Comment by corysama

Classic SSAO is very similar to performing an "unsharp mask" based on the depth buffer. This has been proposed "a simple and efficient method to enhance the perceptual quality of images that contain depth information" in the paper "Image Enhancement by Unsharp Masking the Depth Buffer" which came out a year after SSAO was published by Crytek.

https://www.uni-konstanz.de/mmsp/pubsys/publishedFiles/LuCoD...