circle line intersection java
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class CircleLine {
public static List<Point> getCircleLineIntersectionPoint(Point pointA,
Point pointB, Point center, double radius) {
double baX = pointB.x - pointA.x;
double baY = pointB.y - pointA.y;
double caX = center.x - pointA.x;
double caY = center.y - pointA.y;
double a = baX * baX + baY * baY;
double bBy2 = baX * caX + baY * caY;
double c = caX * caX + caY * caY - radius * radius;
double pBy2 = bBy2 / a;
double q = c / a;
double disc = pBy2 * pBy2 - q;
if (disc < 0) {
return Collections.emptyList();
}
// if disc == 0 ... dealt with later
double tmpSqrt = Math.sqrt(disc);
double abScalingFactor1 = -pBy2 + tmpSqrt;
double abScalingFactor2 = -pBy2 - tmpSqrt;
Point p1 = new Point(pointA.x - baX * abScalingFactor1, pointA.y
- baY * abScalingFactor1);
if (disc == 0) { // abScalingFactor1 == abScalingFactor2
return Collections.singletonList(p1);
}
Point p2 = new Point(pointA.x - baX * abScalingFactor2, pointA.y
- baY * abScalingFactor2);
return Arrays.asList(p1, p2);
}
static class Point {
double x, y;
public Point(double x, double y) { this.x = x; this.y = y; }
@Override
public String toString() {
return "Point [x=" + x + ", y=" + y + "]";
}
}
public static void main(String[] args) {
System.out.println(getCircleLineIntersectionPoint(new Point(-3, -3),
new Point(-3, 3), new Point(0, 0), 5));
System.out.println(getCircleLineIntersectionPoint(new Point(0, -2),
new Point(1, -2), new Point(1, 1), 5));
System.out.println(getCircleLineIntersectionPoint(new Point(1, -1),
new Point(-1, 0), new Point(-1, 1), 5));
System.out.println(getCircleLineIntersectionPoint(new Point(-3, -3),
new Point(-2, -2), new Point(0, 0), Math.sqrt(2)));
}