Function charts::utils::calculate_control_points

pub fn calculate_control_points(
    p1: Point<f64>, 
    p2: Point<f64>, 
    p3: Point<f64>, 
    t: f64
) -> (Point<f64>, Point<f64>)

Calculates the controls for [p2] given the previous point [p1], the next point [p3], and the curve tension [t];

Returns a list that contains two control points for [p2].

Credit: Rob Spencer (http://scaledinnovation.com/analytics/splines/aboutSplines.html)