I've seen loads of gorilla exhibits in my lifetime, and I think that Riverbanks Zoo has perhaps the densest vegetation of any gorilla enclosure ever. However, the zoo only has two silverbacks in the lush exhibit, and on my visit I didn't see either of them.
I know that you have since visited this South Carolina zoo, but besides the mesh viewing area there is also an unobstructed series of viewpoints as well as a massive set of windows:
