From b04194303a8b24cf5e1f77153ad9ddabcb24e22e Mon Sep 17 00:00:00 2001
From: hikerstk <hikerstk@178a84e3-b1eb-0310-8ba1-8eac791a3b58>
Date: Wed, 17 Oct 2012 06:14:43 +0000
Subject: [PATCH] AIs will now reduce their speed if they are too far ahead of
 the player.

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@11697 178a84e3-b1eb-0310-8ba1-8eac791a3b58
---
 data/stk_config.xml                    |  7 +++-
 src/karts/controller/ai_properties.cpp | 26 +++++++-------
 src/karts/controller/ai_properties.hpp | 12 ++++++-
 src/karts/controller/skidding_ai.cpp   | 49 ++++++++++++++------------
 src/karts/controller/skidding_ai.hpp   |  4 +++
 5 files changed, 62 insertions(+), 36 deletions(-)

diff --git a/data/stk_config.xml b/data/stk_config.xml
index 2895b3d64..7554563c9 100644
--- a/data/stk_config.xml
+++ b/data/stk_config.xml
@@ -249,12 +249,17 @@
            distance ahead, the value for the largest distance is used,
            and similarly if the kart is more than the minimum value
            behind).
+         speed-cap: Fraction of maximum speed the kart should drive
+           at. Used to slow down karts that are ahead of the player.
+           Note that setting this to a value >1 does NOT increase
+           the speed the kart can drive at!
     -->
     <ai max-item-angle="0.7" max-item-angle-high-speed="0.3"
         time-full-steer="0.1"
         bad-item-closeness="6"
         straight-length-for-zipper="35"
-        rb-skid-probability="-50:1.0 -20:0.7 20:0.2 50:0.0"/>
+        rb-skid-probability="-50:1.0 -20:0.7 20:0.2 50:0.0"
+        speed-cap="10:1.0 50:0.8"/>
 
     <!-- Slipstream: length: How far behind a kart slipstream works
          collect-time: How many seconds of sstream give  maximum benefit
diff --git a/src/karts/controller/ai_properties.cpp b/src/karts/controller/ai_properties.cpp
index dee25e698..417a18e7d 100644
--- a/src/karts/controller/ai_properties.cpp
+++ b/src/karts/controller/ai_properties.cpp
@@ -27,6 +27,7 @@ float AIProperties::UNDEFINED = -99.9f;
  */
 AIProperties::AIProperties()
             : m_skid_probability(/*decreasing*/false)
+            , m_speed_cap(/*decreasing*/true)
 {
     m_max_item_angle             = UNDEFINED;
     m_max_item_angle_high_speed  = UNDEFINED;
@@ -47,13 +48,8 @@ void AIProperties::load(const XMLNode *ai_node)
     ai_node->get("bad-item-closeness",        &m_bad_item_closeness_2      );
     ai_node->get("straight-length-for-zipper",&m_straight_length_for_zipper);
     ai_node->get("rb-skid-probability",       &m_skid_probability          );
+    ai_node->get("speed-cap",                 &m_speed_cap                 );
 
-    if(m_skid_probability.size()==0)
-    {
-        printf("No skid probability defined.\n");
-        exit(-1);
-    }
- 
     // We actually need the square of the distance later
     m_bad_item_closeness_2 *= m_bad_item_closeness_2;
     
@@ -76,12 +72,18 @@ void AIProperties::checkAllSet(const std::string &filename) const
     CHECK_NEG(m_bad_item_closeness_2,      "bad-item-closeness"        );
     CHECK_NEG(m_straight_length_for_zipper,"straight-length-for-zipper");
 
+    if(m_skid_probability.size()==0)
+    {
+        printf("No skid probability defined.\n");
+        exit(-1);
+    }
+ 
+    if(m_speed_cap.size()==0)
+    {
+        printf("No speed cap defined.\n");
+        exit(-1);
+    }
+
 }   // checkAllSet
 
-// ----------------------------------------------------------------------------
-void AIProperties::copyFrom(const AIProperties *destination)
-{
-    *this = *destination;
-}   // copyFrom
-
 /* EOF */
diff --git a/src/karts/controller/ai_properties.hpp b/src/karts/controller/ai_properties.hpp
index 1bd3f3ad5..a843121e4 100644
--- a/src/karts/controller/ai_properties.hpp
+++ b/src/karts/controller/ai_properties.hpp
@@ -72,11 +72,14 @@ protected:
 
     /** The array of (distance, skid_probability) points. */
     InterpolationArray m_skid_probability;
+
+    /** To cap maximum speed if the kart is ahead of the player. */
+    InterpolationArray m_speed_cap;
+
 public:
 
          AIProperties();
     void load(const XMLNode *skid_node);
-    void copyFrom(const AIProperties *destination);
     void checkAllSet(const std::string &filename) const;
     // ------------------------------------------------------------------------
     /** Returns the skidding probability dependent on the specified distance
@@ -85,6 +88,13 @@ public:
     {
         return m_skid_probability.get(distance);
     }   // getSkiddingProbability
+    // ------------------------------------------------------------------------
+    /** Returns the fraction of maximum speed the AI should drive at, depending
+     *  on the distance from the player. */
+    float getSpeedCap(float distance) const
+    {
+        return m_speed_cap.get(distance);
+    }   // getSpeedCap
 };   // AIProperties
 
 
diff --git a/src/karts/controller/skidding_ai.cpp b/src/karts/controller/skidding_ai.cpp
index afa0870df..ee48356be 100644
--- a/src/karts/controller/skidding_ai.cpp
+++ b/src/karts/controller/skidding_ai.cpp
@@ -358,6 +358,9 @@ void SkiddingAI::update(float dt)
     // Get information that is needed by more than 1 of the handling funcs
     computeNearestKarts();
 
+    m_kart->setSlowdown(MaxSpeed::MS_DECREASE_AI, 
+                        m_ai_properties->getSpeedCap(m_distance_to_player),
+                        /*fade_in_time*/0.0f);
     //Detect if we are going to crash with the track and/or kart
     checkCrashes(m_kart->getXYZ());
     determineTrackDirection();
@@ -1359,22 +1362,37 @@ void SkiddingAI::computeNearestKarts()
     }
 
     m_distance_ahead = m_distance_behind = 9999999.9f;
-    float my_dist = m_world->getDistanceDownTrackForKart(m_kart->getWorldKartId());
+    float my_dist = m_world->getOverallDistance(m_kart->getWorldKartId());
     if(m_kart_ahead)
     {
         m_distance_ahead = 
-            m_world->getDistanceDownTrackForKart(m_kart_ahead->getWorldKartId())
-          - my_dist;
-        if(m_distance_ahead<0.0f)
-            m_distance_ahead += m_track->getTrackLength();
+            m_world->getOverallDistance(m_kart_ahead->getWorldKartId())
+            -my_dist;
     }
     if(m_kart_behind)
     {
         m_distance_behind = my_dist
-            -m_world->getDistanceDownTrackForKart(m_kart_behind->getWorldKartId());
-        if(m_distance_behind<0.0f)
-            m_distance_behind += m_track->getTrackLength();
+            -m_world->getOverallDistance(m_kart_behind->getWorldKartId());
     }
+
+    // Compute distance to nearest player kart
+    m_distance_to_player = 0.0f;
+    unsigned int n = ProfileWorld::isProfileMode() 
+                   ? 0 : race_manager->getNumPlayers();
+    // Initially use m_distance_to_player as 'maximum overall distance'
+    for(unsigned int i=0; i<n; i++)
+    {
+        unsigned int kart_id = 
+            m_world->getPlayerKart(i)->getWorldKartId();
+        if(m_world->getOverallDistance(kart_id)>m_distance_to_player)
+            m_distance_to_player = m_world->getOverallDistance(kart_id);
+    }
+    if(m_distance_to_player==0.0f)
+        m_distance_to_player = 999999.9f;   // force best driving 
+    // Now convert 'maximum overall distance' to distance to player.
+    m_distance_to_player = 
+                m_world->getOverallDistance(m_kart->getWorldKartId())
+                - m_distance_to_player;
 }   // computeNearestKarts
 
 //-----------------------------------------------------------------------------
@@ -2223,22 +2241,9 @@ void SkiddingAI::setSteering(float angle, float dt)
                                     : KartControl::SC_LEFT; 
         if(!m_tried_skid_last_frame)
         {
-            float max_distance = 0.0f;
-            unsigned int n = ProfileWorld::isProfileMode() 
-                         ? 0 : race_manager->getNumPlayers();
-
-            for(unsigned int i=0; i<n; i++)
-            {
-                unsigned int kart_id = 
-                    m_world->getPlayerKart(i)->getWorldKartId();
-                if(m_world->getOverallDistance(kart_id)>max_distance)
-                    max_distance = m_world->getOverallDistance(kart_id);
-            }
-            if(max_distance==0.0f)
-                max_distance = 999999.9f;   // force best driving 
             float distance = 
                 m_world->getOverallDistance(m_kart->getWorldKartId())
-                     - max_distance;
+                - m_distance_to_player;
             int prob = (int)
                     (100.0f*m_ai_properties->getSkiddingProbability(distance));
 
diff --git a/src/karts/controller/skidding_ai.hpp b/src/karts/controller/skidding_ai.hpp
index ae9391350..d90f34d17 100644
--- a/src/karts/controller/skidding_ai.hpp
+++ b/src/karts/controller/skidding_ai.hpp
@@ -1,3 +1,4 @@
+
 //
 //  SuperTuxKart - a fun racing game with go-kart
 //  Copyright (C) 2004-2005 Steve Baker <sjbaker1@airmail.net>
@@ -151,6 +152,9 @@ private:
      *  (which would make it more difficult to avoid items). */
     bool m_avoid_item_close;
 
+    /** Distance to the player, used for rubber-banding. */
+    float m_distance_to_player;
+
     /** A random number generator to decide if the AI should skid or not. */
     RandomGenerator m_random_skid;