https://docs.unrealengine.com/latest/INT/Engine/Rendering/Materials/ExpressionReference/Custom/index.html Use the code from the screenshot, "return atan2(x,y);" and "return acos(x);"
Typically, an envioronment map is a set of 6 textures derived from the axis of your scene (+x, -x, +y, -y etc). engines or shaders use it as a lookup for reflection/refraction.
Hey guys! I'm building an environment based off a scene from one of my favorite books, First King of Shannara by Terry Brooks. Basically, the characters are searching for a powerful relic called the Black Elfstone in an ancient fortress called the Chew Magna, hidden in a mountainous region. (Currently I am focusing on the…