--- /dev/null
+:date: 2011-xx-xx 0:00:00
+:tags: neuroscience, software, opensesame, sebastiaan mathot
+:author: Sebastiaan Mathôt
+
+OpenSesame and back-end independence
+====================================
+
+I suspect that many of you will not be familiar with me or my software, so
+let's start with a brief introduction. My name is Sebastiaan Mathôt. I'm the
+lead developer of OpenSesame, a graphical tool for creating psychological and
+neuroscientific experiments.
+
+About OpenSesame
+----------------
+
+The reason that I started working on OpenSesame, aside from the inherent
+pleasure that a geek like myself derives from developing software, was my
+dissatisfaction with the tools that were available. Not that there's a shortage
+of experiment building software, not at all. And for people with reasonable
+programming skills there are many viable options: MatLab/ Octave in combination
+with the Psychophysics Toolbox, Python in combination with VisionEgg or
+PsychoPy, to name but a few (all of these are, incidentally, available through
+NeuroDebian). But for people with relatively modest programming skills, such as
+most students doing a Bachelor's or Master's project, there aren't that many
+options. In my experience, people will generally end up using a proprietary
+program, such as E-Prime, Inquisit, or what have you. These offer a reasonably
+intuitive graphical interface, but at a price. First, these packages are
+expensive and, due to licensing restrictions, people are frequently unable to
+install them on their personal computers. Second, they are limited in their
+functionality and in their interoperability with other software.
+
+.. figure:: pics/blog/opensesame_stimulus.png
+
+ One of the unique features of OpenSesame is the ability to draw your
+ stimuli. You can combine this what-you-see-is-what-you-get approach with
+ scripting, to easily create flexible stimulus displays.
+
+Therefore, I wanted to develop a graphical environment for building
+experiments, centered around the Python programming language. The idea was to
+give users the type of comprehensive graphical interface that they have come to
+expect from proprietary packages, but for free, and without taking away any of
+the power that Python has to offer. And, almost a year, 12 public releases, and
+more than 10,000 downloads later, the result is OpenSesame!
+
+Back-end independence
+---------------------
+
+For this post, I was asked to write about one of OpenSesame's features in
+particular: back-end independence. This may sound a bit technical and boring,
+but it's not. Well... maybe a little boring. In fact, it should be a little
+boring, because it's a feature that you're not supposed too notice, unless you
+need it.
+
+So what do I mean by "back-end independence"? Experiments are all about
+presenting stimuli. Most often visual stimuli on a computer display, sometimes
+sounds, tactile stimuli, etc. From the perspective of a programmer, there are
+many ways to present such stimuli. Put differently, there are many programming
+libraries that you can use.
+
+For example, if you want to write a program that controls a computer display,
+you can use a Python library called PyGame. PyGame has been designed with
+video-games in mind, but, experiments being conceptually so similar (although
+not typically as entertaining), it is also well suited for creating
+experiments. For this reason, I initially designed OpenSesame around PyGame.
+
+This seemed like a good idea at the time, but there was a huge drawback. If
+people wanted to use OpenSesame, they were forced to use PyGame as well. It was
+a package deal, so if PyGame didn't support a particular feature, neither did
+OpenSesame. That wasn't very nice. And it also wasn't necessary, because there
+was nothing in OpenSesame that inherently required PyGame. It was just an
+arbitrary design choice that I had made at the outset.
+
+So I decided to decouple the "back-end" (i.e., all the functions that had been
+handled by PyGame up to that point) from the rest of OpenSesame. This means
+that the user can now choose which back-end he or she wants to use for
+controlling the display etc. Importantly, OpenSesame continues to function in
+the same way, regardless of which back-end is selected. For users who don't
+care or know what a back-end is, let alone which back-end they prefer, PyGame
+still serves as a default.
+
+.. figure:: pics/blog/opensesame_backend.png
+
+ You can easily select your favorite back-end using the graphical interface.
+ The same experiment can be run, (usually) completely unmodified, using any
+ of the three available back-ends.
+
+So what's the upshot of all this? Right now, the most direct benefit is that
+you can use OpenGL and PsychoPy in your OpenSesame experiments. PsychoPy in
+particular provides lots of functions (drawing Gabor patches etc.) that are
+very convenient when creating experiments. Previously, users couldn't use
+these, because PsychoPy doesn't play nice with PyGame (even though it actually
+uses, or can use, PyGame under the hood). Now they can, so that's a definite
+plus. And in the future I may add more back-ends, depending on popular demand.
+For example, VisionEgg is another library for creating experiments. VisionEgg
+is quite popular and could probably be used as a back-end as well.
+
+This means that users of OpenSesame now have both a comprehensive graphical
+interface and powerful programming libraries at their disposal. They can
+choose. Most of the experiment can usually be created using the GUI, which is
+especially appealing for the less tech-savvy among us. But, for more
+complicated parts, Python scripting can be used and, consequently, users have
+access to a wide range of libraries.
+
+I think that OpenSesame's back-end independence is a nice example (one of many,
+I hasten to add) of how free software can work together. If it hadn't been
+possible to use PsychoPy and OpenGL in OpenSesame, I would have probably ended
+up duplicating lots of functionality. That would have been very time consuming.
+Time that I have now spent on refining other parts of OpenSesame, unique parts
+and not simply duplicates of existing functionality.
+
+And ultimately, I believe that this type of interoperability is why free
+software will continue to grow.
+
+Links
+Cogsci.nl <http://www.cogsci.nl/>
+OpenSesame <http://www.cogsci.nl/opensesame>
+
+
projects / neurodebian.git / commitdiff
