final steps, change color

ikjoint.js

@@ -0,0 +1,98 @@
+let vec = p5.Vector
+class IKJoint {
+  constructor(numSegments, pointDist) {
+    this.origin = new vec(0, 0);
+    this.points = [];
+    for (let i = 0; i < numSegments + 1; i++) {
+      this.points.push(new ConstraintPoint(0, 0, pointDist, 1.3));
+    }
+    this.pointDist = pointDist;
+    this.iterations = 20;
+  }
+
+  moveStart(targetX, targetY) {
+    let numPts = this.points.length;
+    this.points[0].size = 1;
+    this.points[0].follow(targetX, targetY);
+
+    for (let i = 1; i < numPts; i++) {
+      let prevPoint = this.points[i - 1];
+      this.points[i].follow(prevPoint.pos.x, prevPoint.pos.y, prevPoint.forward);
+    }
+  }
+
+  moveEnd(targetX, targetY) {
+    let numPts = this.points.length;
+    this.points[numPts - 1].pos.x = targetX;
+    this.points[numPts - 1].pos.y = targetY;
+
+    for (let i = numPts - 2; i >= 0; i--) {
+      let prevPoint = this.points[i + 1];
+      this.points[i].follow(prevPoint.pos.x, prevPoint.pos.y, null);
+    }
+  }
+
+  moveTo(origX, origY, targetX, targetY) {
+    for (let i = 0; i < this.iterations; i++) {
+      this.moveEnd(targetX, targetY);
+      this.moveStart(origX, origY);
+    }
+  }
+}
+
+class ConstraintPoint {
+  constructor(x, y, size, angleConstraint = 0.2) {
+    this.size = size;
+    this.pos = new vec(x, y);
+    this.forward = new vec(0, 0);
+    this.angleConstraint = angleConstraint;
+  }
+
+  getRel(angleOffset, dist) {
+    let dir = vec.rotate(this.forward, angleOffset);
+    dir.setMag(dist);
+    return vec.add(this.pos, dir);
+  }
+
+  follow(targetX, targetY, parentForward = null) {
+    let target = new vec(targetX, targetY);
+    let targetForward = vec.sub(target, this.pos);
+    let targetAngle = targetForward.heading();
+
+    if (parentForward) {
+      let parentAngle = parentForward.heading();
+      let diff = targetAngle - parentAngle;
+
+      while (diff < -PI) diff += TWO_PI;
+      while (diff > PI) diff -= TWO_PI;
+
+      let maxAngle = this.angleConstraint;
+      diff = constrain(diff, -maxAngle, maxAngle);
+
+      targetAngle = parentAngle + diff;
+    }
+
+    this.forward = p5.Vector.fromAngle(targetAngle);
+
+    let dir = p5.Vector.mult(this.forward, -this.size);
+    this.pos = vec.add(target, dir);
+  }
+}
+
+let ik = new IKJoint(8, 20);
+function setup() {
+	createCanvas(400, 400);
+}
+
+function draw() {
+  background(220);
+	ik.moveTo(200, 200, mouseX, mouseY);
+
+	for (let i = 0;i < 8;i++) {
+		let p = ik.points[i].pos
+		noFill();
+		circle(p.x, p.y, 20);
+	}
+
+}
+