In the documentation for the surf command it is stated that for faceColor = 'flat', "The color value at the first vertex of each face (in the positive x and y directions) determines the color for the entire face."
Paired with the accomanying drawing, I completely understand how this work for a rectangular grid. However, I would like to know what exactly is the 'first vertex' in case of a non-rectangular grid. I'm trying to make a polar plot with surf, and this is vital information.
PS, I tried to find out through the source of surf, but it seems like the magic happens in a .p file.