1 files changed, 35 insertions, 0 deletions
diff --git a/src/gldisc.cpp b/src/gldisc.cpp
index ee0a06b..85dd6d4 100644
--- a/src/gldisc.cpp
+++ b/src/gldisc.cpp
@@ -107,6 +107,41 @@ bool GLDisc::isHit(QVector3D p1, QVector3D p2)
         return true;
     }
 
+    // Check if the mouse line is hitting the outer disc side
+    QVector2D vecXYProjection = lineVector.toVector2D();
+    QVector2D vecXYStart = p1.toVector2D();
+
+    // Solved via the "Mitternachtsformel"
+    float a = QVector2D::dotProduct(vecXYProjection, vecXYProjection);
+    float b = 2 * QVector2D::dotProduct(vecXYStart, vecXYProjection);
+    float c = QVector2D::dotProduct(vecXYStart,
+                                    vecXYStart) - m_circleRadius * m_circleRadius;
+
+    float discriminant = b * b - 4 * a * c;
+
+    if (discriminant >= 0)
+    {
+        discriminant = sqrt(discriminant);
+
+        float lambda1 = (-b - discriminant) / (2*a);
+
+        float z1 = (p1 + lambda1 * lineVector).z();
+
+        if(z1 >= 0 && z1 <= m_height)
+        {
+            return true;
+        }
+
+        float lambda2 = (-b + discriminant) / (2*a);
+
+        float z2 = (p1 + lambda2 * lineVector).z();
+
+        if(z2 >= 0 && z2 <= m_height)
+        {
+            return true;
+        }
+    }
+
     return false;
 }