Use bullet built-in function

src/items/item.cpp

@@ -43,7 +43,7 @@ Item::Item(ItemType type, const Vec3& xyz, const Vec3& normal,
     m_distance_2        = 1.2f;
     initItem(type, xyz);
 
-    m_original_rotation = Track::createRotationFromNormal(normal);
+    m_original_rotation = shortestArcQuat(Vec3(0, 1, 0), normal);
     m_rotation_angle    = 0.0f;
     m_original_mesh     = mesh;
     m_original_lowmesh  = lowres_mesh;

src/modes/three_strikes_battle.cpp

@@ -711,7 +711,7 @@ void ThreeStrikesBattle::loadCustomModels()
                 const ArenaNode* n = ag->getNode(node);
                 btTransform t;
                 t.setOrigin(n->getCenter());
-                t.setRotation(Track::createRotationFromNormal(n->getNormal()));
+                t.setRotation(shortestArcQuat(Vec3(0, 1, 0), n->getNormal()));
                 pos.push_back(t);
                 pos_created++;
                 used.push_back(node);

src/tracks/track.cpp

@@ -692,7 +692,7 @@ btQuaternion Track::getArenaStartRotation(const Vec3& xyz, float heading)
     }
 
     const Vec3& normal = Graph::get()->getQuad(node)->getNormal();
-    btQuaternion q = createRotationFromNormal(normal);
+    btQuaternion q = shortestArcQuat(Vec3(0, 1, 0), normal);
     btMatrix3x3 m;
     m.setRotation(q);
     return btQuaternion(m.getColumn(1), heading * DEGREE_TO_RAD) * q;

src/tracks/track.hpp

@@ -392,14 +392,6 @@ class Track
 
     static const float NOHIT;
 
-    static btQuaternion createRotationFromNormal(const Vec3& normal)
-    {
-        Vec3 axis = -normal.cross(Vec3(0, 1, 0));
-        if (axis.length() == 0)
-            axis = Vec3(0, 0, 1);
-        return btQuaternion(axis, normal.angle(Vec3(0, 1, 0)));
-    }   // createRotationFromNormal
-
                        Track             (const std::string &filename);
                       ~Track             ();
     void               cleanup           ();