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

There is an incredibly simple way to do this, you have to clamp a point in x and y, but inside the square, while the center of the circle is between the two square border points in one of the perpendicular axis you need to clamp those coordinates to the parallel axis, just make sure the clamped coordinates do not exeed the limits of the square. Then just get the distance between the center of the circle and the clamped coordinates and check if the distance is less than the radius of the circle.

Here is how I did it (First 4 points are the square coordinates, the rest are circle points):

bool DoesCircleImpactBox(float x, float y, float x1, float y1, float xc, float yc, float radius){
    float ClampedX=0;
    float ClampedY=0;
    
    if(xc>=x and xc<=x1){
    ClampedX=xc;
    }
    
    if(yc>=y and yc<=y1){
    ClampedY=yc;
    }
    
    radius = radius+1;
    
    if(xcx1) ClampedX=x1-1;
    if(ycy1) ClampedY=y1-1;
    
    float XDif=ClampedX-xc;
    XDif=XDif*XDif;
    float YDif=ClampedY-yc;
    YDif=YDif*YDif;
    
    if(XDif+YDif<=radius*radius) return true;
    
    return false;
}