It's part of the rendering engine and the program itself that is used to create the levels.

It's probably called "alpha tiling", lol. I'm not for sure myself.

A lot of games come with "editors" in which you create your own levels. The editors included with the Unreal games are pefectly capable of editing together a level comparable with what the company makes.

In Bryce, I have made 3 terrains, with 3 seperate DTE mats. And, the terrains could be driven with 3 seperate alpha maps, giving them areas of visibility. It was not an exact science at all, it took experimenting and luck, but the end result has the ability to look really cool. It would just take some practice to get there.

AgentSmith

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