[FieldTrip] head model mat contains only NaN values

[gj]

Hi,

Just to keep questions-answers in the same thread, the problem I had 
with only NaNs in the head model appears indeed to be because of the 
internal intersecting mesh plans in the "scalp" (at least the problem 
disappeared once I got the scalp mesh not to intersect). After much 
digging, I found these previous posts

http://mailman.science.ru.nl/pipermail/fieldtrip/2014-January/007433.html
http://mailman.science.ru.nl/pipermail/fieldtrip/2013-March/006365.html

from Gregor who noticed that the finer the mesh, the more likely self 
intersections occur. He also suggested using om_check_vol() on the 
prepare mesh output to check for intersections, but I couldn't get it to 
work (om_check_vol expects a "skin" structure?) so relied on visual 
inspection with ft_plot_mesh.

After much persistence with playing with different cfg.numvertices 
values for ft_prepare_mesh (for those wondering I ended up specifying 
330 vertices for the "scalp" of an MRI with head+neck), I was able to 
get a mesh with no self-intersections and was able to calculate a head 
model with more meaningful values.

g