I’ve seen old techniques where people used models with different shaders to make pieces of the terrain transparent and then use the same technique for getting rid of collision. I was wondering if there is a new way of putting holes in the terrain?
There aren’t a whole lot of ways to create holes in unitys terrain at the moment. The old way you are speaking of by using shaders with certain alpha settings is about the only way to make the appearance of a hole in unity. As for passing through the hole you would need some sort of entrance and exit triggers to disable that area of the return as you pass through. Rtp does agreat job of this as well as other assets in the store.
Relief terrain pack does exactly what you want.