Surface area & area under curve for 3D surface plots?


Thank you for taking the time to read/respond to my post.
Suppose you have a plotly 3D surface similar to the ones shown below.
Question: What might be the best way to compare them in order to quantify their differences?

I was thinking that volume under the surface would be a good start (to look at the effect of the y axis-in this case “abundance”) on the shape of the surface. Also the surface area of of the surface might be metric. Or the ratio of the surface area to the volume.

Does anybody who is more advanced, with the source code for the plotly function / add_surface function have a way to go about calulating surface area or area under the “curve” (or surface) for these 3D surface plots?

Thanks again! I look forward to seeing your response.