physics.look-in-vector-direction.spec.js

import { lookInVectorDirection } from "./physics.js";

const sinCos45deg = 0.7071;

describe("physics", () => {
  describe("lookInVectorDirection()", () => {
    it("rotates π/2 rad around the y-axis when the vector is pointing right", () => {
      const vector = { x: 1.0, y: 0.0, z: 0.0 };
      const object = withoutRotation();

      lookInVectorDirection(object, vector);

      expect(object.rotation.x).toBe(0);
      expect(object.rotation.y).toBe(Math.PI / 2.0);
      expect(object.rotation.z).toBe(0);
    });

    it("rotates π/4 rad around the y-axis when the vector is pointing right and forward", () => {
      const vector = { x: sinCos45deg, y: 0.0, z: sinCos45deg };
      const object = withoutRotation();

      lookInVectorDirection(object, vector);

      expect(object.rotation.x).toBe(0);
      expect(round4(object.rotation.y)).toBe(round4(Math.PI / 4.0));
      expect(object.rotation.z).toBe(0);
    });

    it("rotates 3π/4 rad around the y-axis when the vector is pointing right and back", () => {
      const vector = { x: sinCos45deg, y: 0.0, z: -sinCos45deg };
      const object = withoutRotation();

      lookInVectorDirection(object, vector);

      expect(object.rotation.x).toBe(0);
      expect(round4(object.rotation.y)).toBe(round4((3.0 * Math.PI) / 4.0));
      expect(object.rotation.z).toBe(0);
    });

    it("rotates 5π/4 rad around the y-axis when the vector is pointing left and back", () => {
      const vector = { x: -sinCos45deg, y: 0.0, z: -sinCos45deg };
      const object = withoutRotation();

      lookInVectorDirection(object, vector);

      expect(object.rotation.x).toBe(0);
      expect(round4(object.rotation.y)).toBe(round4((5.0 * Math.PI) / 4.0));
      expect(object.rotation.z).toBe(0);
    });

    it("rotates 7π/4 rad around the y-axis when the vector is pointing left and forward", () => {
      const vector = { x: -sinCos45deg, y: 0.0, z: sinCos45deg };
      const object = withoutRotation();

      lookInVectorDirection(object, vector);

      expect(object.rotation.x).toBe(0);
      expect(object.rotation.y).toBe((7.0 * Math.PI) / 4.0);
      expect(object.rotation.z).toBe(0);
    });

    it("doesn't update rotation when vector length is 0", () => {
      const vector = { x: 0.0, y: 0.0, z: 0.0 };
      const initialRotation = Math.PI / 7.0;
      const object = { rotation: { x: 0.0, y: initialRotation, z: 0.0 } };

      lookInVectorDirection(object, vector);

      expect(object.rotation.x).toBe(0);
      expect(object.rotation.y).toBe(initialRotation);
      expect(object.rotation.z).toBe(0);
    });
  });
});

function withoutRotation() {
  return { rotation: { x: 0.0, y: 0.0, z: 0.0 } };
}

function round4(n) {
  return Math.round(n * 10000.0) / 10000.0;
}