Determining slope in shader

Question

So, I'm trying to figure out what the slope is in a shader so I can make changes to albedo based on that.
I assume I need to do something with the normal, but I'm really not sure what.

Lalalalage

Answer 1

The slope angle is inverse cosine of the dot product of normal vector and up vector. For most things you can use the dot product directly without calculating the inv cosine. It'll vary in range 0-1.

Overdevelop

Answer 2

works a treat, thank you!

Lalalalage