flow like the river

VISUALIZACION/node_modules/ngraph.forcelayout/lib/kdForce.js

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+/**
+ * This is not used anywhere, but it is a good exploration into kd-tree based
+ * simulation.
+ */
+module.exports = createKDForce;
+
+function createKDForce(bodies, settings) {
+  var KDBush = require('kdbush').default;
+  var random = require('ngraph.random').random(1984);
+
+  return kdForce;
+
+  function kdForce(iterationNumber) {
+    if (iterationNumber < 500) return;
+    var gravity = settings.gravity;
+    var points = new KDBush(bodies, p => p.pos.x0, p => p.pos.x1);
+    var i = bodies.length;
+    while (i--) {
+      var body = bodies[i];
+      body.reset();
+      var neighbors = points.within(body.pos.x0, body.pos.x1, settings.springLength);
+      var fx = 0, fy = 0;
+      for (var j = 0; j < neighbors.length; ++j) {
+        var other = bodies[neighbors[j]];
+        if (other === body) continue;
+
+        var dx = other.pos.x0 - body.pos.x0;
+        var dy = other.pos.x1 - body.pos.x1;
+        var r = Math.sqrt(dx * dx + dy * dy);
+        if (r === 0) {
+          // Poor man's protection against zero distance.
+          dx = (random.nextDouble() - 0.5) / 50;
+          dy = (random.nextDouble() - 0.5) / 50;
+          r = Math.sqrt(dx * dx + dy * dy);
+        }
+        var v = gravity * other.mass * body.mass / (r * r * r);
+        fx += v * dx;
+        fy += v * dy;
+      }
+      body.force.x0 = fx;
+      body.force.x1 = fy;
+      //dragForce.update(body);
+    }
+  }
+}