the-world-engine/dist/esm/box2d.ts/build/controllers/b2_gravity_controller.js

three.js based, unity like game engine for browser

import { b2Controller } from "./b2_controller.js";

import { b2_epsilon } from "../common/b2_settings.js";

import { b2Sqrt, b2Vec2 } from "../common/b2_math.js";

export class b2GravityController extends b2Controller {
    constructor() {
        super(...arguments);
        this.G = 1;
        this.invSqr = true;
    }
    Step(t) {
        if (this.invSqr) {
            for (let t = this.m_bodyList; t; t = t.nextBody) {
                const o = t.body;
                const s = o.GetWorldCenter();
                const n = o.GetMass();
                for (let r = this.m_bodyList; r && r !== t; r = r.nextBody) {
                    const t = r.body;
                    const c = t.GetWorldCenter();
                    const i = t.GetMass();
                    const e = c.x - s.x;
                    const l = c.y - s.y;
                    const b = e * e + l * l;
                    if (b < b2_epsilon) {
                        continue;
                    }
                    const f = b2GravityController.Step_s_f.Set(e, l);
                    f.SelfMul(this.G / b / b2Sqrt(b) * n * i);
                    if (o.IsAwake()) {
                        o.ApplyForce(f, s);
                    }
                    if (t.IsAwake()) {
                        t.ApplyForce(f.SelfMul(-1), c);
                    }
                }
            }
        } else {
            for (let t = this.m_bodyList; t; t = t.nextBody) {
                const o = t.body;
                const s = o.GetWorldCenter();
                const n = o.GetMass();
                for (let r = this.m_bodyList; r && r !== t; r = r.nextBody) {
                    const t = r.body;
                    const c = t.GetWorldCenter();
                    const i = t.GetMass();
                    const e = c.x - s.x;
                    const l = c.y - s.y;
                    const b = e * e + l * l;
                    if (b < b2_epsilon) {
                        continue;
                    }
                    const f = b2GravityController.Step_s_f.Set(e, l);
                    f.SelfMul(this.G / b * n * i);
                    if (o.IsAwake()) {
                        o.ApplyForce(f, s);
                    }
                    if (t.IsAwake()) {
                        t.ApplyForce(f.SelfMul(-1), c);
                    }
                }
            }
        }
    }
    Draw(t) {}
}

b2GravityController.Step_s_f = new b2Vec2;