Java Circle-Circle Collision Detection

问题

Here is the circle class:

public class Circle {
    private double radius;

    private double x;
    private double y;
}

How can I tell if two objects from this class (circles) are colliding?

P.S. Can you use the method that avoids taking a square root?

回答1:

double xDif = x1 - x2;
double yDif = y1 - y2;
double distanceSquared = xDif * xDif + yDif * yDif;
boolean collision = distanceSquared < (radius1 + radius2) * (radius1 + radius2);

回答2:

dx = x2 - x1;
dy = y2 - y1;
radiusSum = radius1 + radius2;
return dx * dx + dy * dy <= radiusSum * radiusSum; // true if collision

The link from @instanceofTom in the comments is better... with pictures.

回答3:

The circles will touch when the distance between their centres is equal to the sum of their radii, or collide when the distance is less.

Since we are using absolute distance, it is Ok to compare the square of the distance between centres with the square of the sum of the radii.

回答4:

Here's the updated Java solution:

public boolean hasCollision(Circle circle){
    double xDiff = x - circle.getX();
    double yDiff = y - circle.getY;

    double distance = Math.sqrt((Math.pow(xDiff, 2) + Math.pow(yDiff, 2)));

    return distance < (radius + circle.getRadius());
}

来源：https://stackoverflow.com/questions/8566336/java-circle-circle-collision-detection