Hello all,
DUNEuro uses the first electrode as the reference for the forward computation, therefore it sets all the values to zeros for this electrode.
As far as I know, the same process is done with ft-simbio.
Then for the inverse computation, the average reference is applied by Brainstorm for this matrix.
If you want to use the Gain matrix outside of Brainstorm, you can either use the average re-referencing or re-reference the Gain matrix to your reference electrode, just be subtracting the value of your reference from all the electrodes (moving the zeros line to the new reference).
Yes, Duneuro is much faster since it uses a faster solver than the one implemented within ft_SimBio,
adding to @Francois comments, if you want to compare you need to have the same parameters and the same head model. ft_simbio has only the Venant source model and the parameters are fixed, the difference is in the source code, Duneuro is Cpp based and SimBio is a mixture of C and Fortran, and there are some differences in the solvers. Therefore you can find slight numerical differences.
I'm not sure that the ft-code version of this workshop is available at this time.
But I recommend reading the tutorials.
Best,
Takfarinas