Made the physics time step size configurable in the config file.

data/stk_config.xml

@@ -92,6 +92,7 @@
           case (all three normals discarded, the interpolation will just
           return the normal of the triangle (i.e. de facto no interpolation),
           but it helps making smoothing much more useful without fixing tracks.
+      fps: The physics timestep size
       default-track-friction: Default friction to be used for the track and
           any track/library pbject.
       default-moveable-friction: Default friction to be used for any moveable,
@@ -99,6 +100,7 @@
       -->
   <physics smooth-normals="true"
            smooth-angle-limit="0.65"
+           fps="120"
            default-track-friction="0.5"
            default-moveable-friction="0.5" />
 

src/config/stk_config.cpp

@@ -139,6 +139,7 @@ void STKConfig::load(const std::string &filename)
     CHECK_NEG(m_replay_dt,                 "replay delta-t"             );
     CHECK_NEG(m_smooth_angle_limit,        "physics smooth-angle-limit" );
     CHECK_NEG(m_default_track_friction,    "physics default-track-friction");
+    CHECK_NEG(m_physics_fps,               "physics fps"                );
     CHECK_NEG(m_default_moveable_friction, "physics default-moveable-friction");
 
     // Square distance to make distance checks cheaper (no sqrt)
@@ -160,6 +161,7 @@ void STKConfig::init_defaults()
         m_smooth_angle_limit     = m_penalty_time              =
         m_default_track_friction = m_default_moveable_friction =
         UNDEFINED;
+    m_physics_fps                = -100;
     m_bubblegum_counter          = -100;
     m_shield_restrict_weapos     = false;
     m_max_karts                  = -100;
@@ -249,6 +251,7 @@ void STKConfig::getAllData(const XMLNode * root)
         physics_node->get("default-track-friction", &m_default_track_friction);
         physics_node->get("default-moveable-friction",
                                                  &m_default_moveable_friction);
+        physics_node->get("fps",                    &m_physics_fps           );
     }
 
     if (const XMLNode *startup_node= root->getNode("startup"))

src/config/stk_config.hpp

@@ -93,6 +93,9 @@ public:
     /** Default friction to be used for any moveable, e.g. karts, balls. */
     float m_default_moveable_friction;
 
+    /** Default FPS rate for physics. */
+    int m_physics_fps;
+
     int   m_max_skidmarks;           /**<Maximum number of skid marks/kart.  */
     float m_skid_fadeout_time;       /**<Time till skidmarks fade away.      */
     float m_near_ground;             /**<Determines when a kart is not near

src/physics/physics.cpp

@@ -152,7 +152,8 @@ void Physics::update(float dt)
 
     // Maximum of three substeps. This will work for framerate down to
     // 20 FPS (bullet default frequency is 60 HZ).
-    m_dynamics_world->stepSimulation(dt, 6, 1.0f/120.0f);
+    m_dynamics_world->stepSimulation(dt, max_num_steps,
+                                     1.0f / stk_config->m_physics_fps);
 
     // Now handle the actual collision. Note: flyables can not be removed
     // inside of this loop, since the same flyables might hit more than one