Added support to modify the angular factor of a kart. The angular

factor can be used to reduce the effect of an impulse for roll
and pitch - keeping karts more parallel to the ground.

data/kart_characteristics.xml

@@ -45,6 +45,9 @@
                 the ground if its off ground. Reduces the affect if a kart loses
                 contact with the ground (i.e. it then can't steer or accelerate
                 anymore).
+	    angular-factor: Factor to change angular impulses. X and Z rotations
+                are damped to avoid that karts in a collision are too easily pushed
+	        into a roll or pitch, which makes them topple over
             smooth-flying-impulse: apply a torque impulse to flying kart to keep
                 them parallel to the ground. -->
         <stability roll-influence="0.3"
@@ -52,6 +55,7 @@
                    chassis-angular-damping="0"
                    downward-impulse-factor="5"
                    track-connection-accel="2"
+		   angular-factor="1.0 1.0 1.0"
                    smooth-flying-impulse="250" />
 
         <!-- Turning

src/karts/abstract_characteristic.cpp

@@ -74,6 +74,8 @@ AbstractCharacteristic::ValueType AbstractCharacteristic::getType(
         return TYPE_FLOAT;
     case STABILITY_TRACK_CONNECTION_ACCEL:
         return TYPE_FLOAT;
+    case STABILITY_ANGULAR_FACTOR:
+        return TYPE_FLOAT_VECTOR;
     case STABILITY_SMOOTH_FLYING_IMPULSE:
         return TYPE_FLOAT;
     case TURN_RADIUS:
@@ -304,6 +306,8 @@ std::string AbstractCharacteristic::getName(CharacteristicType type)
         return "STABILITY_DOWNWARD_IMPULSE_FACTOR";
     case STABILITY_TRACK_CONNECTION_ACCEL:
         return "STABILITY_TRACK_CONNECTION_ACCEL";
+    case STABILITY_ANGULAR_FACTOR:
+        return "STABILITY_ANGULAR_FACTOR";
     case STABILITY_SMOOTH_FLYING_IMPULSE:
         return "STABILITY_SMOOTH_FLYING_IMPULSE";
     case TURN_RADIUS:
@@ -626,6 +630,18 @@ float AbstractCharacteristic::getStabilityTrackConnectionAccel() const
     return result;
 }  // getStabilityTrackConnectionAccel
 
+// ----------------------------------------------------------------------------
+std::vector<float> AbstractCharacteristic::getStabilityAngularFactor() const
+{
+    std::vector<float> result;
+    bool is_set = false;
+    process(STABILITY_ANGULAR_FACTOR, &result, &is_set);
+    if (!is_set)
+        Log::fatal("AbstractCharacteristic", "Can't get characteristic %s",
+                    getName(STABILITY_ANGULAR_FACTOR).c_str());
+    return result;
+}  // getStabilityAngularFactor
+
 // ----------------------------------------------------------------------------
 float AbstractCharacteristic::getStabilitySmoothFlyingImpulse() const
 {
@@ -1006,7 +1022,7 @@ float AbstractCharacteristic::getFrictionKartFriction() const
     process(FRICTION_KART_FRICTION, &result, &is_set);
     if (!is_set)
         Log::fatal("AbstractCharacteristic", "Can't get characteristic %s",
-            getName(FRICTION_KART_FRICTION).c_str());
+                    getName(FRICTION_KART_FRICTION).c_str());
     return result;
 }  // getFrictionKartFriction
 

src/karts/abstract_characteristic.hpp

@@ -84,6 +84,7 @@ public:
         STABILITY_CHASSIS_ANGULAR_DAMPING,
         STABILITY_DOWNWARD_IMPULSE_FACTOR,
         STABILITY_TRACK_CONNECTION_ACCEL,
+        STABILITY_ANGULAR_FACTOR,
         STABILITY_SMOOTH_FLYING_IMPULSE,
 
         // Turn
@@ -269,6 +270,7 @@ public:
     float getStabilityChassisAngularDamping() const;
     float getStabilityDownwardImpulseFactor() const;
     float getStabilityTrackConnectionAccel() const;
+    std::vector<float> getStabilityAngularFactor() const;
     float getStabilitySmoothFlyingImpulse() const;
 
     InterpolationArray getTurnRadius() const;

src/karts/kart.cpp

@@ -668,6 +668,10 @@ void Kart::createPhysics()
     trans.setIdentity();
     createBody(mass, trans, &m_kart_chassis,
                m_kart_properties->getRestitution());
+    std::vector<float> ang_fact = m_kart_properties->getStabilityAngularFactor();
+    // The angular factor (with X and Z values <1) helps to keep the kart
+    // upright, especially in case of a collision.
+    m_body->setAngularFactor(Vec3(ang_fact[0], ang_fact[1], ang_fact[2]));
     m_body->setFriction(m_kart_properties->getFrictionKartFriction());
     m_user_pointer.set(this);
     m_body->setDamping(m_kart_properties->getStabilityChassisLinearDamping(),

src/karts/kart_properties.cpp

@@ -597,6 +597,12 @@ float KartProperties::getStabilityTrackConnectionAccel() const
     return m_cached_characteristic->getStabilityTrackConnectionAccel();
 }  // getStabilityTrackConnectionAccel
 
+// ----------------------------------------------------------------------------
+std::vector<float> KartProperties::getStabilityAngularFactor() const
+{
+    return m_cached_characteristic->getStabilityAngularFactor();
+}  // getStabilityAngularFactor
+
 // ----------------------------------------------------------------------------
 float KartProperties::getStabilitySmoothFlyingImpulse() const
 {

src/karts/kart_properties.hpp

@@ -431,6 +431,7 @@ public:
     float getStabilityChassisAngularDamping() const;
     float getStabilityDownwardImpulseFactor() const;
     float getStabilityTrackConnectionAccel() const;
+    std::vector<float> getStabilityAngularFactor() const;
     float getStabilitySmoothFlyingImpulse() const;
 
     InterpolationArray getTurnRadius() const;

src/karts/xml_characteristic.cpp

@@ -343,6 +343,8 @@ void XmlCharacteristic::load(const XMLNode *node)
             &m_values[STABILITY_DOWNWARD_IMPULSE_FACTOR]);
         sub_node->get("track-connection-accel",
             &m_values[STABILITY_TRACK_CONNECTION_ACCEL]);
+        sub_node->get("angular-factor",
+            &m_values[STABILITY_ANGULAR_FACTOR]);
         sub_node->get("smooth-flying-impulse",
             &m_values[STABILITY_SMOOTH_FLYING_IMPULSE]);
     }

tools/create_kart_properties.py

@@ -28,7 +28,7 @@ import sys
 # Each line contains a topic and the attributes of that topic.
 # This model is used for the xml file and to access the kart properties in the code.
 characteristics = """Suspension: stiffness, rest, travel, expSpringResponse(bool), maxForce
-Stability: rollInfluence, chassisLinearDamping, chassisAngularDamping, downwardImpulseFactor, trackConnectionAccel, smoothFlyingImpulse
+Stability: rollInfluence, chassisLinearDamping, chassisAngularDamping, downwardImpulseFactor, trackConnectionAccel, angularFactor(std::vector<float>/floatVector), smoothFlyingImpulse
 Turn: radius(InterpolationArray), timeResetSteer, timeFullSteer(InterpolationArray)
 Engine: power, maxSpeed, brakeFactor, brakeTimeIncrease, maxSpeedReverseRatio
 Gear: switchRatio(std::vector<float>/floatVector), powerIncrease(std::vector<float>/floatVector)