git.r.bdr.sh - rbdr/sumo/blob - lib/systems/elastic.js

   1 import { System } from '@serpentity/serpentity';
   2
   3 const internals = {
   4   kTightStiffness: 0.001,
   5   kBaseStiffness: 0.0008,
   6   kLooseStiffness: 0.0000001
   7 };
   8
   9 import ElasticNode from '../nodes/elastic';
  10
  11 /**
  12  Changes the stiffness on the node when it's less extended
  13  *
  14  * @extends {external:Serpentity.System}
  15  * @class ElasticSystem
  16  * @param {object} config a configuration object to extend.
  17  */
  18 export default class ElasticSystem extends System {
  19
  20   constructor(config = {}) {
  21
  22     super();
  23
  24     /**
  25      * The node collection of entities that have external force
  26      *
  27      * @property {external:Serpentity.NodeCollection} elastics
  28      * @instance
  29      * @memberof ElasticSystem
  30      */
  31     this.elastics = null;
  32   }
  33
  34   /**
  35    * Initializes system when added. Requests elastic nodes
  36    *
  37    * @function added
  38    * @memberof ElasticSystem
  39    * @instance
  40    * @param {external:Serpentity.Engine} engine the serpentity engine to
  41    * which we are getting added
  42    */
  43   added(engine) {
  44
  45     this.elastics = engine.getNodes(ElasticNode);
  46   }
  47
  48   /**
  49    * Clears system resources when removed.
  50    *
  51    * @function removed
  52    * @instance
  53    * @memberof ElasticSystem
  54    */
  55   removed() {
  56
  57     this.elastics = null;
  58   }
  59
  60   /**
  61    * Runs on every update of the loop. Checks length of elastic and adjusts
  62    * stiffness
  63    *
  64    * @function update
  65    * @instance
  66    * @param {Number} currentFrameDuration the duration of the current
  67    * frame
  68    * @memberof ElasticSystem
  69    */
  70   update(currentFrameDuration) {
  71
  72     for (const elastic of this.elastics) {
  73       const constraint = elastic.body.body;
  74
  75       const currentDistance = Math.abs(
  76         Math.sqrt(
  77           Math.pow(constraint.bodyA.position.x - constraint.bodyB.position.x, 2) +
  78           Math.pow(constraint.bodyA.position.y - constraint.bodyB.position.y, 2)));
  79
  80       if (currentDistance <= constraint.length) {
  81         constraint.stiffness = internals.kLooseStiffness;
  82         continue;
  83       }
  84
  85       if (currentDistance >= 2.6 * constraint.length) {
  86         constraint.stiffness = internals.kTightStiffness;
  87         continue;
  88       }
  89
  90       constraint.stiffness = internals.kBaseStiffness;
  91     }
  92   }
  93 };