How to detect terrain's mesh normals at given point?

Hey, quick question, how do I know the normals of a given point on the terrain, to know wich texture must be painted? (grass or cliff).

I did a quick debug code where it should detect the normals at the position of the camera, but when I move around the map the normals vector stays the same (0,1,0), even passing by mountains and stuff.

Here the code, I used terraindata.getInterpolatedNormal. Shouldn't that do it?

GUI.Label(new Rect(10,10,500,500), "Camera position: " + cameraPlayer.transform.position);

GUI.Label(new Rect(10,20,500,500), "Normals at CamPos: " + terrain.terrainData.GetInterpolatedNormal(cameraPlayer.transform.position.x, cameraPlayer.transform.position.z));