[dghlsakjg]

It’s a trick question sorta.

You can’t make a compound curve out of sheet material. Drywall can bend in a single axis only. If you add a second axis (compound curves) it won’t really work. Think about trying to drywall a sphere. The best you can do is a high poly sphere.

[lnsru]

It’s not a single sheet. It’s multiple sheets covered in gypsum shell. More sculpture than drywall. Relative worked for riches, egg and bells were his projects 25 years ago. It’s just many many hours designing it and even more sanding to get perfect shape. There are now 3D printers for such projects: https://www.voxeljet.com/3d-printing-solution/sand-casting/ Since it’s cheap and fast today riches lost interest.

[ChoGGi]

That's what the mudder is for ;)