Add angleTo

README.md

@@ -1,4 +1,5 @@
 # vec3
+
 [![NPM version](https://img.shields.io/npm/v/vec3.svg)](http://npmjs.com/package/vec3)
 [![Build Status](https://github.com/PrismarineJS/node-vec3/workflows/CI/badge.svg)](https://github.com/PrismarineJS/node-vec3/actions?query=workflow%3A%22CI%22)
 
@@ -7,7 +8,7 @@
 ## Usage
 
 ```js
-var v = require('vec3');
+var v = require("vec3");
 
 var v1 = v(1, 2, 3);
 console.log(v1); // prints "(1, 2, 3)"
@@ -18,7 +19,7 @@ console.log(v2); // prints "(1, 2, 4)"
 Or:
 
 ```js
-var Vec3 = require('vec3').Vec3;
+var Vec3 = require("vec3").Vec3;
 
 var v1 = new Vec3(1, 2, 3);
 // etc...
@@ -55,6 +56,7 @@ More available functions are listed below in Test Coverage.
     ✔ minus
     ✔ scaled
     ✔ abs
+    ✔ angleTo
     ✔ distanceTo
     ✔ distanceSquared
     ✔ equals

index.d.ts

@@ -126,6 +126,11 @@ export class Vec3 {
    */
   modulus(other: Vec3): Vec3;
 
+  /**
+   *  Return the angle in rad between another vector and this one
+   */
+  angleTo(other: Vec3): number;
+
   /**
    * Return the euclidean distance to another vector 
    */

index.js

@@ -133,6 +133,10 @@ class Vec3 {
       euclideanMod(this.z, other.z))
   }
 
+  angleTo (other) {
+    return Math.acos(this.dot(other) / (this.norm() * other.norm()))
+  }
+
   distanceTo (other) {
     const dx = other.x - this.x
     const dy = other.y - this.y

test/index.test-d.ts

@@ -39,6 +39,7 @@ expectType<Vec3>(vec.scaled(2));
 expectType<Vec3>(vec.abs());
 expectType<number>(vec.volume());
 expectType<Vec3>(vec.modulus(vec));
+expectType<number>(vec.angleTo(vec));
 expectType<number>(vec.distanceTo(vec));
 expectType<number>(vec.distanceSquared(vec));
 expectType<boolean>(vec.equals(vec));

test/test.js

@@ -182,6 +182,24 @@ describe('vec3', function () {
     assert.strictEqual(v2.y, 1.5)
     assert.strictEqual(v2.z, 1.9)
   })
+  it('angleTo', function () {
+    const v1 = new Vec3(1, 1, 1)
+    const v2 = new Vec3(1, 0, 0)
+    const angle1 = v1.angleTo(v2)
+    const angle2 = v2.angleTo(v1)
+    const expected = 0.9553166181
+    assert.strictEqual(angle1, angle2)
+    assert.strictEqual(Math.round(angle1 * 100000), Math.round(expected * 100000))
+  })
+  it('angleToNullVectors', function () {
+    const v1 = new Vec3(0, 0, 0)
+    const v2 = new Vec3(0, 0, 0)
+    const angle1 = v1.angleTo(v2)
+    const angle2 = v2.angleTo(v1)
+    const expected = NaN
+    assert.strictEqual(angle1, angle2)
+    assert.strictEqual(Math.round(angle1 * 100000), Math.round(expected * 100000))
+  })
   it('distanceTo', function () {
     const v1 = new Vec3(1, 1, 1)
     const v2 = new Vec3(2, 2, 2)