Vec2D Vec2D::projection(Vec2D const& other) const
{
Vec2D direction = other.unit();
return direction.scalei(dot(direction));
}
// n.projection(m) = m, m.reverseProjection(n.unit()) = n
Vec2D Vec2D::reverseProjection(const Vec2D &other) const
{
Vec2D nu = other.unit();
float l = length();
return nu.scalei(l / nu.dot(scale(1.0f/l)));
}