updated tcr

1 files changed, 33 insertions, 0 deletions

diff --git a/geometry/circle.cpp b/geometry/circle.cpp
new file mode 100644
index 0000000..f49ea27
--- /dev/null
+++ b/geometry/circle.cpp
@@ -0,0 +1,33 @@
+// berechnet die Schnittpunkte von zwei kreisen
+// (Kreise dürfen nicht gleich sein!)
+vector<pt> circleIntersection(pt c1, double r1, 
+															pt c2, double r2) {
+	double d = abs(c1 - c2);
+	if (d < abs(r1 - r2) || d > abs(r1 + r2)) return {};
+	double a = (r1 * r1 - r2 * r2 + d * d) / (2 * d);
+	pt p = (c2 - c1) * a / d + c1;
+	if (d == abs(r1 - r2) || d == abs(r1 + r2)) return {p};
+	double h = sqrt(r1 * r1 - a * a);
+	return {p + pt{0, 1} * (c2 - c1) * h / d,
+					p - pt{0, 1} * (c2 - c1) * h / d};
+}
+
+// berechnet die Schnittpunkte zwischen
+// einem Kreis(Kugel) und einer Grade 2d und 3d
+vector<pt> circleRayIntersection(pt center, double r, 
+																 pt orig, pt dir) {
+	vector<pt> result;
+	double a = dot(dir, dir);
+	double b = 2 * dot(dir, orig - center);
+	double c = dot(orig - center, orig - center) - r * r;
+	double discr = b * b - 4 * a * c;
+	if (discr >= 0) {
+		//t in [0, 1] => schnitt mit segment [orig, orig + dir]
+		double t1 = -(b + sqrt(discr)) / (2 * a);
+		double t2 = -(b - sqrt(discr)) / (2 * a);
+		if (t1 >= 0) result.push_back(t1 * dir + orig);
+		if (t2 >= 0 && abs(t1 - t2) > EPS) {
+			result.push_back(t2 * dir + orig);
+	}}
+	return result;
+}