My name is Peter April. For the past fifteen years, I have been writing
software for vision researchers. One of my programs which has gained
popularity in many vision labs is called “Pixx”. Pixx allows vision
researchers to create dynamic visual stimuli and run experiments with
them on a Macintosh computer. Here is a very brief summary of what some
vision researchers are currently doing with Pixx:
1) Pixx can create regions on the video screen:
-Rectangular
-Oval
-Arc segments
The screen can have multiple regions of different dimensions. Regions
can appear and disappear during an animation.
2) Pixx then fills the regions with different patterns:
-Checkerboard
-Drifting gratings (square/sine/triangle wave)
-Radial patterns
-Concentric circles
-Looming patterns
-Drifting dots
-Random noise
-Subjective contours
-Symmetrical textures
-Stereoscopic viewing images
-Arbitrary clip-art images like PICTs
Multiple patterns can be superimposed in a single region, creating
plaids, second order motion stimuli, or masks. Regions can drift,
flash, contrast reverse, and otherwise animate during presentation.
3) Pixx can then run an experiment using your animations as stimuli.
Experiments can present fixed sequences of animations, or randomize
conditions. Response data can be collected and analyzed. Adaptive
paradigms like PEST and method of adjustments can even modify your
stimuli during testing.
4) Pixx can be interfaced to external hardware, allowing evoked
potential data acquisition to be correctly synchronized with stimulus
onset.
There is a recent version of Pixx available for free download at:
http://www-psychology.concordia.ca/department/CVLab/Rick.html#Pixx
The downloaded folder includes some basic introductory and tutorial
information. Please feel free to give it a try.
I am currently preparing for a complete rewrite of the Pixx program in
order to add many more features which have been requested by the growing
number of Pixx users. In order to make the program as useful as
possible to a wide range of users, I am seeking the advice and support
of the vision research community. If you use visual stimuli in your
research, I would like to know what kind of imagery you use so that I
can incorporate it into Pixx. If you have some experiments which you
would like to run, but have not yet been able to due to a lack of
supporting software, then I would especially like to discuss your
requirements. Please email me with any ideas or questions you may have.
Thank you,
-Peter April