Circle-Rectangle collision detection (intersection)

Question

How can I tell whether a circle and a rectangle intersect in 2D Euclidean space? (i.e. classic 2D geometry)

Answer 1

1. do a pre-check whether a circle fully encapsulating the rectangle collides with the circle.
2. check for rectangle corners within the circle.
3. For each edge, see if there is a line intersection with the circle. Project the center point C onto the line AB to get a point D. If the length of CD is less than radius, there was a collision.

    projectionScalar=dot(AC,AB)/(mag(AC)*mag(AB));
    if(projectionScalar>=0 && projectionScalar<=1) {
        D=A+AB*projectionScalar;
        CD=D-C;
        if(mag(CD)