Fix: Orientation now correct if dot product < 0.

source/RobotAPI/components/ArViz/Client/Elements.h

@@ -46,12 +46,20 @@ namespace armarx::viz
             dir = dir.normalized();
             Eigen::Vector3f naturalDir = Eigen::Vector3f::UnitY();
             Eigen::Vector3f cross = naturalDir.cross(dir);
-            float angle = std::acos(naturalDir.dot(dir));
+            float dot = naturalDir.dot(dir);
+            float angle = std::acos(dot);
             if (cross.squaredNorm() < 1.0e-12)
             {
                 // Directions are almost colinear ==> Do no rotation
                 cross = Eigen::Vector3f::UnitX();
-                angle = 0.0f;
+                if (dot < 0)
+                {
+                    angle = M_PI;
+                }
+                else
+                {
+                    angle = 0.0f;
+                }
             }
             Eigen::Vector3f axis = cross.normalized();
             Eigen::Quaternionf ori(Eigen::AngleAxisf(angle, axis));