Added options to apply an impulse for a certain amount of time. This

way pushing two karts away from each other is less abrupt. This is
now enabled, feedback (or tweaks) welcome.


git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@10439 178a84e3-b1eb-0310-8ba1-8eac791a3b58

data/stk_config.xml

@@ -280,6 +280,9 @@
     <!-- collision
          impulse: an additional impulse to be applied in a non-frontal
            collision to push two karts away from each other.
+         impulse-time: The impulse will be applied over a certain time
+           period, which results in less abrupt changes. If set to 0,
+           the impulse is only applied once.
          resitution: restitution value to be used for the kart rigid bodies.
          side-impulse: an additional (artificial) impulse that
            pushes the slower kart out of the way of the faster karts (i.e. 
@@ -289,7 +292,8 @@
            the orientation - if a kart is pushed in the direction it is 
            driving, it will be more (no friction from tires), while when 
            pushed to the side, hardly anything happens.  -->
-    <collision impulse="1500" restitution="0.5" side-impulse="4500"/>
+    <collision impulse="300" impulse-time="0.2" side-impulse="900"
+               restitution="0.5"/>
 
     <!-- Kart-specific plunger and rubber band handling: max-length is
          the maximum length of rubber band before it snaps. force is

src/karts/kart_properties.cpp

@@ -74,6 +74,7 @@ KartProperties::KartProperties(const std::string &filename)
         m_max_speed_reverse_ratio = 
         m_rescue_vert_offset = m_upright_tolerance = 
         m_collision_side_impulse = m_collision_impulse = m_restitution =
+        m_collision_impulse_time = 
         m_upright_max_force = m_suspension_travel_cm =
         m_track_connection_accel =
         m_rubber_band_max_length = m_rubber_band_force =
@@ -428,6 +429,7 @@ void KartProperties::getAllData(const XMLNode * root)
     if(const XMLNode *collision_node = root->getNode("collision"))
     {
         collision_node->get("impulse",       &m_collision_impulse     );
+        collision_node->get("impulse-time",  &m_collision_impulse_time);
         collision_node->get("side-impulse",  &m_collision_side_impulse);
         collision_node->get("restitution",   &m_restitution           );
     }
@@ -595,6 +597,7 @@ void KartProperties::checkAllSet(const std::string &filename)
     CHECK_NEG(m_suspension_travel_cm,       "suspension travel-cm"          );
     CHECK_NEG(m_max_suspension_force,       "suspension max-force"          );
     CHECK_NEG(m_collision_impulse,          "collision impulse"             );
+    CHECK_NEG(m_collision_impulse_time,     "collision impulse-time"        );
     CHECK_NEG(m_restitution,                "collision restitution"         );
     CHECK_NEG(m_collision_side_impulse,     "collision side-impulse"        );
     CHECK_NEG(m_upright_tolerance,          "upright tolerance"             );

src/karts/kart_properties.hpp

@@ -257,6 +257,9 @@ private:
      *  side-side collision away from each other. */
     float m_collision_impulse;
 
+    /** How long the collision impulse should be applied. */
+    float m_collision_impulse_time;
+
     /** The restitution factor to be used in collsions for this kart. */
     float m_restitution;
 
@@ -511,6 +514,9 @@ public:
      *  to another kart in case of a non-frontal collision. */
     float getCollisionImpulse       () const {return m_collision_impulse;}
 
+    /** Returns how long the collision impulse should be applied. */
+    float getCollisionImpulseTime() const { return m_collision_impulse_time;}
+
     /** Returns the restitution factor for this kart. */
     float getRestitution            () const { return m_restitution; }
 

src/physics/btKart.cpp

@@ -117,6 +117,8 @@ void btKart::reset()
     m_is_skidding               = false;
     m_allow_sliding             = false;
     m_num_wheels_on_ground      = 0;
+    m_additional_impulse        = btVector3(0,0,0);
+    m_time_additional_impulse   = 0;
 }   // reset
 
 // ----------------------------------------------------------------------------
@@ -414,6 +416,12 @@ void btKart::updateVehicle( btScalar step )
                                 * btVector3(0, f, 0);
 
     m_chassisBody->applyCentralImpulse(downwards_impulse);
+
+    if(m_time_additional_impulse>0)
+    {
+        m_time_additional_impulse -= step;
+        m_chassisBody->applyCentralImpulse(m_additional_impulse);
+    }
 }   // updateVehicle
 
 // ----------------------------------------------------------------------------

src/physics/btKart.hpp

@@ -92,6 +92,13 @@ private:
      */
     bool                m_allow_sliding;
     
+    /** An additional impulse that is applied for a certain amount of time. */
+    btVector3           m_additional_impulse;
+
+    /** The time the additional impulse should be applied. */
+    float               m_time_additional_impulse;
+
+
     btRigidBody        *m_chassisBody;
 
     int                 m_num_wheels_on_ground;
@@ -199,6 +206,20 @@ public:
     // ------------------------------------------------------------------------
     /** Returns the number of wheels on the ground. */
     unsigned int getNumWheelsOnGround() const {return m_num_wheels_on_ground;}
+    // ------------------------------------------------------------------------
+    /** Sets an impulse that is applied for a certain amount of time.
+     *  \param t Time for the impulse to be active.
+     *  \param imp The impulse to apply.  */
+    void setTimedImpulse(float t, const btVector3 &imp)
+    {
+        // Only add impulse if no other impulse is active.
+        if(m_time_additional_impulse>0) return;
+        m_additional_impulse      = imp;
+        m_time_additional_impulse = t;
+    }   // setTimedImpulse
+    // ------------------------------------------------------------------------
+    /** Returns the time an additional impulse is activated. */
+    float getImpulseTime() const { return m_time_additional_impulse; }
 };   // class btKart
 
-#endif //BT_RAYCASTVEHICLE_H
+#endif //BT_KART_HPP

src/physics/physics.cpp

@@ -351,7 +351,12 @@ void Physics::KartKartCollision(Kart *kart_a, const Vec3 &contact_point_a,
             impulse = Vec3(-dir.getZ(), 0,  dir.getX());
         impulse.normalize();
         impulse *= faster_kart->getKartProperties()->getCollisionImpulse();
-        slower_kart->getBody()->applyCentralImpulse(impulse);
+        float t = 
+            faster_kart->getKartProperties()->getCollisionImpulseTime();
+        if(t>0)
+            slower_kart->getVehicle()->setTimedImpulse(t, impulse);
+        else
+            slower_kart->getBody()->applyCentralImpulse(impulse);
         slower_kart->getBody()->setAngularVelocity(btVector3(0,0,0));
         // Apply some impulse to the slower kart as well?
     }
@@ -367,7 +372,12 @@ void Physics::KartKartCollision(Kart *kart_a, const Vec3 &contact_point_a,
             impulse = Vec3( dir.getZ(), 0, -dir.getX());
         impulse.normalize();
         impulse *= slower_kart->getKartProperties()->getCollisionImpulse();
-        faster_kart->getBody()->applyCentralImpulse(impulse);
+        float t = 
+            faster_kart->getKartProperties()->getCollisionImpulseTime();
+        if(t>0)
+            faster_kart->getVehicle()->setTimedImpulse(t, impulse);
+        else
+            faster_kart->getBody()->applyCentralImpulse(impulse);
         faster_kart->getBody()->setAngularVelocity(btVector3(0,0,0));
 
         // Then the slower kart
@@ -379,7 +389,11 @@ void Physics::KartKartCollision(Kart *kart_a, const Vec3 &contact_point_a,
 
         impulse.normalize();
         impulse *= faster_kart->getKartProperties()->getCollisionImpulse();
-        slower_kart->getBody()->applyCentralImpulse(impulse);
+        t = faster_kart->getKartProperties()->getCollisionImpulseTime();
+        if(t>0)
+            slower_kart->getVehicle()->setTimedImpulse(t, impulse);
+        else
+            slower_kart->getBody()->applyCentralImpulse(impulse);
         slower_kart->getBody()->setAngularVelocity(btVector3(0,0,0));
     }