1 files changed, 60 insertions, 5 deletions

diff --git a/src/gldisc.cpp b/src/gldisc.cpp
index a2c22b5..85dd6d4 100644
--- a/src/gldisc.cpp
+++ b/src/gldisc.cpp
@@ -29,10 +29,10 @@ void GLDisc::makeSurface(QVector<GLPoint> *pointContainer,
 
         m_points->append(GLPoint(m_circleRadius * tmp, -v_Z, tmpTextCoo, m_color));
         m_points->append(GLPoint(m_circleRadius * tmp, tmp, tmpTextCoo, m_color));
-        m_points->append(GLPoint(QVector3D(m_circleRadius * tmp, m_height), tmp, tmpTextCoo,
-                                 m_color));
-        m_points->append(GLPoint(QVector3D(m_circleRadius * tmp, m_height), v_Z, tmpTextCoo,
-                                 m_color));
+        m_points->append(GLPoint(QVector3D(m_circleRadius * tmp, m_height), tmp,
+                                 tmpTextCoo, m_color));
+        m_points->append(GLPoint(QVector3D(m_circleRadius * tmp, m_height), v_Z,
+                                 tmpTextCoo, m_color));
     }
 
     m_points->append(GLPoint(m_height * v_Z, v_Z, QVector3D(0.5, 0.5, 0.0),
@@ -82,12 +82,67 @@ void GLDisc::makeSurface(QVector<GLPoint> *pointContainer,
 
 bool GLDisc::isHit(QVector3D p1, QVector3D p2)
 {
-    if(!GLBody::isHit(p1, p2))
+    if (!GLBody::isHit(p1, p2))
     {
         return false;
     }
 
+    QVector3D lineVector = p2 - p1;
 
+    // Calculate intersection point with the xy plane
+    QVector3D vecBottom = p1 + lineVector * (-p1.z() / lineVector.z());
+
+    if (vecBottom.length() < m_circleRadius)
+    {
+        return true;
+    }
+
+    // Calculate intersection point with the xy + m_heigth plane
+    // Then drop z so that we get a projection onto the xy plane
+    QVector3D vecTop = (p1 + lineVector * ((m_height - p1.z()) /
+                                           lineVector.z())).toVector2D();
+
+    if (vecTop.length() < m_circleRadius)
+    {
+        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;
 }
 
 QVector2D GLDisc::calculatePoint(double sideAngle)