Means of surface shape like flat, smooth or curvy shapes in (linear or constant output) sugeno, mamdani type and com[pare these results through which parameters.
when I use the surface viewer of Matlab Fuzzy toolbox, i limit it to only 2 inputs and 1 output thus becoming a 3D system. With that, interpreting the surface that you created is simply a 3D plot of an algebraic expression. Get x and y and project it vertically to get z.
I think you may like to read this Matlab doc below to help you understand what a surface shape means from your running system outputs. Hope this helps.