public Triangle ScaleByDistance(double distance)
{
Point3d middlePoint = Vertices.ToArray().MidPoint3d();
Vector3d vec = middlePoint.Subtract(V1);
vec = vec.GetUnitVector();
Point3d p2 = V1.Add(vec.Multiply(distance));
Vector3d vec2 = middlePoint.Subtract(V2);
vec2 = vec2.GetUnitVector();
Point3d p3 = V2.Add(vec2.Multiply(distance));
Vector3d vec3 = middlePoint.Subtract(V3);
vec3 = vec3.GetUnitVector();
Point3d p4 = V3.Add(vec3.Multiply(distance));
Triangle result = new Triangle(p2, p3, p4);
return(result);
}