gravity = id="gravity_value">1.0 id="gravity_value">     
...
var camera, scene, renderer;  var geometry, material, mesh;  var gravity = 1.0; 2.0;  var ground_position = -220;  var half_world_width = 500;  var simulation_stopped = true; 
...
renderer.render( scene, camera );  }  function update_world() { 
...
if( (mesh.position.y < ground_position) ){ mesh.speed.y = -mesh.speed.y;  }  else{  mesh.speed.y -= $("#gravity_slider").slider("value"); gravity;  }  if( (mesh.position.x < -half_world_width) || (mesh.position.x > half_world_width) ){ 
...
}  $(function() {  $( "#gravity_value" ).html( gravity);   $(  "#gravity_slider" ).slider({ min: 0.0, max:10.0, value: 1.0, gravity,  step: 0.1 0.1, slide: function( event, ui ) {   $( "#gravity_value" ).html( ui.value);   gravity = ui.value;   }  }); });