separate zipper velocity change from suspension/turning impulses

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/branches/irrlicht@3874 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/karts/kart.cpp

@@ -681,18 +681,13 @@ void Kart::handleZipper()
     // Ignore a zipper that's activated while braking
     if(m_controls.m_brake) return;
     m_zipper_time_left  = stk_config->m_zipper_time;
+
     btVector3 v         = m_body->getLinearVelocity();
     float current_speed = v.length();
     float speed         = std::min(current_speed+stk_config->m_zipper_speed_gain,
                                    getMaxSpeedOnTerrain());
-    // If the speed is too low, very minor components of the velocity vector
+
-    // can become too big. E.g. each kart has a z component (to offset gravity
+    m_vehicle->activateZipper(speed);
-    // I assume, around 0.16) --> if the karts are (nearly) at standstill,
-    // the z component is exaggerated, resulting in a jump. Even if Z
-    // is set to 0, minor left/right movements are then too strong.
-    // Therefore a zipper only adds the speed if the speed is at least 1
-    // (experimentally found valud).  It also avoids NAN problems (if v=0).
-    if(current_speed>1.0f) m_body->setLinearVelocity(v*(speed/current_speed));
 }   // handleZipper
 
 //-----------------------------------------------------------------------------
@@ -1067,6 +1062,8 @@ void Kart::endRescue()
     m_body->setLinearVelocity (btVector3(0.0f,0.0f,0.0f));
     m_body->setAngularVelocity(btVector3(0.0f,0.0f,0.0f));
 
+    m_vehicle->deactivateZipper();
+
     // let the mode decide where to put the kart
     RaceManager::getWorld()->moveKartAfterRescue(this, m_body);
 

src/physics/btKart.cpp

@@ -32,6 +32,9 @@ btKart::btKart(const btVehicleTuning& tuning,btRigidBody* chassis,
 : btRaycastVehicle(tuning, chassis, raycaster)
 {
     m_track_connect_accel = track_connect_accel;
+
+    m_zipper_active = false;
+    m_zipper_velocity = btScalar(0);
 }
 
 // ----------------------------------------------------------------------------
@@ -414,42 +417,47 @@ void	btKart::updateFriction(btScalar	timeStep)
 
             btScalar	rollingFriction = 0.f;
 
-            if (groundObject)
-            {
-                if (wheelInfo.m_engineForce != 0.f)
-                {
-                    rollingFriction = wheelInfo.m_engineForce* timeStep;
-                } else
-                {
-                    btScalar defaultRollingFrictionImpulse = 0.f;
-                    btScalar maxImpulse = wheelInfo.m_brake ? wheelInfo.m_brake : defaultRollingFrictionImpulse;
-                    btWheelContactPoint contactPt(m_chassisBody,groundObject,wheelInfo.m_raycastInfo.m_contactPointWS,m_forwardWS[wheel],maxImpulse);
-                    rollingFriction = calcRollingFriction(contactPt);
-                    // This is a work around for the problem that a kart shakes
-                    // if it is braking: we get a minor impulse forward, which
-                    // bullet then tries to offset by applying a backward
-                    // impulse - which is a bit too big, causing a impulse
-                    // backwards, ... till the kart is shaking backwards and
-                    // forwards
-                    if(wheelInfo.m_brake && fabsf(rollingFriction)<10)
-                        rollingFriction=0;
-                }
-            }
-
-            //switch between active rolling (throttle), braking and non-active rolling friction (no throttle/break)
-
-
-
-
             m_forwardImpulse[wheel] = btScalar(0.);
             m_wheelInfo[wheel].m_skidInfo= btScalar(1.);
 
             if (groundObject)
             {
-                m_forwardImpulse[wheel] = rollingFriction;//wheelInfo.m_engineForce* timeStep;
+                if (m_zipper_active)
-            }
+                {
+                    if (wheel==2 || wheel==3)
+                    {
+                        m_forwardImpulse[wheel] = 0.5*(m_zipper_velocity - getRigidBody()->getLinearVelocity().length()) / m_chassisBody->getInvMass();
+                    }
+                }
+                else
+                {
 
+                    if (wheelInfo.m_engineForce != 0.f)
+                    {
+                        rollingFriction = wheelInfo.m_engineForce* timeStep;
+                    } else
+                    {
+                        //switch between active rolling (throttle), braking and non-active rolling friction (no throttle/break)
+                        btScalar defaultRollingFrictionImpulse = 0.f;
+                        btScalar maxImpulse = wheelInfo.m_brake ? wheelInfo.m_brake : defaultRollingFrictionImpulse;
+                        btWheelContactPoint contactPt(m_chassisBody,groundObject,wheelInfo.m_raycastInfo.m_contactPointWS,m_forwardWS[wheel],maxImpulse);
+                        rollingFriction = calcRollingFriction(contactPt);
+                        // This is a work around for the problem that a kart shakes
+                        // if it is braking: we get a minor impulse forward, which
+                        // bullet then tries to offset by applying a backward
+                        // impulse - which is a bit too big, causing a impulse
+                        // backwards, ... till the kart is shaking backwards and
+                        // forwards
+                        if(wheelInfo.m_brake && fabsf(rollingFriction)<10)
+                            rollingFriction=0;
+                    }
+
+                    m_forwardImpulse[wheel] = rollingFriction;//wheelInfo.m_engineForce* timeStep;
+                }
+            }
         }
+
+        m_zipper_active = false;
     }
 
 

src/physics/btKart.hpp

@@ -24,6 +24,8 @@ class btKart : public btRaycastVehicle
     void         defaultInit(const btVehicleTuning& tuning);
     btScalar     m_track_connect_accel;
     btScalar     m_skidding_factor;
+    bool         m_zipper_active;
+    btScalar     m_zipper_velocity;
 public:
     btKart(const btVehicleTuning& tuning,btRigidBody* chassis,
            btVehicleRaycaster* raycaster, float track_connect_accel );
@@ -36,6 +38,8 @@ public:
                                      const btVector3& hitPoint,
                                      const btVector3& hitNormal,btScalar depth);
     void         setPitchControl(btScalar pitch) { m_pitchControl = pitch; }
+    void         activateZipper(btScalar vel) { m_zipper_active = true; m_zipper_velocity = vel; }
+    void         deactivateZipper() { m_zipper_active = false; }
     void         updateSuspension(btScalar deltaTime);
     virtual void updateFriction(btScalar timeStep);
 };