incheon/src/physics/SimplePhysicsEngine.js

A Node.js based real-time game server

'use strict';
const PhysicsEngine = require('./PhysicsEngine');
const CollisionDetection = require('./SimplePhysics/CollisionDetection');
const TwoVector = require('../serialize/TwoVector');

let dv = new TwoVector();
/**
 * SimplePhysicsEngine is a pseudo-physics engine which works with
 * objects of class DynamicObject.
 */
class SimplePhysicsEngine extends PhysicsEngine {

    init(initOptions) {
        super.init(initOptions);
        this.collisionDetection = new CollisionDetection();

        let collisionOptions = Object.assign({ gameEngine: this.gameEngine }, initOptions.collisionOptions);
        this.collisionDetection.init(collisionOptions);
    }

    // a single object advances, based on:
    // isRotatingRight, isRotatingLeft, isAccelerating, current velocity
    // wrap-around the world if necessary
    objectStep(o) {
        let worldSettings = this.gameEngine.worldSettings;

        if (o.isRotatingRight) { o.angle += o.rotationSpeed; }
        if (o.isRotatingLeft) { o.angle -= o.rotationSpeed; }

        if (o.angle >= 360) { o.angle -= 360; }
        if (o.angle < 0) { o.angle += 360; }

        if (o.isAccelerating) {
            let rad = o.angle * (Math.PI / 180);
            dv.set(Math.cos(rad), Math.sin(rad)).multiplyScalar(o.acceleration);
            o.velocity.add(dv);
        }

        // o.velX = Math.round(o.velX * 100) / 100;
        // o.velY = Math.round(o.velY * 100) / 100;

        let velMagnitude = o.velocity.length();
        if ((o.maxSpeed !== null) && (velMagnitude > o.maxSpeed)) {
            o.velocity.multiplyScalar(o.maxSpeed / velMagnitude);
        }

        o.isAccelerating = false;
        o.isRotatingLeft = false;
        o.isRotatingRight = false;

        o.position.add(o.velocity);

        // wrap around the world edges
        if (worldSettings.worldWrap) {
            if (o.position.x >= worldSettings.width) { o.position.x -= worldSettings.width; }
            if (o.position.y >= worldSettings.height) { o.position.y -= worldSettings.height; }
            if (o.position.x < 0) { o.position.x += worldSettings.width; }
            if (o.position.y < 0) { o.position.y += worldSettings.height; }
        }
    }

    // entry point for a single step of the Simple Physics
    step(objectFilter) {

        // each object should advance
        let objects = this.gameEngine.world.objects;
        for (let objId of Object.keys(objects)) {

            // shadow objects are not re-enacted
            let ob = objects[objId];
            if (!objectFilter(ob))
                continue;

            // run the object step
            this.objectStep(ob);
        }

        // emit event on collision
        this.collisionDetection.detect(this.gameEngine);
    }
}

module.exports = SimplePhysicsEngine;