Smooth skidding rotation when entering a cannon.

src/karts/cannon_animation.cpp

@@ -27,9 +27,22 @@
 
 #include "LinearMath/btTransform.h"
 
+/** The constructor for the cannon animation. 
+ *  \param kart The kart to be animated.
+ *  \param ipo The IPO (blender interpolation curve) which the kart
+ *         should follow.
+ *  \param start_left, start_right: Left and right end points of the line
+ *         that the kart just crossed.
+ *  \param end_left, end_right: Left and right end points of the line at
+ *         which the kart finishes.
+ *  \param skid_rot Visual rotation of the kart due to skidding (while this
+ *         value can be queried, the AbstractkartAnimation constructor
+ *         resets the value to 0, so it needs to be passed in.
+ */
 CannonAnimation::CannonAnimation(AbstractKart *kart, Ipo *ipo,
                                  const Vec3 &start_left, const Vec3 &start_right,
-                                 const Vec3 &end_left,   const Vec3 &end_right   )
+                                 const Vec3 &end_left,   const Vec3 &end_right,
+                                 float skid_rot)
                : AbstractKartAnimation(kart, "CannonAnimation")
 {
     m_curve  = new AnimationBase(ipo);
@@ -126,10 +139,10 @@ CannonAnimation::CannonAnimation(AbstractKart *kart, Ipo *ipo,
     m_curve->getDerivativeAt(0, &tangent);
     // Get the current kart orientation
     Vec3 forward = m_kart->getTrans().getBasis().getColumn(2);
-    forward.normalize();
     Vec3 v1(tangent), v2(forward);
     v1.setY(0); v2.setY(0);
-    m_delta_heading = shortestArcQuatNormalize2(v1, v2);
+    m_delta_heading = shortestArcQuatNormalize2(v1, v2) 
+                    * btQuaternion(Vec3(0,1,0), skid_rot);
 
 
     // The previous call to m_curve->update will set the internal timer
@@ -171,7 +184,6 @@ void CannonAnimation::update(float dt)
                              &tangent);
     // Get the current kart orientation
     Vec3 forward = m_kart->getTrans().getBasis().getColumn(2);
-    forward.normalize();
     
     // Heading
     // -------

src/karts/cannon_animation.hpp

@@ -64,7 +64,8 @@ protected:
 public:
              CannonAnimation(AbstractKart *kart, Ipo *ipo,
                              const Vec3 &start_left, const Vec3 &start_right,
-                             const Vec3 &end_left, const Vec3 &end_right);
+                             const Vec3 &end_left, const Vec3 &end_right,
+                             float skid_rot);
     virtual ~CannonAnimation();
     virtual void  update(float dt);
 

src/tracks/check_cannon.cpp

@@ -27,6 +27,7 @@
 #include "io/xml_node.hpp"
 #include "karts/abstract_kart.hpp"
 #include "karts/cannon_animation.hpp"
+#include "karts/skidding.hpp"
 #include "modes/world.hpp"
 
 
@@ -142,6 +143,10 @@ void CheckCannon::trigger(unsigned int kart_index)
     AbstractKart *kart = World::getWorld()->getKart(kart_index);
     if(kart->getKartAnimation()) return;
 
+    // The constructor AbstractKartAnimation resets the skidding to 0. So in
+    // order to smooth rotate the kart, we need to keep the current visual
+    // rotation and pass it to the CannonAnimation.
+    float skid_rot = kart->getSkidding()->getVisualSkidRotation();
     new CannonAnimation(kart, m_curve->clone(), getLeftPoint(), getRightPoint(),
-                        m_target_left, m_target_right);
+                        m_target_left, m_target_right, skid_rot);
 }   // CheckCannon