From 266dc02a44c5666860b108e3c97f35f4f360f6a6 Mon Sep 17 00:00:00 2001
From: hiker <henrichsjoerg@gmail.com>
Date: Tue, 13 Nov 2018 18:34:49 +1100
Subject: [PATCH] Removed support for cushioning falls, instead increase max
 suspensiom force and damping compression to allow karts to fall without
 colliding with the terrain. Needs an increase in network protocol version.

---
 data/kart_characteristics.xml |   4 +-
 data/stk_config.xml           |   2 +-
 src/karts/kart_rewinder.cpp   |   2 -
 src/network/server_config.cpp |  12 ----
 src/network/server_config.hpp |   2 +-
 src/physics/btKart.cpp        | 103 ++--------------------------------
 src/physics/btKart.hpp        |  16 ------
 7 files changed, 10 insertions(+), 131 deletions(-)
 mode change 100644 => 100755 src/network/server_config.cpp

diff --git a/data/kart_characteristics.xml b/data/kart_characteristics.xml
index 767bc2bcd..3407aa5ee 100644
--- a/data/kart_characteristics.xml
+++ b/data/kart_characteristics.xml
@@ -35,7 +35,7 @@
                 for details.
             max-force: Maximum suspension force -->
         <suspension stiffness="280" rest="0.3" travel="0.29"
-            exp-spring-response="false" max-force="12000" />
+            exp-spring-response="false" max-force="32000" />
 
         <!-- Values related to stability of the chassis: damping, and reduced
                 impact of roll.
@@ -117,7 +117,7 @@
                 position of the physics raycast wheels relative to the center of
                 gravity. Default is to use the corners of the chassis to attach
                 the wheels to. -->
-        <wheels damping-relaxation="35"  damping-compression="5">
+        <wheels damping-relaxation="35"  damping-compression="15">
             <front-right position="0.38 0 0.6"   />
             <front-left  position="-0.38 0 0.6"  />
             <rear-right  position="0.38 0 -0.6"  />
diff --git a/data/stk_config.xml b/data/stk_config.xml
index 0c75d6b9d..ab20b8481 100644
--- a/data/stk_config.xml
+++ b/data/stk_config.xml
@@ -11,7 +11,7 @@
 
   <!-- Minimum and maxium server versions that be be read by this binary.
        Older versions will be ignored. -->
-  <server-version min="3" max="3"/>
+  <server-version min="4" max="4"/>
 
   <!-- Maximum number of karts to be used at the same time. This limit
        can easily be increased, but some tracks might not have valid start
diff --git a/src/karts/kart_rewinder.cpp b/src/karts/kart_rewinder.cpp
index e83c21d66..38e72eac9 100644
--- a/src/karts/kart_rewinder.cpp
+++ b/src/karts/kart_rewinder.cpp
@@ -156,7 +156,6 @@ BareNetworkString* KartRewinder::saveState(std::vector<std::string>* ru)
     buffer->add(body->getAngularVelocity());
     buffer->addFloat(m_vehicle->getTimedRotationTime());
     buffer->add(m_vehicle->getTimedRotation());
-    buffer->addUInt8(m_vehicle->getCushioningDisableTime());
 
     // For collision rewind
     buffer->addUInt16(m_bounce_back_ticks);
@@ -265,7 +264,6 @@ void KartRewinder::restoreState(BareNetworkString *buffer, int count)
     float time_rot = buffer->getFloat();
     // Set timed rotation divides by time_rot
     m_vehicle->setTimedRotation(time_rot, time_rot*buffer->getVec3());
-    m_vehicle->setCushioningDisableTime(buffer->getUInt8());
 
     // Collision rewind
     m_bounce_back_ticks = buffer->getUInt16();
diff --git a/src/network/server_config.cpp b/src/network/server_config.cpp
old mode 100644
new mode 100755
index 5d5c5d539..5d33002d0
--- a/src/network/server_config.cpp
+++ b/src/network/server_config.cpp
@@ -136,18 +136,6 @@ void loadServerConfigXML(const XMLNode* root)
         return;
     }
 
-    /*int config_file_version = -1;
-    if (root->get("version", &config_file_version) < 1 ||
-        config_file_version < stk_config->m_min_server_version ||
-        config_file_version > stk_config->m_max_server_version)
-    {
-        Log::info("ServerConfig", "Your config file was not compatible, "
-            "so it was deleted and a new one will be created.");
-        delete root;
-        writeServerConfigToDisk();
-        return;
-    }*/
-
     for (unsigned i = 0; i < g_server_params.size(); i++)
         g_server_params[i]->findYourDataInAChildOf(root);
 
diff --git a/src/network/server_config.hpp b/src/network/server_config.hpp
index c700f39b7..15eff8fc7 100644
--- a/src/network/server_config.hpp
+++ b/src/network/server_config.hpp
@@ -276,7 +276,7 @@ namespace ServerConfig
 
     // ========================================================================
     /** Server version, will be advanced if there are protocol changes. */
-    static const uint32_t m_server_version = 3;
+    static const uint32_t m_server_version = 4;
     // ========================================================================
     void loadServerConfig(const std::string& path = "");
     // ------------------------------------------------------------------------
diff --git a/src/physics/btKart.cpp b/src/physics/btKart.cpp
index a5a6a32cd..071e75c61 100644
--- a/src/physics/btKart.cpp
+++ b/src/physics/btKart.cpp
@@ -26,10 +26,6 @@
 #include "karts/kart.hpp"
 #include "karts/kart_model.hpp"
 #include "karts/kart_properties.hpp"
-#undef DEBUG_CUSHIONING
-#ifdef DEBUG_CUSHIONING
-#include "modes/world.hpp"
-#endif
 #include "physics/triangle_mesh.hpp"
 #include "tracks/terrain_info.hpp"
 #include "tracks/track.hpp"
@@ -129,7 +125,6 @@ void btKart::reset()
     m_time_additional_rotation   = 0;
     m_max_speed                  = -1.0f;
     m_min_speed                  = 0.0f;
-    m_cushioning_disable_time    = 0;
 
     // Set the brakes so that karts don't slide downhill
     setAllBrakes(5.0f);
@@ -449,9 +444,8 @@ void btKart::updateVehicle( btScalar step )
     if(m_num_wheels_on_ground==0)
     {
         btVector3 kart_up    = getChassisWorldTransform().getBasis().getColumn(1);
-        btVector3 terrain_up =
-            m_kart->getMaterial() && m_kart->getMaterial()->hasGravity() ?
-            m_kart->getNormal() : Vec3(0, 1, 0);
+        btVector3 terrain_up = -m_chassisBody->getGravity();
+        terrain_up = terrain_up.normalize();
         // Length of axis depends on the angle - i.e. the further awat
         // the kart is from being upright, the larger the applied impulse
         // will be, resulting in fast changes when the kart is on its
@@ -467,7 +461,9 @@ void btKart::updateVehicle( btScalar step )
         av.setZ(0);
         m_chassisBody->setAngularVelocity(av);
         // Give a nicely balanced feeling for rebalancing the kart
-        m_chassisBody->applyTorqueImpulse(axis * m_kart->getKartProperties()->getStabilitySmoothFlyingImpulse());
+        float smoothing = m_kart->getKartProperties()
+                                ->getStabilitySmoothFlyingImpulse();
+        m_chassisBody->applyTorqueImpulse(axis * smoothing);
     }
 
     // Apply suspension forcen (i.e. upwards force)
@@ -494,93 +490,6 @@ void btKart::updateVehicle( btScalar step )
 
     }
 
-
-    // Test if the kart is falling so fast 
-    // that the chassis might hit the track
-    // ------------------------------------
-    int wheel_index = 0;
-    float min_susp = m_wheelInfo[0].m_raycastInfo.m_suspensionLength;
-    for (int i = 1; i<m_wheelInfo.size(); i++)
-    {
-        btWheelInfo &wheel = m_wheelInfo[i];
-        if (wheel.m_raycastInfo.m_suspensionLength < min_susp)
-        {
-            min_susp = wheel.m_raycastInfo.m_suspensionLength;
-            wheel_index = i;
-        }
-    }
-
-    // Cushioning test: if the kart is falling fast, the suspension might
-    // not be strong enough to prevent the chassis from hitting the ground.
-    // Try to detect this upcoming crash, and apply an upward impulse if
-    // necessary that will slow down the falling speed.
-    if(m_cushioning_disable_time>0) m_cushioning_disable_time --;
-
-    bool needed_cushioning = false;
-    btVector3 v =
-        m_chassisBody->getVelocityInLocalPoint(m_wheelInfo[wheel_index]
-                                               .m_chassisConnectionPointCS);
-    btVector3 down = -m_chassisBody->getGravity();
-    down.normalize();
-    btVector3 v_down = (v * down) * down;
-    btScalar offset=0.1f;
-
-#ifdef DEBUG_CUSHIONING
-    Log::verbose("physics",
-        "World %d wheel %d  lsuspl %f vdown %f overall speed %f lenght %f",
-        World::getWorld()->getTimeTicks(),
-        wheel_index,
-        m_wheelInfo[wheel_index].m_raycastInfo.m_suspensionLength,
-        -v_down.getY(),
-        -v_down.getY() + 9.8*step,
-        step * (-v_down.getY() + 9.8*step)+offset);
-#endif
-    // If the kart is falling, estimate the distance the kart will fall
-    // in the next time step: the speed gets increased by the gravity*dt.
-    // This approximation is still not good enough (either because of
-    // kart rotation that can be changed, or perhaps because of the
-    // collision threshold used by bullet) - i.e. it would sometimes not
-    // predict the upcoming collision correcty - so we add an offset
-    // to the predicted kart movement, which was found experimentally:
-    btScalar gravity = m_chassisBody->getGravity().length();
-    if (v_down.getY()<0 && m_cushioning_disable_time==0 &&
-        m_wheelInfo[wheel_index].m_raycastInfo.m_suspensionLength 
-                            < step * (-v_down.getY()+gravity*step)+offset)
-    {
-        // Disable more cushioning for 1 second. This avoids the problem
-        // of hovering: a kart gets cushioned on a down-sloping area, still
-        // moves forwards, gets cushioned again etc. --> kart is hovering
-        // and not controllable. 
-        m_cushioning_disable_time = 120;
-
-        needed_cushioning = true;
-        btVector3 impulse = down * (-v_down.getY() + gravity*step)
-                          / m_chassisBody->getInvMass();
-#ifdef DEBUG_CUSHIONING
-        float v_old = m_chassisBody->getLinearVelocity().getY();
-#endif
-        m_chassisBody->applyCentralImpulse(impulse);
-#ifdef DEBUG_CUSHIONING
-        Log::verbose("physics",
-            "World %d Cushioning imp %f vdown %f from %f m/s to %f m/s "
-            "contact %f kart %f susp %f relspeed %f",
-            World::getWorld()->getTimeTicks(),
-            impulse.getY(),
-            -v_down.getY(),
-            v_old,
-            m_chassisBody->getLinearVelocity().getY(),
-            m_wheelInfo[wheel_index].m_raycastInfo.m_isInContact ?
-            m_wheelInfo[wheel_index].m_raycastInfo.m_contactPointWS.getY()
-            : -100,
-            m_chassisBody->getWorldTransform().getOrigin().getY(),
-            m_wheelInfo[wheel_index].m_raycastInfo.m_suspensionLength,
-            m_chassisBody->getVelocityInLocalPoint(m_wheelInfo[wheel_index]
-                                                   .m_chassisConnectionPointCS)
-        );
-#endif
-    }
-
-
     // Update friction (i.e. forward force)
     // ------------------------------------
     updateFriction( step);
@@ -588,7 +497,7 @@ void btKart::updateVehicle( btScalar step )
     // If configured, add a force to keep karts on the track
     // -----------------------------------------------------
     float dif = m_kart->getKartProperties()->getStabilityDownwardImpulseFactor();
-    if(dif!=0 && m_num_wheels_on_ground==4 && !needed_cushioning)
+    if(dif!=0 && m_num_wheels_on_ground==4)
     {
         float f = -fabsf(m_kart->getSpeed()) * dif;
         btVector3 downwards_impulse = m_chassisBody->getWorldTransform().getBasis()
diff --git a/src/physics/btKart.hpp b/src/physics/btKart.hpp
index bfcecffba..01932e26e 100644
--- a/src/physics/btKart.hpp
+++ b/src/physics/btKart.hpp
@@ -93,9 +93,6 @@ private:
     /** Number of wheels that touch the ground. */
     int                 m_num_wheels_on_ground;
 
-    /** Number of time steps during which cushioning is disabled. */
-    unsigned int        m_cushioning_disable_time;
-
     /** Index of the right axis. */
     int                 m_indexRightAxis;
     /** Index of the up axis. */
@@ -252,19 +249,6 @@ public:
     // ------------------------------------------------------------------------
     float getTimedRotationTime() const { return m_time_additional_rotation;  }
     // ------------------------------------------------------------------------
-    /** Returns the time cushioning is disabled. Used for networking state
-     *  saving. */
-    unsigned int getCushioningDisableTime() const
-    {
-        return m_cushioning_disable_time;
-    }  // getCushioningDisableTime
-    // ------------------------------------------------------------------------
-    /** Sets the cushioning disable time. Used for networking state saving. */
-    void setCushioningDisableTime(unsigned int cdt)
-    {
-        m_cushioning_disable_time = cdt;
-    }   // setCushioningDisableTime
-    // ------------------------------------------------------------------------
     /** Sets the maximum speed for this kart. */
     void setMaxSpeed(float new_max_speed) 
     {