def center_of_3points_arc(point1: 'Vertex', point2: 'Vertex', point3: 'Vertex') -> Vector:
"""
Calc center point of 3 point arc. ConstructionCircle is defined by 3 points on the circle: point1, point2 and point3.
"""
ray1 = ConstructionRay(point1, point2)
ray2 = ConstructionRay(point1, point3)
midpoint1 = lerp(point1, point2)
midpoint2 = lerp(point1, point3)
center_ray1 = ray1.orthogonal(midpoint1)
center_ray2 = ray2.orthogonal(midpoint2)
return center_ray1.intersect(center_ray2)
def _get_text_insert_point(self, section: int) -> Vector:
""" get the dimension value text insert point """
point1, point2 = self._get_section_points(section)
dist = self.prop('height') / 2. + self.prop('textabove')
return lerp(point1, point2) + (self.normal_vector * dist)