Adjust wheel position in case of leaning: move the wheels on the side

that is higher in the air a bit further down so that they touch the ground.
Fixed #2400.

src/karts/ghost_kart.cpp

@@ -114,7 +114,8 @@ void GhostKart::update(float dt)
     Moveable::updateGraphics(dt, center_shift, btQuaternion(0, 0, 0, 1));
     Moveable::updatePosition();
     getKartModel()->update(dt, dt*(m_all_physic_info[idx].m_speed),
-        m_all_physic_info[idx].m_steer, m_all_physic_info[idx].m_speed, idx);
+        m_all_physic_info[idx].m_steer, m_all_physic_info[idx].m_speed,
+        /*lean*/0.0f, idx);
 
     getKartGFX()->setGFXFromReplay(m_all_replay_events[idx].m_nitro_usage,
         m_all_replay_events[idx].m_zipper_usage,

src/karts/kart.cpp

@@ -2745,12 +2745,12 @@ void Kart::updateGraphics(float dt, const Vec3& offset_xyz,
 
     // If the kart is leaning, part of the kart might end up 'in' the track.
     // To avoid this, raise the kart enough to offset the leaning.
-    float lean_height = tan(fabsf(m_current_lean)) * getKartWidth()*0.5f;
+    float lean_height = tan(m_current_lean) * getKartWidth()*0.5f;
 
     Vec3 center_shift(0, 0, 0);
 
     center_shift.setY(m_skidding->getGraphicalJumpOffset()
-                      + lean_height
+                      + fabsf(lean_height)
                       +m_graphical_y_offset);
     center_shift = getTrans().getBasis() * center_shift;
 
@@ -2760,7 +2760,7 @@ void Kart::updateGraphics(float dt, const Vec3& offset_xyz,
 
     // m_speed*dt is the distance the kart has moved, which determines
     // how much the wheels need to rotate.
-    m_kart_model->update(dt, m_speed*dt, getSteerPercent(), m_speed);
+    m_kart_model->update(dt, m_speed*dt, getSteerPercent(), m_speed, lean_height);
 
     // Determine the shadow position from the terrain Y position. This
     // leaves the shadow on the ground even if the kart is jumping because

src/karts/kart_model.cpp

@@ -689,7 +689,7 @@ void KartModel::reset()
             m_wheel_node[i]->setRotation(rotation);
         }
     }
-    update(0.0f, 0.0f, 0.0f, 0.0f);
+    update(0.0f, 0.0f, 0.0f, 0.0f, 0.0f);
 
     // Stop any animations currently being played.
     setAnimation(KartModel::AF_DEFAULT);
@@ -833,10 +833,12 @@ void KartModel::setDefaultSuspension()
  *  \param suspension Suspension height for all four wheels.
  *  \param speed The speed of the kart in meters/sec, used for the
  *         speed-weighted objects' animations
+ *  \param current_lean_angle How much the kart is leaning (positive meaning
+ *         left side down)
  *  \param gt_replay_index The index to get replay data, used by ghost kart
  */
 void KartModel::update(float dt, float distance, float steer, float speed,
-                       int gt_replay_index)
+                       float current_lean_angle, int gt_replay_index)
 {
     core::vector3df wheel_steer(0, steer*30.0f, 0);
 
@@ -866,13 +868,27 @@ void KartModel::update(float dt, float distance, float steer, float speed,
         else
         {
             suspension_length = m_kart->getVehicle()->getWheelInfo(i).
-                m_raycastInfo.m_suspensionLength;
+                                m_raycastInfo.m_suspensionLength;
         }
 
         // Check documentation of Kart::updateGraphics for the following line
         pos.Y +=   m_default_physics_suspension[i]
                  - suspension_length
                  - m_kart_lowest_point;
+
+        // Adjust the wheel position for lean: the lean can cause the 'leaned
+        // to' side to be partly in the ground - which looks ok (like the tyres
+        // being compressed), but the other side will be in the air. To avoid
+        // this, increase the position of the wheels on the side that are
+        // higher in the ground so that the wheel still touch the ground.
+        if(current_lean_angle > 0 && (i&1) == 0)   // i&1 == 0: left side
+        {
+            pos.Y -= current_lean_angle;
+        }
+        else if (current_lean_angle < 0 && (i&1) == 1)   // i&1 == 1: right side
+        {
+            pos.Y += current_lean_angle;
+        }
         m_wheel_node[i]->setPosition(pos);
 
         // Now calculate the new rotation: (old + change) mod 360

src/karts/kart_model.hpp

@@ -238,6 +238,7 @@ public:
     bool          loadModels(const KartProperties &kart_properties);
     void          setDefaultSuspension();
     void          update(float dt, float distance, float steer, float speed,
+                         float current_lean_angle,
                          int gt_replay_index = -1);
     void          finishedRace();
     scene::ISceneNode*

src/states_screens/feature_unlocked.cpp

@@ -300,7 +300,7 @@ void FeatureUnlockedCutScene::init()
             m_unlocked_stuff[n].m_root_gift_node = kart_model->attachModel(true, false);
             m_unlocked_stuff[n].m_scale = 5.0f;
             kart_model->setAnimation(KartModel::AF_DEFAULT);
-            kart_model->update(0.0f, 0.0f, 0.0f, 0.0f); // set model current frame to "center"
+            kart_model->update(0.0f, 0.0f, 0.0f, 0.0f, 0.0f); // set model current frame to "center"
 
 #ifdef DEBUG
             m_unlocked_stuff[n].m_root_gift_node->setName("unlocked kart");