calculate single-object effect on spacetime plane (with three.js PlaneGeometry)

gravity.js

var G = 100;
var vertex;

for (var i = 0; i < plane.geometry.vertices.length; i++) {
  vertex = plane.geometry.vertices[i];
  var distance = Math.sqrt(Math.pow(vertex.x - sphere.position.x, 2) + Math.pow(vertex.y - -sphere.position.z, 2));
  var f = -(G * sphere.mass) / Math.pow(distance, 2);
  vertex.z = f;
}