tracing

docs/chapters/tracing/distance-function.js

@@ -0,0 +1,46 @@
+let curve;
+
+setup(api) {
+  curve = new Bezier(this, 65, 150, 15, 35, 175, 245, 35, 140);
+  setMovable(curve.points);
+}
+
+draw() {
+  resetTransform();
+  clear();
+
+  curve.drawSkeleton();
+  curve.drawCurve();
+  curve.drawPoints();
+
+  let w = this.width/2;
+  let h = this.height;
+  let len = curve.length();
+
+  translate(w,0);
+  line(0, 0, 0, h);
+  scale(0.85);
+  translate(30,30);
+
+  setStroke(`black`);
+  drawAxes("t", 0, 1, "d", 0, len|0, w, h);
+  this.plotDistanceFunction(w, h, len);
+}
+
+plotDistanceFunction(w, h, len) {
+  noFill();
+  let LUT = curve.getLUT(this.steps * 10);
+  let d = 0;
+  start();
+  vertex(0,0);
+  for(let i=1, e=LUT.length, p1, p2; i<e; i++) {
+    p1 = LUT[i-1];
+    p2 = LUT[i];
+    d += dist(p1.x, p1.y, p2.x, p2.y);
+    vertex(
+      map(i, 0, e, 0, w),
+      map(d, 0, len, 0, h)
+    );
+  }
+  end();
+}