Making mountains

One of the main features to get a mountain model believable is terrain erosion, which is the simulation of how water would erode a terrain to create valleys physically over the years. For Mountains, I used the approach taken by Cartesian Caramel here to get a similar erosion result visually, basically by calculating the shortest paths in a grid. So in the end, this looked like a reasonable faster technique to use rather than a slow simulation that takes a lot of time.