To visualise the topographical distribution of electric or magnetic brain activity on the head, FieldTrip uses a family of topoplot functions. There are several styles to choose from, which determine o.a. if contour lines will be plotted on top of the color image.
Now, the default setting cfg.style = ‘both’ (with contour lines) or cfg.style = ‘straight’ (without contour lines) rely on contour or contourf, which in Matlab 2014b and later plot a set of triangles rather than one rasterised figure. This massively increases file sizes, and can cause weird artefacts when saving and viewing as pdf (elaborate rant here). Continue reading