although you can replace triangular graphics with basic curved surfaces on each triangle deduced from basic triangular curve rules you don't actually have to use the simplest linear progression in order to deduce the curve surface rules.
You can use the same rule or different rules for each of the sides.
such a thing in it's usual form will look like a diagonal line on a graph this line could be curved or any thing so long as the starting point is at radius 1 and the other point is at radius 2.
Ok so if you use advanced progression lines what extra features can you add to your graphics.
well you could add subtle bumpy skin a make the curve more straight with some bumpiness for more realistic walls.