How can I make the material move the object in the direction of the normal?

Development Rendering
1

I have some trees, and i wanted to have some kind of wind blowing into them. To achieve this I used the same method I used for the grass: A panner and a sine wave in the World Position Offset. This is the material I used:

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Sem título.png1309×704 157 KB

The problem is:
The leaves (a bunch of planes with an opacity mask) will only move perfectly sideways. How can I make them move in the direction of their normal or their tangent?

2

You’re only putting a scalar into world position offset. Multiply that value by VertexNormalWS.