the-world-engine/dist/esm/box2d.ts/build/controllers/b2_buoyancy_controller.js

three.js based, unity like game engine for browser

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

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

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

import { b2Color } from "../common/b2_draw.js";

export class b2BuoyancyController extends b2Controller {
    constructor() {
        super(...arguments);
        this.normal = new b2Vec2(0, 1);
        this.offset = 0;
        this.density = 0;
        this.velocity = new b2Vec2(0, 0);
        this.linearDrag = 0;
        this.angularDrag = 0;
        this.useDensity = false;
        this.useWorldGravity = true;
        this.gravity = new b2Vec2(0, 0);
    }
    Step(t) {
        if (!this.m_bodyList) {
            return;
        }
        if (this.useWorldGravity) {
            this.gravity.Copy(this.m_bodyList.body.GetWorld().GetGravity());
        }
        for (let t = this.m_bodyList; t; t = t.nextBody) {
            const s = t.body;
            if (!s.IsAwake()) {
                continue;
            }
            const i = new b2Vec2;
            const o = new b2Vec2;
            let e = 0;
            let n = 0;
            for (let t = s.GetFixtureList(); t; t = t.m_next) {
                const h = new b2Vec2;
                const c = t.GetShape().ComputeSubmergedArea(this.normal, this.offset, s.GetTransform(), h);
                e += c;
                i.x += c * h.x;
                i.y += c * h.y;
                let r = 0;
                if (this.useDensity) {
                    r = t.GetDensity();
                } else {
                    r = 1;
                }
                n += c * r;
                o.x += c * h.x * r;
                o.y += c * h.y * r;
            }
            i.x /= e;
            i.y /= e;
            o.x /= n;
            o.y /= n;
            if (e < b2_epsilon) {
                continue;
            }
            const h = this.gravity.Clone().SelfNeg();
            h.SelfMul(this.density * e);
            s.ApplyForce(h, o);
            const c = s.GetLinearVelocityFromWorldPoint(i, new b2Vec2);
            c.SelfSub(this.velocity);
            c.SelfMul(-this.linearDrag * e);
            s.ApplyForce(c, i);
            s.ApplyTorque(-s.GetInertia() / s.GetMass() * e * s.GetAngularVelocity() * this.angularDrag);
        }
    }
    Draw(t) {
        const s = 100;
        const i = new b2Vec2;
        const o = new b2Vec2;
        i.x = this.normal.x * this.offset + this.normal.y * s;
        i.y = this.normal.y * this.offset - this.normal.x * s;
        o.x = this.normal.x * this.offset - this.normal.y * s;
        o.y = this.normal.y * this.offset + this.normal.x * s;
        const e = new b2Color(0, 0, .8);
        t.DrawSegment(i, o, e);
    }
}