Terrain Angle Check.

Find the normal of the terrain under that point.

Then check if

n.y / sqrt(n.x^2 + n.z^2) > tan60

Basically that is the tangent of the angle of the normal with the horizontal.

Notice that a point is not going to have a direction on a terrain. You can allways look at it from a lot of diffrent directions giveing it a diffrent angle.

What you need is where the character is and where he is trying to go; a point and a direction. Then you can add the length of the movment to the point and find out what that height will be at that point. Useing the two heights you can find out what the angle is.