Flatmaps get some advantage from the convexity shading, but you can turn it off or otherwise control it. The easiest way to turn it off is by tapping the 'b' key to turn off the background coloring. You can also make the convexity less obtrusive by using a more subtly shaded gray scale like ngray20. Switch Dset to Convexity. Then select the colormap with the Cmp button on the right side of the surface object controller. You can set that permanently in your .sumarc file in your home directory by setting the variable SUMA_ConvColorMap = ngray20 .