From 8cb40714b8ebff98aee8edd08662ce1469378ebc Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Sat, 20 Mar 2010 17:49:31 +0000
Subject: [PATCH] Fix bug in SlopeTrack gradient calculation

---
 src/Engine.cpp     | 15 ++++++++-------
 src/SlopeTrack.cpp |  2 +-
 src/Train.cpp      | 13 +++++--------
 3 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/src/Engine.cpp b/src/Engine.cpp
index 2706333..c34f775 100644
--- a/src/Engine.cpp
+++ b/src/Engine.cpp
@@ -207,13 +207,14 @@ void Engine::update(int delta, float gradient)
    const double B = isBrakeOn ? brakeForce() : 0.0;
    const double G = gravity(gradient);   
 
-#if 1
-   if (gradient > 0.01f)
-      debug() << "U = " << gradient;
-   else if (gradient < -0.01f)
-      debug() << "D =" << gradient;
-   else
-      debug() << "F =" << gradient;
+#if 0
+   static float lastGradient = gradient;
+   if (abs(gradient - lastGradient) > 0.01f) {
+      error() << "too big gradient change "
+              << lastGradient << " -> "
+              << gradient;
+   }
+   lastGradient = gradient;
 #endif
    
    // The applied tractive effort is controlled by the throttle
diff --git a/src/SlopeTrack.cpp b/src/SlopeTrack.cpp
index bee5bfa..78d3473 100644
--- a/src/SlopeTrack.cpp
+++ b/src/SlopeTrack.cpp
@@ -206,7 +206,7 @@ float SlopeTrack::gradient(const track::TravelToken& token, float delta) const
    if (token.direction == -axis)
       delta = length - delta;
 
-   return curve.deriv(delta).y;
+   return curve.deriv(delta / length).y;
 }
 
 void SlopeTrack::transform(const track::TravelToken& token, float delta) const
diff --git a/src/Train.cpp b/src/Train.cpp
index 314b000..9b6d04f 100644
--- a/src/Train.cpp
+++ b/src/Train.cpp
@@ -286,16 +286,11 @@ void Train::update(int delta)
         it != parts.end(); ++it) {
       float gradient = (*it).travelToken.gradient((*it).segmentDelta);
 
-         
-      debug() << "dir=" << (*it).direction << " ms=" << (*it).movementSign
-              << " g=" << gradient;
-      
       if ((*it).direction.x < 0 || (*it).direction.z < 0)
          gradient *= -1.0f;
 
       gradient *= (*it).movementSign;
       
-      
       (*it).vehicle->update(delta, gradient);
    }
 
@@ -325,9 +320,11 @@ void Train::enterSegment(Part& aPart, const track::Connection& aConnection)
 {
    Point<int> pos;
    tie(pos, aPart.direction) = aConnection;
-   
-   //debug() << "Train part entered segment at " << pos
-   //        << " moving " << aPart.direction;
+
+#if 0
+   debug() << "Train part entered segment at " << pos
+           << " moving " << aPart.direction;
+#endif
 
    if (!map->isValidTrack(pos))
       throw runtime_error("Train fell off end of track!");
-- 
2.39.2