Model a smooth cross vault

[maria.soboleva]

Hello!

I am currently working on a model of a historic gothic church. There are cross vaults where central point is higher than sides (similar to that picture https://www.researchgate.net/figure/The-geometry-of-the-Gothic-cross-vault-is-defined-by-that-of-the...). 

I tried conceptual mass, but after creating a solid form, the shape becomes segmented. As I want to apple roofs by faces to these masses, I would have to create a lot of those segmented roofs. The result looks messy. Also, it works only on relatively low-steep forms. When I try to make the form sharper (to have more difference in heights), the mass collapses: "Unable to create form element: self-intersecting or singular geometry would result."

I attached some pictures to illustrate my question. 

Does anyone have a good method for modelling this kind of vaults? Or should I use some other Autodesk product?

Thank you in advance!