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

 import { System } from '@serpentity/serpentity';

3 const internals = {

4 kTightStiffness: 0.001,

5 kBaseStiffness: 0.0008,

6 kLooseStiffness: 0.0000001

7 };

9 import ElasticNode from '../nodes/elastic';

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 {

20 constructor(config = {}) {

22 super();

24 /**

25 * The node collection of entities that have external force

26 *

27 * @property {external:Serpentity.NodeCollection} elastics

28 * @instance

29 * @memberof ElasticSystem

30 */

     this.elastics = null;

32 }

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) {

     this.elastics = engine.getNodes(ElasticNode);

46 }

48 /**

49 * Clears system resources when removed.

50 *

51 * @function removed

52 * @instance

53 * @memberof ElasticSystem

54 */

55 removed() {

     this.elastics = null;

58 }

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) {

     for (const elastic of this.elastics) {

       const constraint = elastic.body.body;

       const currentDistance = Math.abs(

76 Math.sqrt(

           Math.pow(constraint.bodyA.position.x - constraint.bodyB.position.x, 2) +

           Math.pow(constraint.bodyA.position.y - constraint.bodyB.position.y, 2)));

       if (currentDistance <= constraint.length) {

81 constraint.stiffness = internals.kLooseStiffness;

82 continue;

83 }

       if (currentDistance >= 2.6 * constraint.length) {

86 constraint.stiffness = internals.kTightStiffness;

87 continue;

88 }

90 constraint.stiffness = internals.kBaseStiffness;

91 }

92 }

93 }