The shaders are heavier, that's why I implemented it differently, sacrificing some minor effects. O'Neal's shaders had many difficult corner cases so I was constantly looking at how to make it better.
As for his other work, there can be only some generic similarities. Water is done differently; he can't do shore waves that way and I wanted them or nothing
Vector roads are entirely different implementation-wise from the ones in Outerra, but that mainly relates to different architectures. Later he also added some fractal refinement inspired by Outerra, so who knows maybe it's all converging into the same thing