Shader Graph - Check angle of face

Hey gang, I am building a river shader and i have worked out how to get a tiling texture to work. so my river looks ok, but i want it to speed up or slow down based upon the angle of the river, and i want it to turn into a waterfall if i make it quite steep.

what node should I use in order to get the angle of the polygon? I feel once i get this i should be able to work out the rest

 

I'm not expert in shaders yet but try to search for "normal". I mean face normal, not normal map.

 

I managed to solve it. I used a Normal Vector node, connected to an Absolute node and then multiplied it by itsself.

This gives you x y and z directions from your mesh. As I was only needing the Y direction I used a split node to get the G channel and i can then plug that into a blend node or wherever else you need it.

 

Hey I know this post is old, but I just have to say however different your end goal was to mine, I find this extremely helpful in fixing a custom triplanar blend node to work better, so thank you for posting this!

 

Thank you for posting the answer. It would be cool if someone could explain why we have to multiply the absolute normals by themselves. I can't understand that part.