Freeform structure and the Beijing National Stadium

[Norahh]

Hi, guys. I am doing researching about freeform structures. And some articles said that double curved is free form, some said both single curved and double curved are free form. What exactly is the definition? And is the Beijing National Stadium as shown in the picture freeform structure?

 

[BAretired]

My understanding of a freeform structure is one that does not conform to a regular shape. Circular domes, elliptical domes and hyperbolic paraboloids are examples of doubly curved surfaces but they are not freeform. Cylindrical shells are single curved surfaces but they are not freeform.

A freeform structure could have single or double curvature but its coordinates are arbitrarily selected by an architect on the basis of aesthetics and cannot be expressed mathematically as a continuous function.

I'm not sure precisely what its shape is but I don't consider the Beijing National Stadium to be freeform. There are many images of freeform structures on the internet.

BA