Recently after playing hours of Minecraft (and generating block volumes), a question popped up in my head: Is it possible to easily (by hand in a reasonable amount of time) determine the surface area of an arbitrary function? For instance, if you were to take the function $y=x^2$, and move it onto a graph with discrete coordinate values (with non-integer function values being rounded accordingly - something like $\text{Int}(y)=x^2$ for $[\text{Int}(a),\text{Int}(b)]$ ? Extending that further, like here would it be possible to find the volume of some equation or solid of revolution and in addition the surface area? In other words, could you calculate the area of a function using the rectangle method with midpoint approximation and equal width rectangles?
If these are not possible, can one find some sort of approximation of this area/volume more accurate than that of the integral it seems to represent? Thanks.