   calculate angle between two vector
  Hy.I would adapt my mesh character with the angulation of the terrainmodel.I have a normal vector, that is the normal of a plane of my terrain model.I would to calculate the angle between my model and the terrain for rotate my character.But how i find my character orientation normal?Thanks   
  If your character is something like a person that is always upright, the character 'normal' will simply be a vertical unit vector cn, like [0 1 0]. The angle between this and the terrain normal tn=[nx ny nz] will then be theta from the equation:cos(theta) = cn * tn / (|cn| * |tn|) = (ny) / (sqrt(nx^2+ny^2+nz^2))Does this make sense?   