planck-js/src/dynamics/joint/__test__/DistanceJoint.test.ts

2D JavaScript/TypeScript physics engine for cross-platform HTML5 game development

import { describe, it, expect } from "vitest";

import { Vec2 } from "../../../common/Vec2";
import { CircleShape } from "../../../collision/shape/CircleShape";
import { BoxShape } from "../../../collision/shape/BoxShape";
import { World } from "../../World";

import { DistanceJoint } from "../DistanceJoint";

describe("DistanceJoint", function(): void {

  it("calculates local anchors from global", function(): void {
    var world = new World();

    var circle = new CircleShape(1);
    var box = new BoxShape(1, 1);

    var b1 = world.createBody({
      position : new Vec2(0, 0),
      type : "dynamic"
    });
    b1.createFixture(circle);

    var b2 = world.createBody({
      position : new Vec2(10, 0),
      type : "dynamic"
    });
    b2.createFixture(box);

    var joint = new DistanceJoint({}, b1, b2, new Vec2(1, 0), new Vec2(9, -1));
    world.createJoint(joint);

    expect(joint.getLocalAnchorA()).deep.equal(new Vec2(1, 0));
    expect(joint.getLocalAnchorB()).deep.equal(new Vec2(-1, -1));

    expect(joint.getAnchorA()).deep.equal(new Vec2(1, 0));
    expect(joint.getAnchorB()).deep.equal(new Vec2(9, -1));

  });

  it("moves attached body", function(): void {
    var world = new World();

    var circle = new CircleShape(1);
    var box = new BoxShape(1, 1);

    var b1 = world.createBody({
      position : new Vec2(0, 0),
      type : "dynamic"
    });
    b1.createFixture(circle);

    var b2 = world.createBody({
      position : new Vec2(10, 0),
      type : "dynamic"
    });
    b2.createFixture(box);

    var joint = new DistanceJoint({}, b1, b2, new Vec2(1, 0), new Vec2(9, -1));
    world.createJoint(joint);

    b2.applyForceToCenter(new Vec2(500, 0), true);
    world.step(1 / 10);

    expect(b1.getPosition().x).closeTo(2, 1e-1);
    expect(b2.getPosition().x).closeTo(12, 1e-1);
  });

});