fEMG facial EMG, which electrodes & where
Hi Folks. First post so please be gentle.
I have a long term project that I am working on. Essentially it will be used for character actors (say werewolves, or monsters) where the face is mostly hidden and may not correspond to a humanoid face at all.
Normally in the movies you might have a team of people handling the characters expressions and emotions for you whilst you perform the main physical movements, however in a convention or a more ad-hoc environment where you are not working to a script this becomes more difficult.
What I am looking at is to use the facial muscle of the actor and then 'parody' or replay these movements on the character's face. Say eyes moving, eyebrows up and down, maybe even use other muscles groups to control the ears. A muscles need not be linked to the same movement in the character.
Now - as the actor will be getting very hot and sweaty there will be perspiration which is conductive. How will this affect dry and wet electrodes. Currently I am looking at dry reusable electrodes for the set up.
I hope (funds willing) to buy an Arduino OpenBCI board with 8 bi-polar inputs pretty soon but I'd like to get the theoretical side down first 
Many thanks for any information
Dave
Comments
Dave
I wasnt aware of the fEMG using in gaming and marketing. Wikipedia looks like it has some decent references,
http://en.wikipedia.org/wiki/Facial_electromyography
And you've likely seen these as well,
http://facialemg.com/
http://facialemg.com/research.html even more papers
http://www.gandrllc.com/solutions/content-assessment/emotional-response-analysis/
Their patent, http://www.google.com/patents/US20030032890
The photos on Chip's blog are EKG type foam electrodes. Patent shows much smaller diameter. Probably more along these lines,
http://bio-medical.com/products/gs26-pre-gelled-disposable-semg-electrodes-300-pack.html
William
This is an excellent reference I found too
http://csl.anthropomatik.kit.edu/downloads/GibertPruzinecSchultzStevens_OZCHI09_HCIwithEMG.pdf
With 8 electrodes they were able to get enough information to get an avatar to display the same emotion. Where they are applying the expression to the avatar they are unclear whether their process is
fEMG -> expression/emotion analyser -> avatar emotion
or
fEMG -> Avatar facial
For myself as I am not interested in the emotional context, rather the muscle distortion I can use the second which would be fEMG to servo response. Although to get a gross emotional indication (sad, happy, angry, passive, concerned) would assist in running preprogrammed sequence to set up the characters face onto which the finer details can be adjusted.
For example - a werewolf with movable ears that cannot be controlled as there are no corresponding muscle groups in humans
Happy - ears are up and forward
Sad - ears are down and splay to sides
Angry - ears are swayed back
etc.
The tail can also be included in the above.
Previously I was looking at using SimpleCV and a webcam to pick up the mouth's shape but this could prove to be easier. I could also preset electrodes onto insulated backing to assist in attaching them quickly. And maybe even a headband for the upper face muscles for eyebrows. In the end one does not want to spend several hours doing electrode placements for 30 mins of acting.
Many thanks for replying
Dave