gibbon.js/lib/src/components/dest-accel.js

Actor/Component system for use with pixi.js.

import { Component } from '../core/component';
import { Point } from 'pixi.js';
import { Mover } from './mover';
/**
 * Uses mover component to accelerate towards a destination point
 * and deccelerate upon arrival.
 */
export class DestAccel extends Component {
    dest = new Point();
    /**
     * Radius at which to attempt to stop.
     * todo: compute from current move velocity and acceleration?
     */
    stopRadius = 40;
    /**
     * Radius at which actor should slow down.
     */
    slowRadius = 150;
    mover;
    setDest(pt) {
        this.dest.set(pt.x, pt.y);
    }
    init() {
        this.mover = this.require(Mover);
        this.dest.copyFrom(this.position);
    }
    update(delta) {
        const pt = this.position;
        const dx = this.dest.x - pt.x;
        const dy = this.dest.y - pt.y;
        const d = dx * dx + dy * dy;
        if (d < (this.stopRadius * this.stopRadius)) {
            const v = this.mover.velocity;
            /// arrive.
            this.mover.accel.set(-v.x, -v.y);
        }
        else if (d < this.slowRadius * this.slowRadius) {
            const vx = this.mover.velocity.x;
            const vy = this.mover.velocity.y;
            // targetV - currentV
            const deltaV = (Math.sqrt(d) / this.slowRadius) * this.mover.velocityMax
                - Math.sqrt(vx * vx + vy * vy);
            this.mover.accel.set(deltaV * dx, deltaV * dy);
        }
        else {
            // acceleration cap is handled in mover.
            this.mover.accel.set(this.mover.accelMax * dx, this.mover.accelMax * dy);
        }
    }
}
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