one step forward, one step back

math/path.ts

@@ -2,10 +2,12 @@ import { Vector } from "@bearmetal/doodler";
 
 export class ComplexPath {
   points: Vector[] = [];
+  segments: PathSegment[] = [];
 
   radius = 50;
 
   ctx?: CanvasRenderingContext2D;
+  evenPoints: Vector[] = [];
 
   constructor(points?: Vector[]) {
     points && (this.points = points);
@@ -35,6 +37,52 @@ export class ComplexPath {
     }
     ctx.restore();
   }
+
+  followEvenPoints(t: number) {
+    if (t < 0) t += this.evenPoints.length;
+    const i = Math.floor(t);
+    const a = this.evenPoints[i];
+    const b = this.evenPoints[(i + 1) % this.evenPoints.length];
+
+    return Vector.lerp(a, b, t % 1);
+  }
+
+  calculateEvenlySpacedPoints(spacing: number, resolution = 1) {
+    // this.pointSpacing = 1;
+    // return this.segments.flatMap(s => s.calculateEvenlySpacedPoints(spacing, resolution));
+    const points: Vector[] = [];
+
+    points.push(this.segments[0].points[0]);
+    let prev = points[0];
+    let distSinceLastEvenPoint = 0;
+    for (const seg of this.segments) {
+      let t = 0;
+
+      const div = Math.ceil(seg.length * resolution * 10);
+      while (t < 1) {
+        t += 1 / div;
+        const point = seg.getPointAtT(t);
+        distSinceLastEvenPoint += prev.dist(point);
+
+        if (distSinceLastEvenPoint >= spacing) {
+          const overshoot = distSinceLastEvenPoint - spacing;
+          const evenPoint = Vector.add(
+            point,
+            Vector.sub(point, prev).normalize().mult(overshoot),
+          );
+          distSinceLastEvenPoint = overshoot;
+          points.push(evenPoint);
+          prev = evenPoint;
+        }
+
+        prev = point;
+      }
+    }
+
+    this.evenPoints = points;
+
+    return points;
+  }
 }
 
 export class PathSegment {
@@ -43,6 +91,9 @@ export class PathSegment {
   length: number;
   startingLength: number;
 
+  next?: PathSegment;
+  prev?: PathSegment;
+
   constructor(points: [Vector, Vector, Vector, Vector]) {
     this.points = points;
     this.length = this.calculateApproxLength(100);
@@ -254,4 +305,6 @@ export class PathSegment {
       this.points[3].set(points[curveLength]);
     }
   }
+
+  draw(): void {}
 }