The general term for these structures in 3-d is a space frame.
"Just making a triangle array" is a pretty good starting point, because three bars forming a triangle make a rigid structure without any bracing at the corners, unlike four bars forming a rectangle which can be "squashed" out of shape.
Another key to making a stiff lightweight structure is to make it curved in both directions (i.e. not like a cylinder or a plane), so that effectively you have groups of four bars forming tetrahedra. The curved structure works the same way as a dome.
If you want to study designing something like this, you could start with the same idea in two dimensions, called a truss. Trusses are a very common engineering design for the roof supports in buildings, and also for bridges, tower cranes, etc.
To make a space frame which is cheap and easy to assemble, you need to make the bars with a few standard lengths and meeting at the same angles, rather than every bar and every joint being different. Of course a computer aided design can have every part different if you want, but the manufacturing and assembly costs will be higher.
You might want to look at polyhedra (including "semi-regular" polyhedra, not just the five "Platonic regular solids") where all the edges are the same length, and buckyballs which have similar properties. In particular, there are a few deltahedra where all the faces are equilateral triangles but the complete object does not have a "regular" shape. The regular polyhedra were studied by the ancient Greek mathematicians, but the irregular shaped deltahedra were not discovered until nearly 2000 years later - most likely simply because nobody bothered to look to see if such a thing could exist.
Google any of the terms in bold type for more information.