2.1 Implement test track drawing

2 files changed, 71 insertions, 9 deletions

diff --git a/src/BetterBase.java b/src/BetterBase.java
index 2e233ee..9ae499a 100644
--- a/src/BetterBase.java
+++ b/src/BetterBase.java
@@ -3,6 +3,7 @@ import com.jogamp.opengl.util.gl2.GLUT;
 import javax.media.opengl.GL2;
 import javax.media.opengl.glu.GLU;
 import java.awt.Color;
+import robotrace.Vector;
 
 /**
  * Base class that provides basic bindings to the ugly JOGL interface. This
@@ -46,4 +47,13 @@ abstract class BetterBase {
         float[] rgba = color.getRGBComponents(null);
         gl.glColor3fv(rgba, 0);
     }
+
+    /**
+     * Pass a vector as a vertex to OpenGL.
+     */
+    static public void glVertex(Vector vector) {
+        gl.glVertex3d(vector.x(),
+                      vector.y(),
+                      vector.z());
+    }
 }
diff --git a/src/RaceTrack.java b/src/RaceTrack.java
index 78e6e89..d40c529 100644
--- a/src/RaceTrack.java
+++ b/src/RaceTrack.java
@@ -1,20 +1,26 @@
 
 import robotrace.Vector;
 import static java.lang.Math.*;
+import static javax.media.opengl.GL2.*;
 
 /**
  * Implementation of a race track that is made from Bezier segments.
  */
-class RaceTrack {
+class RaceTrack extends BetterBase {
     /**
-     * Halfwidth of the ellipse.
+     * Half-width of the ellipse.
      */
-    protected static final int ELLIPSE_A = 10;
+    protected static final double ELLIPSE_A = 10;
 
     /**
-     * Halfheight of the ellipse. 
+     * Half-height of the ellipse.
      */
-    protected static final int ELLIPSE_B = 14;
+    protected static final double ELLIPSE_B = 14;
+
+    /**
+     * Number of segments for the race track.
+     */
+    private final double SEGMENTS = 180;
 
     /**
      * Array with control points for the O-track.
@@ -52,7 +58,7 @@ class RaceTrack {
 
         // The test track is selected
         if (0 == trackNr) {
-            // code goes here ...
+            drawTestTrack();
         } else if (1 == trackNr) { // The O-track is selected
             // code goes here ...
         } else if (2 == trackNr) { // The L-track is selected
@@ -94,9 +100,55 @@ class RaceTrack {
          * describes the tangent vector of point p. 
          */
         Vector p = getPoint(t);
-        
-        return new Vector(-p.y()/(ELLIPSE_A * ELLIPSE_A),
-                          p.x()/(ELLIPSE_B * ELLIPSE_B),
+        return new Vector(-p.y() / (ELLIPSE_A * ELLIPSE_A),
+                          p.x() / (ELLIPSE_B * ELLIPSE_B),
                           0).normalized();
     }
+
+    private void drawTestTrack() {
+        /* A track segment looks like:
+         *         B----------------------------D
+         *       / :                           /|
+         *     /   G- - - - - - - - - - - - -/--H
+         *   /                            /
+         * A----------------------------C
+         * |                            |
+         * E----------------------------F
+         * ^-- t = t0                   ^-- t = t0 + 1
+         * Assume point A the inner point of the race track. Draw quads from
+         * EF (starting point) to AC, BD, GH.
+         */
+        // previous points
+        Vector point_A = null, point_B = null, point_E = null, point_G = null;
+
+        for (double i = 0; i < SEGMENTS; ++i) {
+            double t = i * 2 * PI / SEGMENTS;
+            Vector point_C = getPoint(t);
+            Vector lanes_len = getTangent(t).cross(point_C).normalized().scale(4);
+            Vector point_D = point_C.add(lanes_len);
+            // Z=1 to Z=-1
+            Vector point_F = point_C.subtract(new Vector(0, 0, 2));
+            Vector point_H = point_D.subtract(new Vector(0, 0, 2));
+
+            // initially, there are no "previous" vectors to use as start.
+            if (i > 0) {
+                gl.glBegin(GL_QUAD_STRIP);
+                glVertex(point_E);
+                glVertex(point_F);
+                glVertex(point_A);
+                glVertex(point_C);
+                glVertex(point_B);
+                glVertex(point_D);
+                glVertex(point_G);
+                glVertex(point_H);
+                gl.glEnd();
+            }
+
+            // save points for next draw round
+            point_E = point_F;
+            point_A = point_C;
+            point_B = point_D;
+            point_G = point_H;
+        }
+    }
 }