[Sidefx-houdini-list] Real Time Applications

david at sidefx.com david at sidefx.com
Mon Oct 15 11:57:39 EDT 2007


The original post mentions the use of an EEG.  I had a IBVA single channel
system connected to Houdini's CHOPs or CHOPs in Touch and it worked very
well.  Once you digitize the brainwaves the amplitudes can be quite low -
in the microvolt range so you can scale these up either in software or in
hardware (by adding on a variable opamp).  All of these decisions should
support your purpose for designing such a system.  Once the brainwave data
is in CHOPs I found that I was able to extract meaning by running it
through the Spectrum CHOP to perform an FFT analysis to view and separate
out the frequency bands assosciated with thought: alpha, beta, theta, etc.
 At this point you can set thresholds with a Trigger CHOP that can trigger
the execution of scripts, toggling switches, or simply map the live signal
to any parameter in Houdini.

Now with Houdini's built-in PYTHON support you should be able to get this
data in/out easily.  Be sure to match the sample rate in the CHOPs you are
using with the sample rate of your hardware EEG device.  All of the above
can also be done with TOUCH which has been optimized for realtime use.

If you have the opportunity look for Rosenboom's book (out of print)
BIOFEEDBACK AND THE ARTS for some interesting discussion on work done in
this field dating back to the 1970s.

David

> I'm a Touch user, and yeah i reckon it'd do the trick perfectly. great for
> realtime stuff and quite flexible interfacing with various applications
> and
> hardware
>
> Check it
>
> Jason
>
> On 10/15/07, Mark Story <mstory at xion.org> wrote:
>>
>> Hi Grav,
>>
>> I've been doing real time data acquisition for a billion years including
>>   this type of instrumentation visualization.  The usual issues are
>> always at play, sampling rate, data throughput, propagation delay, etc.,
>> it can be impossible to wrap it up in Houdini, often one has to write
>> custom code to make things work.
>>
>> You can also try Touch, Houdini's real time counterpart:
>> http://derivativeinc.com/home/home.asp
>>
>> It only runs on Windows unfortunately.
>>
>>
>> Mark
>>
>>
>>
>> > Hey all,
>> >    Here is the question.  Are any of you using Houdini for any real
>> time
>> > applications.  I always used it for things to go to video, so resource
>> > usage and such was never really an issue so long as render times were
>> > reasonable and I didn't run out of memory.  However, I am in the
>> middle
>> of
>> > building an EEG which will be used as the hardware end for an
>> interactive
>> > biofeedback installation piece.  If I have too, I suppose I can code
>> real
>> > time particles to do things based off of numeric values interpolated
>> from
>> > the signals.  I've done it before for a large scale touch screen using
>> > Processing, but it was a real bear to do and managing an illusion of
>> depth
>> > was VERY challenging.  Is there anything in Houdini which is capable
>> of
>> > handling real time input and output?  If so, where should I be looking
>> and
>> > self teaching.
>> >
>> > Grav
>> >
>> >
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