How to track multiple fingers on a touchscreen

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Hi everyone,

I'm hoping people could have some idea about this problem I have. We are designing an experiment that requires the subjects to place one finger in each of the two boxes shown on a touchscreen. So we need to check and make sure that the fingers are within the boxes. However using GetMouse() doesn't seem to help, because the mouse position reported seem to behave very strangely.
I'm running Windows 7 64bit and Matlab 2013b. I don't really understand the doc of GetMouse() that says it only reports 'the unified state of all mice'. I get it that it doesn't report the positions of the two fingers simultaneously, but I was hoping that it may be reporting the 'average position' of the two, in which case a program is still possible to be written to do the job. But it doesn't seem to be the case, or perhaps the touchscreen device itself is doing weird things.
I know there's the option to go to Linux but configuring Psychtoolbox in Octave and Linux is quite tiresome in my experience. I honestly haven't succeeded completely in that route yet.
Thanks to you in advance!

--
Marshall Zhiyuan Wang

graduate student at University of Illinois, Urbana-Champaign
Department of Psychology, Division of Visual Cognition and Human Performance
Office: Room 514, 603 East Daniel Street, Champaign
Mobile: +1 （217）898-0846
2
---In psychtoolbox@yahoogroups.com, <zhiyuanwang42@...> wrote :

Hi everyone,

I'm hoping people could have some idea about this problem I have. We are designing an experiment that requires the subjects to place one finger in each of the two boxes shown on a touchscreen. So we need to check and make sure that the fingers are within the boxes. However using GetMouse() doesn't seem to help, because the mouse position reported seem to behave very strangely. 
I'm running Windows 7 64bit and Matlab 2013b. I don't really understand the doc of GetMouse() that says it only reports 'the unified state of all mice'. I get it that it doesn't report the positions of the two fingers simultaneously, but I was hoping that it may be reporting the 'average position' of the two, in which case a program is still possible to be written to do the job. But it doesn't seem to be the case, or perhaps the touchscreen device itself is doing weird things. 

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GetMouse treats all mice on Windows as one mouse. There's one mouse-cursor and any connected mouse or mouse like device will move that cursor around. Iow. it doesn't average or such and is useless for your purpose unless you'd find a touchscreen which does the averaging you want due to a hardware limitation.

I personally don't have any plans or motivation to ever add multi-touch support to PTB for Windows or OSX.

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I know there's the option to go to Linux but configuring Psychtoolbox in Octave and Linux is quite tiresome in my experience. I honestly haven't succeeded completely in that route yet. 
Thanks to you in advance!

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Poor you! I already feel sorry for you. Maybe explaining what exact tiresome steps you have taken and where you got stuck might have helped, but that's probably too tiresome?

That said, i don't know how well Linux-PTB would work for your application. Linux PTB can address multiple mice, touch devices etc. independently, after some deeply tiresome configuration of course. This works very well with digitizer tablets, as tested on some Wacom tablets, using multiple tools simultaneously to control multiple mouse pointers or GetMouse inputs.

Multi-touch is something slightly different and requires different treatment in the software, cfe.:

Multi-touch support landing in X [LWN.net]

 



We support Multi-pointer-X, but not multi-touch. In practice what you want to do may still work in a slightly hacky way, i seem to remember it worked ok'ish on my Nexus-7 tablet, after some tiresome configuration and tinkering, of course.

I will add multi-touch support to Linux PTB at some point, once i can see serious interest in users. But so far only two people ever installed PTB for Linux tablets, so this is not a super urgent high priority atm.

-mario

--
Marshall Zhiyuan Wang

graduate student at University of Illinois, Urbana-Champaign
Department of Psychology, Division of Visual Cognition and Human Performance
Office: Room 514, 603 East Daniel Street, Champaign
Mobile: +1 （217）898-0846