Oct 122012
 

PyQt4 UI Development for Maya

Just released my 3rd python-based online training video through cmiVFX.com

Introduction

This tutorial is about learning PyQt4 python bindings for the Qt Framework, and how to introduce new UI elements to Maya as a platform.
We discuss what comprises a “Framework” and a “GUI Framework”, and how Qt and PyQt4 work together.

 

Getting Started With PyQt4

There are multiple ways of getting a working installation of PyQt4, both for the general system and for Maya. We look into these approaches to get your system up and running to begin working with PyQt4!
We also talk about what is included, such as command line tools and applications, tips on how to test and learn the code, and how to structure a project.

 

PyQt4 Fundamentals

Lets get crackin’ and learn the basics!
• What is a QObject? What is a QWidget? Common PyQt4 classes are explained in detail
• Working with the Qt Designer application, to build a UI visually
• Layouts: Making widgets resize elegantly and stay organized in your design
• Coordinate space: How do widgets transform in your 2D screen space?
• QApplication and the Qt Event Loop: The engine that runs your UI
• Events, Signals, and Slots: How components communicate changes and how the application can respond to changes to make it dynamic

 

General Examples

With an understanding of the framework components, we can begin working with fully functional stand-alone examples.
• Common PyQt4 app template
• Subclassing Widgets: Creating custom functionality to the existing classes provided by PyQt4
• Dialogs: Raising dialog windows above existing windows, Modal vs Non-modal, and creating forms. We look at different ways to validate the data provided by the user, to these dialog forms.

 

PyQt4 And Maya Introduction

Finally, some Maya action! Maya has a slightly different approach to using PyQt4…
• How does the QApplication and event loop work?
• Common Maya PyQt4 app template
• Looking at the Maya API’s MQtUtil class
• The sip module: Helping us translate between Maya’s Qt and our own PyQt4 code

 

Replicating Maya’s UI Components

What better way to see examples of creating UI for Maya than to replicate some existing functionality? This gives us the opportunity expand with custom functionality
In this chapter we will take two different UI components in Maya, and do a basic custom version of our own, and show to how link them up to Maya’s own callbacks.
Some Features Of This Chapter Include
• The QTableWidget
• Model / View separation with QTreeView
• Docking windows into the Maya interface
• Mixing together PyQt4, the Maya API, Maya commands, and callbacks
• Sorting model data

 

Customizations

A button can be a button, and a slider might look alright in its stock form, but sometimes we want to customize the look of our widgets. This chapter introduces multiple ways of achieving custom looks to our components
• Stylin’ Stylesheets: Use CSS-like syntax for applying style sheets to widgets
• Painting By … Paint events: For even more control, we can tell a widget exactly how to draw itself on the screen. We will look at two different examples of how to use custom painting.

Previous cmiVFX tutorials:

Jul 252012
 
python-logo

In a recent python project where I was sending multiple messages per second of data over a basic socket, I had initially just grabbed the cPickle module to get the prototype proof-of-concept functioning properly. cPickle is awesome for easily serializing more complex python objects like custom classes, even though in my case I am only sending basic types.

My messages were dicts with some nested dicts, lists, floats, and string values. Roughly 500-1000 bytes. cPickle was doing just fine, but there came a point where I wanted to investigate the areas that could be tightened up. The first thing I realized was that I had forgotten to encode cPickle in the binary format (the default is ascii). That saved me quite a bit of time. But then I casually searched online to see if any json options might be better since my data is pretty primitive anyways.

I found UltraJSON, which is a pure C json parsing library for python, and ran some tests. There are benchmarks on the project page for ujson, as well as other articles on the internet, but I just wanted to post up my own results using a mixed type data container. ujson came out extremely fast: faster than binary cPickle and msgpack, in the encoding test. Although in the decoding test, msgpack appeared to be fastest, followed by binary cPickle, and then ujson coming in 3rd

This test included the following:

Here is my Python 2.7.2 test script using timeit for each encode and decode step.
Jun 212012
 
kinect-xl

A recent project of mine involves research and development with an XBOX 360 Kinect Sensor. Being a python guy, I started searching for python bindings to some OSX-supported framework. When you just get started looking into this area it can be a little confusing. There are a number of layers to the software stack to enable one to accomplish anything meaningful. This is just a short and general blog post outlining the basics of what I have discovered thus far, to help anyone else that might also be getting started.

At the lowest level, you need a driver. Something that can talk to the USB device that is the Kinect sensor. When you purchase the XBOX Kinect for Windows version of the sensor, and you are going to be developing on windows, much of this whole stack is provided to you by way of the Kinect SDK. But for the open source folks with the standard XBOX 360 sensor, you need to piece together your own solution.

Two drivers that I have discovered thus far:

I had started OpenKinect (libfreenect) because it comes with a python wrapper included. There were a few dependencies (I will talk about specific build steps in just a moment), but once I got this installed I was able to fire up the included  glview app and see both depth and rgb data streaming in from my sensor. The role of these drivers is to provide simply the basic streams. That is, the depth, rgb, audio, and a few other sensor data streams. If your goal is to start tracking players, seeing skeletons, and registering gestures, the drivers are not enough. You would be required to make your own solution from this raw data at this phase in the game.

You would now want to look into middleware that can take the raw data and provide to you an API with higher level information. This would include finding users in the scene for you, tracking their body features, and giving you various events to watch for as the data streams.

Being that my goal was to have python bindings, I found my options to be much more limited than if I were going to be developing in C++. Wrappers have to exist for the framework you want. This is where my research really started ramping up. I spent a few days dealing wtih compiling issues, as well as having an actual bad power adapter that had to be exchanged. But all said and done, here is what I have settled on thus far…

  1. Driver: PrimeSense Sensor
  2. OpenNI Framework
  3. NITE middleware for OpenNI
  4. PyOpenNI python bindings

Install Details

Install homebrew (package manager)

http://mxcl.github.com/homebrew/

Install build tools

Install python2.7

Suggestion: virtualenv Environment

This is not a requirement. But I recommend using virtualenv to set up an environment that specifically uses python2.7 so that you don’t have to fight with mixed dependencies and versions.

Create a virtualenv called “kinect”

Install libusb (patched version)

There is a special patched version of the libusb library, in the form of a homebrew formula.

Now copy platform/osx/homebrew/libusb-freenect.rb -> /usr/local/Library/Formula/

Install SensorKinect drivers

Then uncompress Bin/SensorKinect093-Bin-MacOSX-v*tar.bz2

Install OpenNI framework
  1. Go here: http://www.openni.org/Downloads/OpenNIModules.aspx
  2. Download Unstable Binary for MacOSX
  3. sudo ./install.sh
Install NITE middleware (for OpenNI)
  1. Go here: http://www.openni.org/Downloads/OpenNIModules.aspx
  2. Download Unstable MIDDLEWARE of NITE for OSX
  3. sudo ./install.sh
Install PyOpenNI

Be aware that on OSX, PyOpenNI requires a framework build of python 2.7+ and that you must build it for x86_64 specifically. Also, I was having major problems with cmake properly finding the python includes location. I had to suggest a fix, so please see here for the necessary corrections. I have referenced a patched fork of the repository below.

copy the lib/openni.so module to the python2.7 site-packages

Examples

Once you have everything installed, you can try out the examples that are included both in the NITE source location that you downloaded and also in the PyOpenNI source location:

  1. NITE/Samples
  2. PyOpenNI/examples
I also tried out ofxKinect (github.com/ofTheo/ofxKinect) on the side, which is an addon for  OpenFrameworks. This is kind of a separate path than the OpenNI stack. I would say its more like an advanced offering of libfreenect. Using the included example, I recorded a 3D point cloud that is built on the fly from the RGB and depth data:

 

Apr 142012
 

Permalink - writemycode.net

In the spirit of a very similar blog post, I decided to expand upon a specific area of that article…

Consider a question like this:

I want to do this. Create 10000 files, (filename can be just combination of time and random number). File size should be 4k. And I want to time this. say how many seconds it will take.

How can I do this on bash?

Thank you.

Obviously this person needs some assistance, and the question is very short and easy to understand. But the problem with this type of question is that there are really only two ways someone can approach the answer. Your options for an answer are either to just give the person the complete code snippet as they have requested, or fall back on a lengthy personalized tutorial.

Short questions that primarily request a complete code example as an answer are counter-productive to code communities.

Answer Option 1

As the topic of this article suggests, option 1 is “Write my code for me”. It might seem easy as a one-off situation to simply donate a working code snippet and get the person asking this question moving on their merry way, but really this is not helping them in the long run. They haven’t learned anything beyond the process of hitting a roadblock, then immediately going online to ask for a solution. Had this person included some references to what they have researched, and most importantly a code snippet representing what they have attempted, viewers of this question would have a basis for comment and potentially an answer pointing out where the person has gone wrong.

Answer Option 2

And in the other direction: providing a lengthy tutorial. We all want to help and teach, but this is just one of numerous questions floating out in the ether that requires a response. Can we really spare that much time for every single question like this to re-teach material that is most likely already documented in generalized contexts all across the internet? That would create quite a lot of redundant information simply because each person combines new components into a new question needing a new lesson. Really, every part of this question can be Googled quite easily. Why ask a community to do a new custom writeup for you?

Now, assuming we actually wanted to write a tutorial for this person asking the question. The problem at this point is where do we begin? The information provided doesn’t suggest that this person has a grasp on any part of the problem. So the tutorial answer might need to include:

  1. Bash and for-loops
  2. How to get the current time
  3. How to generate random numbers
  4. Creating files
  5. Populating new files to a specific size
  6. How to write a complete bash script, and time its execution.

Had they told us what they know how to do so far, and what aspect has them stuck, we could simply focus on one area and provide a good bit of knowledge to get them moving again. But right now this is just too much work to net a situation where they will learn something.

For those that are immediately inclined to provide the complete code snippet to solve the problem, where do we draw the line? What if the question being asked would need 10 lines of code? 20? 100? And if you are also interested in frequently helping people, would you be willing to provide 5 lines of complete code to 10 people a day, knowing that each person probably didn’t learn much? Furthermore, after having given this individual a quick answer, you have now rewarded their lazy behavior, and more than likely just encouraged them to repeat the bad habit again.

Through a conversation between my coworker and I, some interesting metaphors were raised that I simply can’t resist from sharing…

Vending-machine communities

Put a question in the slot and pop out a solution.  
Be it a traditional forum, an online discussion group, mailing list, or a trust and reputation based technical site like stackoverflow.com, these communities are driven by people, not machines. People have to take time to review content, and contribute their knowledge. We all work hard to acquire that knowledge, so lets all try and put some value on it in the form of the quality of our questions. A .25 cent answer is insulting. Treat your questions like they are costing you actual money that properly reflects the value of people’s knowledge. Code communities don’t work for you, and you don’t work for them. We are all here to help because we love it. Please don’t make us hate it, or feel like we are all just part of a big vending-machine.

Toilet paper answers

Answers that can be used only one particular time for one particular situation.
There is an insane amount of content on the internet. It’s hard enough sometimes to sift through the results of a vague Google search, let alone the content on our individual communities. When you ask a question that provides zero context, or proof of the extent of your current effort, then both the question and the answer are for the most part “throw aways”. If its going to be a persistent part of a community space, it should aim to benefit future support-seekers with similar situations. Referring to the example question above, someone going with Option 1 (“Write my code”) will end up providing an answer that will likely not help many people beyond this situation. Unless they too are looking for a way to do a for loop and create 10,000 4k dummy files and measure the execution time. The only way it would stand to benefit future visitors is if the answer did Option 2 and wrote a fully self-describing tutorial.

Conclusion

I can only speak for myself about what I might do. I consider myself to be the type that would go as far as to look at API docs for someone, and work out some pretty extensive examples on my local machine. I might even install libs that I don’t have or have never used before in an effort to provide assistance. But I need to be motivated to do so. It’s exciting for me to write out a page-length of information if I know it will help this person. But in a case like the above there is no show of effort and no context provided — just a person asking to have code written for them.

As I suggested already, we all want to help. Thats why we frequent these forums and sites. But we help these types of answer-seekers even more by withholding instant gratification.

And now… I direct you back to whathaveyoutried.com

 

Nov 202011
 

A question came up in the Maya-Python mailing list that I thought was a really good topic, and should be reposted.

Someone asked how you can create maya UI objects and embed them within your main PyQt application. Specifically he wanted to create a modelPanel and embed it so that he would have a camera view within his own PyQt window.

Here is my example of how to achieve this…

You need sip and the MQtUtil functions to convert between maya node paths and python Qbjects. Its the same idea as having to use those functions to get a reference to the maya MainWindow, in order to parent your dialog.

Nov 152011
 

Second video in the python for maya series, just released through cmiVFX!

Python For Maya – Volume 2

If you watched the first video, you now have a good grasp on Python. Sweet. Let’s plow through some more involved concepts like python juggernauts!

With a working knowledge of the python scripting language, and the Maya Python commands API, we can continue to learn new ways to solve more challenging problems, create complete scripts, and build user interfaces around our tools. We also introduce the Maya Python API; a lower-level interface into Maya.

This video focuses more on breaking down full scripts, as opposed to typing out syntax. Its jam packaged with information and moves fast to deliver you as much brain food as possible. The first segment of the video transitions from beginning to intermediate level, with the majority of the video being intermediate, and finishing out by touching on advanced concepts. The included project files are abundant, complete, and full of helpful documentation so that you can take your time and learn about each piece of the tools.

If you check it out, leave me feedback!
http://cmivfx.com/store/328-Python+For+Maya+Vol+02

First video can be found here

Nov 092011
 

This is a follow up post to my previous one on Installing PyQt4 for Maya 2011

Recently while putting together my next video tutorial for Python for Maya, I came to a section where I wanted to demo PyQt4 in Maya2012. But I was concerned that viewers would have to go through the complicated steps of building PyQt4. I noticed that other people have made available precompiled PyQt installers for windows (here) but I could not find any for OSX or linux. So I decided to put together a build.

I created a new project on github called MyQt4
https://github.com/justinfx/MyQt4

Its a Makefile for completely downloading and building PyQt4 for maya, and generating a .pkg installer. Hopefully someone can contribute improvements since I dont have a ton of experience writing makefiles, and also that someone might create a linux version.

Here is a link to the latest pkg build:

Snow Leopard: 

Lion:  

Mountain Lion:

Here are builds other people have made:

Oct 082011
 

Just released my first online video tutorial, through cmiVFX

Python Introduction Vol 01 – Maya

Amazing at Animation? Master of Modeling? Conquistador of Character Rigging?

But how is your Python?

This course brings the talented artist into the fold of the technical-side of Maya. Learn the basics of Python, and its place in your 3D workflow, with visual examples and real world problems. Get a kick-start on adding some automation into your life, and solving common problems in a fraction of the time. By the end of this video, you should have a deeper understanding of one of the languages Maya speaks under the hood, and how to start viewing your scenes in terms of glorious Python code!

Check it out: http://cmivfx.com/store/320-Python+Introduction+Vol+01+-+Maya

If you check out this course, please leave me some feedback! I would love to hear your thoughts.
Stay tuned for more installments to come!

Jul 282011
 

Preface

I’ve been programming in python for over 5 years now, and I love the language a lot. I would look for any opportunity to accomplish my coding tasks using python, as opposed to learning new languages. PyQt4 for user interfaces, Django for web design, etc… And when python just isn’t an option, I have done my share of php, javascript, objective-c and so on.
Recently I started thinking that I should probably expand my programming knowledge a bit to make myself more marketable. While python is pretty key in the world of Visual Effects pipelines… so is C++. Having previously focused on being a Compositor and not a programmer, I had always told myself that if I needed to learn C++, then I was going too far in that direction. But now that I have been working in pipeline development for over 2.5 years, it has become clear that I really should explore the world of compiled languages.

Grabbing some books on C+, I dove in. Yuk. Why is it so freaking boring? It really does suck trying to learn C++ after having been so spoiled with python for so long. Its like taking a Aborigine and trying to turn him into a snooty English gentleman. Hmm…Is that right? Well whatever. Its completely disorienting. So many things that I never had to think about, like type declarations, memory management, pointers… But I kept on reading and learning.

Then I came across a post on Google+, by someone that actually works at Google, mentioning a language being developed in-house. So I started reading about Go @ http://golang.org/

The Go Language

From the standpoint of a python programmer, Go feels like it sits right between C/C++ and python. You get the simpler syntax, but with the speed of a compiled language. Because Go has garbage collection, memory management isn’t a concern. I was never used to the code/compile/test/repeat pattern before, but it compiles so fast and is so easy to set up a project that it feels pretty natural. Go doesn’t require you to have header files and declare everything in advance, so banging out a simple program is quite fast and only slightly more overhead than writing a python script. Just have to add the step of compiling it. As far as the library, so far I have found everything pretty useful. And it seems that every time I search for a Go binding for something, I find one. I will go into more detail on that in a bit.

One thing that will make python programmers feel more at home is the type inference while creating a variable. While you can do something like this in Go:  

var myString string = “Foo”

you can also type the same thing like this:  

myString := “Foo”

:= operator lets you initialize a new variable and makes the compiler figure out what type it should be, based on the return type of the right hand side.

Pointers are still kind of strange for python programmers, but Go is a lot more flexible about using them. You don’t always have to explicitly dereference them like   (*myPointer).myFunction(). It just does it for you when you access member functions and attributes:  myPointer.myFunction().

Having no type inheritance is also a bit different as well. Instead of creating base abstract classes, and subclassing them, you only have structs… no classes. But you share functionality by using interfaces. An interface is just a definition of methods. If any object implements those methods, its consider that type of interface. This is something I have yet to really get into, since my current first project is more of a cmd program, rather than a pkg library. I’m sure I could be using interfaces already, but it hasn’t quite felt natural enough to incorporate as of yet.

A pretty crazy aspect of Go is its native support for concurrency using what they call “Goroutines”. The closest way I have been able to compare it to my experience in python is while using ZeroMQ for messaging. ZeroMQ promotes not only using its library for messaging, but also to replace issues with threads and locks. It has similar concepts in promoting concurrency. You divide your program up into its components and instead of sharing data structures between them, you communicate over channels (sockets in ZeroMQ). When you fire off a Goroutine, you aren’t waiting for it anymore. It can run and do its thing and you keep on going. You can then send data back and forth with channels, and even use them just for signaling, like saying “ok now exit”.

Actual Usage

I’ve been writing a message server so far in python, using the Tornado web server, along with some socket.io bindings called TornadIO, and also ZeroMQ for internal communication. So far its been working pretty well, but there are a lot of complex layers, with ZeroMQ sort of riding on top of Tornados ioloop. I decided to try and rewrite this server in Go. Turns out Go has a lot of built-in support for doing exactly what this python server was doing. The whole web-socket server functionality is part of the standard http library module. I quickly found Go bindings for socket.io and I was on my way.

It was quite fast to get the server to the point of doing global messages, but now I had to think about implementing the support for channel subscriptions. My first instinct was to go grab ZeroMQ and its bindings again, or to use Redis for the messaging, but then I was thinking “Shouldn’t I be able to do all this with Go’s concurrency?”. One thing that really helped me out was how fast everyone responds on the golang-nuts discussion group. It was quickly pointed out by more than one person that I should definitely be able to accomplish the internal message routing purely in Go. And they were right. I just set up a “dispatcher” function and run it in a loop as a goroutine, and then pass messages in and out of it. The dispatcher manages its data structure, and no other part of the code accesses it directly.

So far, this Go server is turning out great, and I’m excited by the fact that its compiled and faster. I don’t have to distribute my source code now :-)

Performance

* Disclaimer: These numbers are just comparisons between what I built in python vs Go. I think the point is to reflect what I naturally came up with on my first pass at using Go, vs applying years of python experience. I’m dead sure my Go code isn’t written as efficiently as someone with more experience, which I think makes it even more interesting of a comparison.

Go comes with built in testing and benchmarking functionality. What I built was a client test that connects to a running server and rapid fires messages. It times how long it takes for a 150 byte message to be sent out, flow through the server, and come back to that client as been delivered. The gotest utility that is used to run the test code will run the test, and if it ran too fast to calculate timings, it will repeat the test over and over with larger iterations. When I first got my Go server working to where a client would send a message and it would just get broadcasted right back out to everyone, I ran a benchmark. Here are the results of my tests…

TEST TIME PER MSG NET RESULT
Python (Tornado, …) 835314 ns/op -
Go (barebones messaging) 107091 ns/op 7.8x faster
Go (1-to-1 python port) 159823 ns/op 5.2x faster
Go (weekly.12-01-2011) 76230 ns/op 11x faster

 

The second Go test was after I finished implementing the same 1-to-1 feature set of the python version. I had thought the numbers would be dramatically impacted after adding the overhead of all the internal message routing, but the Go server still came out almost 5x faster than the python version. And this is from my first attempt at writing a Go program! I bet once I get a lot more solid with the language I can optimize this code a lot more.

Conclusion

I’m pretty hooked on the language. I feel its the perfect option for a python programmer that wants some speed increases and simple concurrency, without having to learn something as intense as C++. Go is supposed to get faster and faster as they improve things like the goroutines, channels, and the garbage collector, so its a great time to jump in and start learning. Its really helped me understand more formal concepts that will probably make learning C++ even easier once I decide to go back to learning it :-)

 

Jan 072011
 

Update:

I am now hosting a built package for Maya2011: MyQt4.7.4-maya2011-x64-osx-10.6.pkg
And for Maya 2012+, see: Installing pyqt4 for maya2012


Personally, when trying to run PyQt from within Maya 2009/2010 using the pumpThread method, I never had much luck. The best I ever got was the ability to bring up a dialog but not without locking up the UI, even though the pumpThread tool is meant to address that.

Anyways, when I found out Maya 2011 was rewritten based on Qt for the UI, I was really stoked. I saw the example video of being able to design a ui file in Designer, and just directly open it in a maya script, and all I could think about was designing Qt GUIs so much more easily now. Turns out that Maya 2011 didn’t actually ship with PyQt included for licensing reasons I’m sure. But it included documentation on how one could go about building PyQt for maya. Unfortunately I had tons of issues that caused maya to just crash when importing PyQt.

What I finally figured out was a mish-mash of information from the maya documention, and different forums and user groups. So I decided to make this easier on anyone having the same problems as I did, and just collect that information into one place. This process is for OSX. I’m sure most of it is probably still relevant to linux or win, except for the last parts with ‘install_name_tool’. You would just need to make sure to find the right Qt/PyQt/SIP packages for your OS.

Building PyQt4 for Maya 2011 on OSX

Update for Maya 2012

While Maya uses newer versions, it seems the versions from the 2011 install still work. But here they are anyways incase you want the newer version for 2012:


Make sure you have downloaded and installed the latest XCode from Apple. Its also included on your OSX installation disc.

Qt: Maya has a specific version of Qt built into it. This is Qt 4.5.3.
  1. Download:  qt-mac-opensource-src-4.5.3.tar.gz
  2. Extract:
  3. Build and install:
SIP: The maya docs recommend sip version 4.10
  1. Download this specific SIP:   sip-4.10.tar.gz
  2. Extract:
  3. Build and install:
PyQt4: The maya docs suggest PyQt 4.7
  1. Download this specific PyQt: PyQt-mac-gpl-4.7.4.tar.gz
  2. Extract:
  3. Set up some environment variables before building:
  4. Build and install:
  5. PyQt4 will now be installed into Maya’s python site-packages, BUT will be linked against the wrong Qt binaries. The maya docs have an annoying multi step set of commands but they don’t copy/paste nicely, so here is a for-loop you can use:

At this point you should be able to start up Maya and import and run PyQt from the script editor. You no longer need the pumpThread. Here is a test code snippet that I borrowed from here (the original had typos in it that I corrected)

It doesn’t seem like you even need the install of Qt 4.5.3 that we did at this point since we changed the links, unless you use another Qt module besides QtCore, QtGui, QtSvg, QtXml, QtOpenGL (such as QtNetwork), but this could be solved by copying over the missing libs to where Maya is expecting them. Example for copying over QtNetwork:

If you happen to have a mixed library environment like me, with more than one python lib location for code, and you see any funny errors while importing a module, just make sure that mayas python site-package is always in the front of the sys.path:

And there you have it. PyQt4 now installed in Maya 2011 under OSX.


References: