Line circle intersection: Difference between revisions
Added Java Solution
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Intersection: Circle (4.0,2.0) 5.0 and Segment (7.0,4.0) (11.0,18.0): [(7.46,5.61)]</pre>
=={{header|Java}}==
<lang java>import java.util.*;
import java.awt.geom.*;
public class LineCircleIntersection {
public static void main(String[] args) {
try {
demo();
} catch (Exception e) {
e.printStackTrace();
}
}
private static void demo() throws NoninvertibleTransformException {
Point2D center = makePoint(3, -5);
double radius = 3.0;
System.out.println("The intersection points (if any) between:");
System.out.println("\n A circle, center (3, -5) with radius 3, and:");
System.out.println("\n a line containing the points (-10, 11) and (10, -9) is/are:");
System.out.println(" " + toString(intersection(makePoint(-10, 11), makePoint(10, -9),
center, radius, false)));
System.out.println("\n a segment starting at (-10, 11) and ending at (-11, 12) is/are");
System.out.println(" " + toString(intersection(makePoint(-10, 11), makePoint(-11, 12),
center, radius, true)));
System.out.println("\n a horizontal line containing the points (3, -2) and (7, -2) is/are:");
System.out.println(" " + toString(intersection(makePoint(3, -2), makePoint(7, -2), center, radius, false)));
center.setLocation(0, 0);
radius = 4.0;
System.out.println("\n A circle, center (0, 0) with radius 4, and:");
System.out.println("\n a vertical line containing the points (0, -3) and (0, 6) is/are:");
System.out.println(" " + toString(intersection(makePoint(0, -3), makePoint(0, 6),
center, radius, false)));
System.out.println("\n a vertical segment starting at (0, -3) and ending at (0, 6) is/are:");
System.out.println(" " + toString(intersection(makePoint(0, -3), makePoint(0, 6),
center, radius, true)));
center.setLocation(4, 2);
radius = 5.0;
System.out.println("\n A circle, center (4, 2) with radius 5, and:");
System.out.println("\n a line containing the points (6, 3) and (10, 7) is/are:");
System.out.println(" " + toString(intersection(makePoint(6, 3), makePoint(10, 7),
center, radius, false)));
System.out.println("\n a segment starting at (7, 4) and ending at (11, 8) is/are:");
System.out.println(" " + toString(intersection(makePoint(7, 4), makePoint(11, 8),
center, radius, true)));
}
private static Point2D makePoint(double x, double y) {
return new Point2D.Double(x, y);
}
//
// If center of the circle is at the origin and the line is horizontal,
// it's easy to calculate the points of intersection, so to handle the
// general case, we convert the input to a coordinate system where the
// center of the circle is at the origin and the line is horizontal,
// then convert the points of intersection back to the original
// coordinate system.
//
public static List<Point2D> intersection(Point2D p1, Point2D p2, Point2D center,
double radius, boolean isSegment) throws NoninvertibleTransformException {
List<Point2D> result = new ArrayList<>();
double dx = p2.getX() - p1.getX();
double dy = p2.getY() - p1.getY();
AffineTransform trans = AffineTransform.getRotateInstance(dx, dy);
trans.invert();
trans.translate(-center.getX(), -center.getY());
Point2D p1a = trans.transform(p1, null);
Point2D p2a = trans.transform(p2, null);
double y = p1a.getY();
double minX = Math.min(p1a.getX(), p2a.getX());
double maxX = Math.max(p1a.getX(), p2a.getX());
if (y == radius || y == -radius) {
if (!isSegment || (0 <= maxX && 0 >= minX)) {
p1a.setLocation(0, y);
trans.inverseTransform(p1a, p1a);
result.add(p1a);
}
} else if (y < radius && y > -radius) {
double x = Math.sqrt(radius * radius - y * y);
if (!isSegment || (-x <= maxX && -x >= minX)) {
p1a.setLocation(-x, y);
trans.inverseTransform(p1a, p1a);
result.add(p1a);
}
if (!isSegment || (x <= maxX && x >= minX)) {
p2a.setLocation(x, y);
trans.inverseTransform(p2a, p2a);
result.add(p2a);
}
}
return result;
}
public static String toString(Point2D point) {
return String.format("(%g, %g)", point.getX(), point.getY());
}
public static String toString(List<Point2D> points) {
StringBuilder str = new StringBuilder("[");
for (int i = 0, n = points.size(); i < n; ++i) {
if (i > 0)
str.append(", ");
str.append(toString(points.get(i)));
}
str.append("]");
return str.toString();
}
}</lang>
{{out}}
<pre>
The intersection points (if any) between:
A circle, center (3, -5) with radius 3, and:
a line containing the points (-10, 11) and (10, -9) is/are:
[(3.00000, -2.00000), (6.00000, -5.00000)]
a segment starting at (-10, 11) and ending at (-11, 12) is/are
[]
a horizontal line containing the points (3, -2) and (7, -2) is/are:
[(3.00000, -2.00000)]
A circle, center (0, 0) with radius 4, and:
a vertical line containing the points (0, -3) and (0, 6) is/are:
[(0.00000, -4.00000), (0.00000, 4.00000)]
a vertical segment starting at (0, -3) and ending at (0, 6) is/are:
[(0.00000, 4.00000)]
A circle, center (4, 2) with radius 5, and:
a line containing the points (6, 3) and (10, 7) is/are:
[(1.00000, -2.00000), (8.00000, 5.00000)]
a segment starting at (7, 4) and ending at (11, 8) is/are:
[(8.00000, 5.00000)]
</pre>
=={{header|Julia}}==
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