From 87cc77ae4c8828b1a23a200955f2ca9a4855ef39 Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Sun, 6 Dec 2009 10:52:50 +0000
Subject: [PATCH] Tweak train control algorithm

---
 include/IController.hpp        |   1 +
 maps/goods_demo/goods_demo.bin | Bin 4364 -> 4364 bytes
 maps/goods_demo/goods_demo.xml |   4 ++++
 src/Engine.cpp                 |  40 +++++++++++++++++++++++++++------
 src/Game.cpp                   |   3 +++
 5 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/include/IController.hpp b/include/IController.hpp
index d51604d..334103b 100644
--- a/include/IController.hpp
+++ b/include/IController.hpp
@@ -27,6 +27,7 @@ enum Action {
    SHOVEL_COAL,
    THROTTLE_UP,
    THROTTLE_DOWN,
+   TOGGLE_REVERSE,
    GO_STRAIGHT_ON,
    GO_LEFT,
    GO_RIGHT,
diff --git a/maps/goods_demo/goods_demo.bin b/maps/goods_demo/goods_demo.bin
index 502d61b2b70d1797f6ed0ee967f594eb5aa7d61e..7a6792e669603adb3168593635e2fc7c8f31f198 100644
GIT binary patch
delta 289
zcmeBC>QUP8g^gp@Oi4Qsp4`ALGg*Q?f#cj6A6pOx3e@nxI1CI7_LDELiA-L=!7*8d
z!$QWy*w}v7%$asT1$Jl8oB<j!)9(D4Gqyms?c@rMjLA0K9Ks-7Kn3<7#Slf3lYet$
zN}C#Qwx2!oCQ$B-JrlzLAbTcQO-5SU<a*9b`HZw>_Ni%V4uAjKJItIZ=>Sp#G6Q5D
z5Kq?Um7J`=<s%7FXJ~8;R+pZ}=D^6%0Cv>*$rstwCnxZ7P2R?3B>=JoWYYit@(v&!
ilQ*!)OkTjP0Cb{-AjoQv6)^4RCU4}m+Pt6JmlXh56mACq

delta 296
zcmeBC>QUP8g>CWyX7<Uy`FSRHvkOj^U{9F%frW*Efx&)q1AEQn21XW+b7y?)!2%c9
zL?$ob;Fzq!VIcz(JbUJh-K?3CU<I>g&a^vw#>Z}Q1xJQ-M%ps_b7y+&Gt$!RXV07o
zW`i^V@#NnenbPOaoUu<&V{>3+U~n)q{%jB8gVY1@<a*9bc_xMf_J9A|J4~G!>0oGV
z3|0e@H!(H_SvFapS8}ofmyaY!A4tvb|M3q0|I0g=8gI4-Iq2NvjlBAk6<Am%@8Gf!
z0okH!T<nmX=H@VG=1s6ElP|ETOmq;QY|U*c0@4MtW#&vt2asz)UYTfUzIi{lFDn2P
CCU6k|

diff --git a/maps/goods_demo/goods_demo.xml b/maps/goods_demo/goods_demo.xml
index 06c4083..9623bf7 100644
--- a/maps/goods_demo/goods_demo.xml
+++ b/maps/goods_demo/goods_demo.xml
@@ -319,6 +319,10 @@
 <curvedTrack startAngle="270" finishAngle="360" radius="3"/>
 </tile>
 
+<tile x="13" y="14">
+<straightTrack align="x"/>
+</tile>
+
 <tile x="13" y="20">
 <curvedTrack startAngle="180" finishAngle="270" radius="3"/>
 </tile>
diff --git a/src/Engine.cpp b/src/Engine.cpp
index 65488d4..57da0f9 100644
--- a/src/Engine.cpp
+++ b/src/Engine.cpp
@@ -91,6 +91,8 @@ private:
    double statTractiveEffort;
    bool isBrakeOn;
    int myThrottle;     // Ratio measured in tenths
+   bool reverse;
+   bool haveStopped;
 
    track::Choice nextChoice;
 
@@ -103,12 +105,15 @@ private:
    static const double TRACTIVE_EFFORT_KNEE;
 
    static const double INIT_PRESSURE, INIT_TEMP;
+
+   static const double STOP_SPEED;
 };
 
 const float Engine::MODEL_SCALE(0.4f);
 const double Engine::TRACTIVE_EFFORT_KNEE(10.0);
 const double Engine::INIT_PRESSURE(0.2);
 const double Engine::INIT_TEMP(50.0);
+const double Engine::STOP_SPEED(0.01);
 
 Engine::Engine(IResourcePtr aRes)
    : mySpeed(0.0), myMass(29.0),
@@ -116,6 +121,8 @@ Engine::Engine(IResourcePtr aRes)
      myFireTemp(INIT_TEMP),
      statTractiveEffort(34.7),
      isBrakeOn(true), myThrottle(0),
+     reverse(false),
+     haveStopped(true),
      resource(aRes)
 {
    static IXMLParserPtr parser = makeXMLParser("schemas/engine.xsd");
@@ -148,9 +155,9 @@ double Engine::tractiveEffort() const
 // Calculate the magnitude of the resistance on the train
 double Engine::resistance() const
 {
-   const double a = 4.0;
-   const double b = 0.05;
-   const double c = 0.006;
+   const double a = 0.0;
+   const double b = 0.09;
+   const double c = 0.02;
    return a + b*mySpeed + c*mySpeed*mySpeed;
 }
 
@@ -159,7 +166,17 @@ double Engine::brakeForce() const
 {
    const double beta = 0.09;
    const double g = 9.78;
-   return myMass * g * beta;
+
+   // Brake always acts against direction of motion
+   double dir;
+   if (abs(mySpeed) < STOP_SPEED)
+      dir = 0.0;
+   else if (mySpeed < 0.0)
+      dir = -1.0;
+   else
+      dir = 1.0;
+   
+   return myMass * g * beta * dir;
 }
 
 // Compute the next state of the engine
@@ -180,12 +197,18 @@ void Engine::update(int aDelta)
    const double deltaSeconds = aDelta / 1000.0f;
    const double a = ((netP - Q - B) / myMass) * deltaSeconds;
 
-   mySpeed = max(mySpeed + a, 0.0);
+   //   mySpeed = max(mySpeed + a, 0.0);
+   mySpeed += a;
+
+   if (abs(mySpeed) < STOP_SPEED) {
+      mySpeed = 0.0;
+      haveStopped = true;
+   }
    
-   /*debug() << "P=" << netP << ", Q=" << Q
+   debug() << "P=" << netP << ", Q=" << Q
            << ", B=" << B
            << ", a=" << a << ", v=" << mySpeed
-           << " (delta=" << aDelta << ")";*/
+           << " (delta=" << aDelta << ")";
 }
 
 track::Choice Engine::consumeChoice()
@@ -211,6 +234,9 @@ void Engine::actOn(Action anAction)
    case THROTTLE_DOWN:
       myThrottle = max(myThrottle - 1, 0);
       break;
+   case TOGGLE_REVERSE:
+      reverse = !reverse;
+      break;
    case GO_STRAIGHT_ON:
       nextChoice = track::CHOOSE_STRAIGHT_ON;
       break;
diff --git a/src/Game.cpp b/src/Game.cpp
index b4acbc2..c55afad 100644
--- a/src/Game.cpp
+++ b/src/Game.cpp
@@ -264,6 +264,9 @@ void Game::onKeyDown(SDLKey aKey)
    case SDLK_b:
       train->controller()->actOn(BRAKE_TOGGLE);
       break;
+   case SDLK_r:
+      train->controller()->actOn(TOGGLE_REVERSE);
+      break;
    case SDLK_LCTRL:
       train->controller()->actOn(SHOVEL_COAL);
       break;
-- 
2.39.2