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import { System } from '@serpentity/serpentity';
const internals = {
kTightStiffness: 0.001,
kBaseStiffness: 0.0008,
kLooseStiffness: 0.0000001
};
import ElasticNode from '../nodes/elastic';
/**
Changes the stiffness on the node when it's less extended
*
* @extends {external:Serpentity.System}
* @class ElasticSystem
* @param {object} config a configuration object to extend.
*/
export default class ElasticSystem extends System {
constructor(config = {}) {
super();
/**
* The node collection of entities that have external force
*
* @property {external:Serpentity.NodeCollection} elastics
* @instance
* @memberof ElasticSystem
*/
this.elastics = null;
}
/**
* Initializes system when added. Requests elastic nodes
*
* @function added
* @memberof ElasticSystem
* @instance
* @param {external:Serpentity.Engine} engine the serpentity engine to
* which we are getting added
*/
added(engine) {
this.elastics = engine.getNodes(ElasticNode);
}
/**
* Clears system resources when removed.
*
* @function removed
* @instance
* @memberof ElasticSystem
*/
removed() {
this.elastics = null;
}
/**
* Runs on every update of the loop. Checks length of elastic and adjusts
* stiffness
*
* @function update
* @instance
* @param {Number} currentFrameDuration the duration of the current
* frame
* @memberof ElasticSystem
*/
update(currentFrameDuration) {
for (const elastic of this.elastics) {
const constraint = elastic.body.body;
const currentDistance = Math.abs(
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) {
constraint.stiffness = internals.kLooseStiffness;
continue;
}
if (currentDistance >= 2.6 * constraint.length) {
constraint.stiffness = internals.kTightStiffness;
continue;
}
constraint.stiffness = internals.kBaseStiffness;
}
}
}
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