this changelist to be useful, we query p4, asking the server to describe the changelist. This returns a lot of information about the changelist.

Where to Go From here

The few simple things shown here really give you the tools to do many more things. Here are some examples of triggers that can be  created with the know-how above:

  • Deny check-ins of a certain filetype (like deny compiled source files/assets)
  • Deny check-ins whose hash digest matches an existing file on the server
  • Deny/allow a certain type of file check-in from a user in a certain group
  • Email a lead any time a file in a certain folder is updated

Did you find this helpful? What creative triggers have you written?

posted by admin at 12:33 AM  

Monday, June 28, 2010

Python: Simple Decorator Example

In Python, a Decorator is a type of macro that allows you to inject or modify code in functions or classes. I was turned onto this by my friend Matt Chapman at ILM, but never fully grasped the importance.

class myDecorator(object):
	def __init__(self, f):
		self.f = f
	def __call__(self):
		print "Entering", self.f.__name__
		print "Exited", self.f.__name__
def aFunction():
	print "aFunction running"

When you run the code above you will see the following:

>>Entering aFunction
>>aFunction running
>>Exited aFunction

So when we call a decorated function, we get a completely different behavior. You can wrap any existing functions, here is an example of wrapping functions for error reporting:

class catchAll:
	def __init__(self, function):
		self.function = function
	def __call__(self, *args):
			return self.function(*args)
		except Exception, e:
			print "Error: %s" % (e)
def unsafe(x):
  return 1 / x
print "unsafe(1): ", unsafe(1)
print "unsafe(0): ", unsafe(0)

So when we run this and divide by zero we get:

unsafe(1):  1
unsafe(0):  Error: integer division or modulo by zero

Using decorators you can make sweeping changes to existing code with minimal effort, like the error reporting function above, you could go back and just sprinkle these in older code.

posted by admin at 9:06 AM  

Saturday, June 26, 2010

Python: Special Class Methods

I have really been trying to learn some Python fundamentals lately, reading some books and taking an online class. So: wow. I can’t believe that I have written so many tools, some used by really competent people at large companies, without really understanding polymorphism and other basic Python concepts.

Here’s an example of my sequence method from before, but making it a class using special class methods:
class imSequence:
	def __init__(self, file):
		dir = os.path.dirname(file)
		file = os.path.basename(file)
		segNum = re.findall(r'\d+', file)[-1]
		self.numPad = len(segNum)
		self.baseName = file.split(segNum)[0]
		self.fileType = file.split('.')[-1]
		globString = self.baseName
		for i in range(0,self.numPad): globString += '?'
		self.images = glob.glob(dir+'\\'+globString+file.split(segNum)[1])
	def __len__(self):
		return len(self.images)
	def __iter__(self):
		return iter(self.images)

Here’s an example of use:

seq = imSequence('seq\\test_00087.tga')
print len(seq)
print 'BaseName: %s  FileType: %s  Padding: %s' % (seq.baseName, seq.fileType, seq.numPad)
>>BaseName: test_  FileType: tga  Padding: 5
for image in seq: print image

[More info and examples: Dive Into Python: Special Class Methods]

posted by admin at 10:16 PM  

Monday, April 19, 2010

Dealing with File Sequences in Python

I have been parsing through the files of other people a lot lately, and finally took the time to make a little function to give me general information about a sequence of files. It uses regex to yank the numeric parts out of a filename, figure out the padding, and glob to tell you how many files in the sequence. Here’s the code and an example usage:

#returns [base name, padding, filetype, number of files, first file, last file]
def getSeqInfo(file):
	dir = os.path.dirname(file)
	file = os.path.basename(file)
	segNum = re.findall(r'\d+', file)[-1]
	numPad = len(segNum)
	baseName = file.split(segNum)[0]
	fileType = file.split('.')[-1]
	globString = baseName
	for i in range(0,numPad): globString += '?'
	theGlob = glob.glob(dir+'\\'+globString+file.split(segNum)[1])
	numFrames = len(theGlob)
	firstFrame = theGlob[0]
	lastFrame = theGlob[-1]
	return [baseName, numPad, fileType, numFrames, firstFrame, lastFrame]

Here is an example of usage:

print getSeqInfo('E:\\data\\data\\Games\\Project\\CaptureOutput\\Frame000547.jpg')
>>['Frame', 6, 'jpg', 994, 'E:\\data\\data\\Games\\Project\\CaptureOutput\\Frame000000.jpg', 'E:\\data\\data\\Games\\Project\\CaptureOutput\\Frame000993.jpg']

I know this is pretty simple, but I looked around a bit online and didn’t see anything readily available showing how to deal with different numbered file sets. I have needed something like this for a while that will work with anything from OBJs sent from external contractors, to images from After Effects…

posted by admin at 6:49 PM  

Monday, April 12, 2010

Drop Files on a Python Script

So I have always been wondering how you can create almost like a ‘droplet’ to steal the photoshop lingo, from a python script. A while ago I came across some sites showing how to edit shellex in regedit to allow for files to be dropped on any python script and fed to it as args (Windows).

It’s really simple, you grab this reg file [py_drag_n_drop.reg] and install it.

Now when you drop files onto a python script, their filenames will be passed as args, here’s a simple script to test.

import sys
f = open('c:\\tmp.txt', 'w')
for arg in sys.argv:
    f.write(arg + '\n')

When you save this, and drop files onto its icon, it will create tmp.txt, which will look like this:

X:\photos\2010.04 - easter weekend\fuji\DSCF9048.MPO
X:\photos\2010.04 - easter weekend\fuji\DSCF9049.MPO
X:\photos\2010.04 - easter weekend\fuji\DSCF9050.MPO
X:\photos\2010.04 - easter weekend\fuji\DSCF9051.MPO
X:\photos\2010.04 - easter weekend\fuji\DSCF9052.MPO

The script itself is the first arg, then all the files. This way you can easily create scripts that accept drops to do things like convert files, upload files, etc..

posted by admin at 12:33 AM  

Sunday, April 11, 2010

MPO to JPS and PNS

I got some good feedback from the last post and updated the script to export JPEG Stereo (JPS) and PNG Stereo (PNS, really.) This way you can convert your images into a single lossless image that you can pop into photoshop and adjust hsv/levels, etc.

import mpo
#>>Saving image: DSCF9463.PNS
#>>Save complete.

This is a super simple python script, no error padding. Also, keep in mind that coming from most modern camera rigs, you are saving like a 20-40 megapixel PNG compressed file here, wait until it says it is done saving, it may take a few seconds.

posted by admin at 10:31 PM  
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