From d5c93f956ecfa3a4b4811190f7106540a41fa8f7 Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Sun, 10 Apr 2011 20:41:52 +0100
Subject: [PATCH] Some tweaks to GenTrack curve function

---
 include/BezierCurve.hpp |  4 ++--
 src/GenTrack.cpp        | 22 ++++++++++++++++++++--
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/include/BezierCurve.hpp b/include/BezierCurve.hpp
index ea4e29d..9025fc1 100644
--- a/include/BezierCurve.hpp
+++ b/include/BezierCurve.hpp
@@ -25,7 +25,7 @@
 template <typename T>
 struct BezierCurve {
    Vector<T> p[4];
-   T length;  // A very rough approximation to the length
+   T length;  // Approximate
 
    BezierCurve(Vector<T> p1, Vector<T> p2, Vector<T> p3, Vector<T> p4)
    {
@@ -82,7 +82,7 @@ struct BezierCurve {
    }
 
    // A slower approximation to the curve function that guarantees
-   // uniform(k).length() = curve_length * k
+   // a linear relationship between s and the arc length
    Vector<T> uniform(T s, T *out = NULL) const
    {
       Vector<T> cur = operator()(0.0), prev;
diff --git a/src/GenTrack.cpp b/src/GenTrack.cpp
index 06acc34..174202b 100644
--- a/src/GenTrack.cpp
+++ b/src/GenTrack.cpp
@@ -111,8 +111,8 @@ GenTrack::GenTrack(Vector<int> delta,
    const float exit_extend = extend_from_center(exit_dir);
 
    Vector<float> p1 = entry_dir_norm * -entry_extend;
-   Vector<float> p2 = entry_dir_norm * pinch_length;
-   Vector<float> p3 = delta_f - (exit_dir_norm * pinch_length);
+   Vector<float> p2 = entry_dir_norm * (pinch_length - entry_extend);
+   Vector<float> p3 = delta_f - (exit_dir_norm * (pinch_length - exit_extend));
    Vector<float> p4 = delta_f + (exit_dir_norm * exit_extend);
 
    curve = make_bezier_curve(p1, p2, p3, p4);
@@ -195,6 +195,24 @@ void GenTrack::render() const
 
    glPopMatrix();
 #endif
+
+#if 1
+   // Draw control points
+   glPushMatrix();
+   glPushAttrib(GL_LINE_BIT);
+
+   glTranslatef(origin.x, 0.0f, origin.y);
+   glColor3f(0.8f, 0.1f, 0.1f);
+   glLineWidth(4.0f);
+
+   glBegin(GL_LINES);
+   for (int i = 0; i < 4; i++)
+      gl::vertex(curve.p[i] + make_vector(0.0f, 0.2f, 0.0f));
+   glEnd();
+
+   glPopAttrib();
+   glPopMatrix();
+#endif
 }     
 
 void GenTrack::set_origin(int x, int y, float h)
-- 
2.39.2