correct the random() method (#27724)

src/math/Quaternion.js

@@ -591,23 +591,24 @@ class Quaternion {
 
 	random() {
 
-		// Derived from http://planning.cs.uiuc.edu/node198.html
-		// Note, this source uses w, x, y, z ordering,
-		// so we swap the order below.
+		// sets this quaternion to a uniform random unit quaternnion
 
-		const u1 = Math.random();
-		const sqrt1u1 = Math.sqrt( 1 - u1 );
-		const sqrtu1 = Math.sqrt( u1 );
+		// Ken Shoemake
+		// Uniform random rotations
+		// D. Kirk, editor, Graphics Gems III, pages 124-132. Academic Press, New York, 1992.
 
-		const u2 = 2 * Math.PI * Math.random();
+		const theta1 = 2 * Math.PI * Math.random();
+		const theta2 = 2 * Math.PI * Math.random();
 
-		const u3 = 2 * Math.PI * Math.random();
+		const x0 = Math.random();
+		const r1 = Math.sqrt( 1 - x0 );
+		const r2 = Math.sqrt( x0 );
 
 		return this.set(
-			sqrt1u1 * Math.cos( u2 ),
-			sqrtu1 * Math.sin( u3 ),
-			sqrtu1 * Math.cos( u3 ),
-			sqrt1u1 * Math.sin( u2 ),
+			r1 * Math.sin( theta1 ),
+			r1 * Math.cos( theta1 ),
+			r2 * Math.sin( theta2 ),
+			r2 * Math.cos( theta2 ),
 		);
 
 	}