Handle max- and min-speed capping in phyiscs (which is frame rate

independent).

src/karts/max_speed.cpp

@@ -133,7 +133,7 @@ void MaxSpeed::instantSpeedIncrease(unsigned int category,
     // the speed might be too low for certain jumps).
     if(speed < m_min_speed) speed = m_min_speed;
 
-    m_kart->getVehicle()->instantSpeedIncreaseTo(speed);
+    m_kart->getVehicle()->setMinSpeed(speed);
 
 }   // instantSpeedIncrease
 
@@ -318,10 +318,15 @@ void MaxSpeed::update(float dt)
     // --------------------------------------
     if(m_min_speed > 0 && m_kart->getSpeed() < m_min_speed)
     {
-        m_kart->getVehicle()->instantSpeedIncreaseTo(m_min_speed);
+        m_kart->getVehicle()->setMinSpeed(m_min_speed);
     }
-    else if ( m_kart->getSpeed()>m_current_max_speed && m_kart->isOnGround() )
-        m_kart->getVehicle()->capSpeed(m_current_max_speed);
+    else 
+        m_kart->getVehicle()->setMinSpeed(0);   // no additional acceleration
+
+    if (m_kart->isOnGround())
+        m_kart->getVehicle()->setMaxSpeed(m_current_max_speed);
+    else
+        m_kart->getVehicle()->setMaxSpeed(9999.9f);
 
 }   // update
 

src/modes/overworld.cpp

@@ -278,7 +278,7 @@ void OverWorld::onMouseClick(int x, int y)
         // be the location of the challenge bubble.
         AbstractKart* kart = getKart(0);
         kart->setXYZ(challenge->m_position);
-        kart->getVehicle()->capSpeed(0);
+        kart->getVehicle()->setMaxSpeed(0);
 
         unsigned int index   = getRescuePositionIndex(kart);
         btTransform s        = getRescueTransform(index);

src/physics/btKart.cpp

@@ -128,6 +128,8 @@ void btKart::reset()
     m_additional_rotation        = btVector3(0,0,0);
     m_time_additional_rotation   = 0;
     m_visual_rotation            = 0;
+    m_max_speed                  = 9999.9f;
+    m_min_speed                  = 0.0f;
 
     // Set the brakes so that karts don't slide downhill
     setAllBrakes(5.0f);
@@ -551,6 +553,7 @@ void btKart::updateVehicle( btScalar step )
         iwt.setRotation(iwt.getRotation()*add_rot);
         m_time_additional_rotation -= dt;
     }
+    adjustSpeed(m_min_speed, m_max_speed);
 }   // updateVehicle
 
 // ----------------------------------------------------------------------------
@@ -1019,7 +1022,7 @@ void btKart::setSliding(bool active)
  *  specified speed.
  *  \param speed The speed to reach.
  */
-void btKart::instantSpeedIncreaseTo(float speed)
+void btKart::instantSpeedIncreaseTo(btScalar speed)
 {
     // Avoid that a speed 'increase' might cause a slowdown
     if (m_chassisBody->getLinearVelocity().length2() > speed*speed)
@@ -1030,18 +1033,35 @@ void btKart::instantSpeedIncreaseTo(float speed)
 }   // activateZipper
 
 // ----------------------------------------------------------------------------
-/** Caps the speed at a given value. If necessary the kart will
- *  instantaneously change its speed. */
-void btKart::capSpeed(float max_speed)
+/** Adjusts the velocity of this kart to be at least the specified minimum,
+ *  and less than or equal to the maximum. If necessary the kart will
+ *  instantaneously change its speed.
+ *  \param min_speed Minimum speed, 0 means no effect.
+ *  \param max_speed Maximum speed the kart is allowed to have.
+ */
+void btKart::adjustSpeed(btScalar min_speed, btScalar max_speed)
 {
     const btVector3 &velocity = m_chassisBody->getLinearVelocity();
     float speed = velocity.length();
-    if(speed!=0)
+    if (speed < min_speed && min_speed > 0)
+    {
+        if (speed == 0)
+        {
+            m_chassisBody->setLinearVelocity(btVector3(0, 0, min_speed));
+        }
+        else
+        {
+
+            const float velocity_ratio = min_speed / speed;
+            m_chassisBody->setLinearVelocity(velocity * velocity_ratio);
+        }
+    }
+    else if (speed >0 && speed>max_speed)
     {
         const float velocity_ratio = max_speed / speed;
         m_chassisBody->setLinearVelocity(velocity * velocity_ratio);
     }
-}   // capSpeed
+}   // adjustSpeed
 
 // ----------------------------------------------------------------------------
 //Shorter version of above raycast function. This is used when projecting

src/physics/btKart.hpp

@@ -124,6 +124,14 @@ private:
      *  for skid marks. */
     float m_visual_rotation;
 
+    /** Minimum speed for the kart. Used e.g. for zippers. Setting this value
+     *  will potentially instantaneously accelerate the kart to the minimum
+     *  speed requested (in the next physics step). */
+    btScalar m_min_speed;
+
+    /** Maximum speed for the kart. */
+    btScalar m_max_speed;
+
     /** True if the visual wheels touch the ground. */
     bool m_visual_wheels_touch_ground;
 
@@ -176,8 +184,8 @@ public:
     virtual void       updateFriction(btScalar timeStep);
 public:
     void               setSliding(bool active);
-    void               instantSpeedIncreaseTo(float speed);
-    void               capSpeed(float max_speed);
+    void               instantSpeedIncreaseTo(btScalar speed);
+    void               adjustSpeed(btScalar min_speed, btScalar max_speed);
     void               updateAllWheelPositions();
     // ------------------------------------------------------------------------
     /** Returns true if both rear visual wheels touch the ground. */
@@ -276,6 +284,12 @@ public:
     /** Returns the current zipper speed. */
     float getInstantSpeedIncrease() const { return m_zipper_speed; }
     // ------------------------------------------------------------------------
+    /** Sets the maximum speed for this kart. */
+    void setMaxSpeed(float s) { m_max_speed = s;  }
+    // ------------------------------------------------------------------------
+    /** Sets the minimum speed for this kart. */
+    void setMinSpeed(float s) { m_min_speed = s; }
+    // ------------------------------------------------------------------------
     void resetInstantSpeed() { m_zipper_speed = 0;  }
 };   // class btKart