Make the physics settings configurable, but default to use the old

settings for now.

data/stk_config.xml

@@ -415,11 +415,14 @@
          physical-wheel-position: Defines where the 'physical' (raycast)
            wheel will be located. It's a weight factor with 0 = being
            at the widest side of the bevel, 1 = at the front and
-           narrowest part of the kart.  -->
+           narrowest part of the kart. If the value is less than 0, the old
+           physics settings are used which places the raycast wheels
+           outside of the chassis and results in more stable physical
+           behaviour of the karts. -->
     <collision impulse-type="normal" 
                impulse="3000" impulse-time="0.1" terrain-impulse="8000"
                restitution="1.0" bevel-factor="0.5 0.0 0.7"
-               physical-wheel-position="0.5" />
+               physical-wheel-position="-1" />
 			 
      <!-- If a kart starts within the specified time after 'go',
           it receives the corresponding bonus from 'boost'. Those

src/karts/kart.cpp

@@ -606,7 +606,10 @@ void Kart::createPhysics()
                 if (y == -1)
                 {
                     int index = (x + 1) / 2 + 1 - z;  // get index of wheel
-                    if(true)
+                    float f = getKartProperties()->getPhysicalWheelPosition();
+                    // f < 0 indicates to use the old physics position, i.e. 
+                    // to place the wheels outside of the chassis
+                    if(f<0)
                     {
                         const Vec3 cs = getKartProperties()->getGravityCenterShift();
                         wheel_pos[index].setX(x*0.5f*getKartWidth()+cs.getX());
@@ -621,7 +624,6 @@ void Kart::createPhysics()
                     }
                     else
                     {
-                        float f = getKartProperties()->getPhysicalWheelPosition();
                         wheel_pos[index] = p*(orig_factor*(1.0f - f) + bevel_factor*f);
                         wheel_pos[index].setY(0);
                     }

src/karts/kart_properties.cpp

@@ -272,8 +272,15 @@ void KartProperties::load(const std::string &filename, const std::string &node)
         m_gravity_center_shift.setZ(0);
     }
 
-    //FIXME: magix 0.25 factor to keep it compatible with previous tourning
+    if(m_physical_wheel_position < 0)
-    m_wheel_base = fabsf( m_kart_model->getLength() - (true ? 0 : -0.25f));
+        m_wheel_base = fabsf(m_kart_model->getLength() );
+    else
+    {
+        // The new (atm unused) physical position results in steering to be
+        // not sharp enough - therefore decrease the wheel base somewhat to
+        // approximate the behaviour of the old steering.
+        m_wheel_base = fabsf(m_kart_model->getLength() - 0.25f);
+    }
 
     // Now convert the turn radius into turn angle:
     for(unsigned int i=0; i<m_turn_angle_at_speed.size(); i++)

src/karts/kart_properties.hpp

@@ -152,7 +152,11 @@ private:
 
     /** The position of the physical wheel is a weighted average of the
      *  two ends of the beveled shape. This determines the weight: 0 = 
-     *  a the widest end, 1 = at the narrowest front end. */
+     *  a the widest end, 1 = at the narrowest front end. If the value is 
+     *  < 0, the old physics settings are used which places the raycast
+     *  wheels outside of the chassis - but result in a more stable
+     *  physics behaviour (which is therefore atm still the default).
+     */
     float m_physical_wheel_position;
 
     /** Time a kart is moved upwards after when it is rescued. */
@@ -916,7 +920,9 @@ public:
     // ------------------------------------------------------------------------
     /** Returns position of the physical wheel is a weighted average of the
      *  two ends of the beveled shape. This determines the weight: 0 = 
-     *  a the widest end, 1 = at the narrowest, front end. */
+     *  a the widest end, 1 = at the narrowest, front end. If the value is <0,
+     *  the old physics position is picked, which placed the raycast wheels
+     *  outside of the chassis, but gives more stable physics. */
     const float getPhysicalWheelPosition() const 
     {
         return m_physical_wheel_position;