noise( xin, yin ) {

		let n0; // Noise contributions from the three corners
		let n1;
		let n2;
		// Skew the input space to determine which simplex cell we're in
		const F2 = 0.5 * ( Math.sqrt( 3.0 ) - 1.0 );
		const s = ( xin + yin ) * F2; // Hairy factor for 2D
		const i = Math.floor( xin + s );
		const j = Math.floor( yin + s );
		const G2 = ( 3.0 - Math.sqrt( 3.0 ) ) / 6.0;
		const t = ( i + j ) * G2;
		const X0 = i - t; // Unskew the cell origin back to (x,y) space
		const Y0 = j - t;
		const x0 = xin - X0; // The x,y distances from the cell origin
		const y0 = yin - Y0;

		// For the 2D case, the simplex shape is an equilateral triangle.
		// Determine which simplex we are in.
		let i1; // Offsets for second (middle) corner of simplex in (i,j) coords

		let j1;
		if ( x0 > y0 ) {

			i1 = 1; j1 = 0;

			// lower triangle, XY order: (0,0)->(1,0)->(1,1)

		}	else {

			i1 = 0; j1 = 1;

		} // upper triangle, YX order: (0,0)->(0,1)->(1,1)

		// A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
		// a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
		// c = (3-sqrt(3))/6
		const x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
		const y1 = y0 - j1 + G2;
		const x2 = x0 - 1.0 + 2.0 * G2; // Offsets for last corner in (x,y) unskewed coords
		const y2 = y0 - 1.0 + 2.0 * G2;
		// Work out the hashed gradient indices of the three simplex corners
		const ii = i & 255;
		const jj = j & 255;
		const gi0 = this.perm[ ii + this.perm[ jj ] ] % 12;
		const gi1 = this.perm[ ii + i1 + this.perm[ jj + j1 ] ] % 12;
		const gi2 = this.perm[ ii + 1 + this.perm[ jj + 1 ] ] % 12;
		// Calculate the contribution from the three corners
		let t0 = 0.5 - x0 * x0 - y0 * y0;
		if ( t0 < 0 ) n0 = 0.0;
		else {

			t0 *= t0;
			n0 = t0 * t0 * this._dot( this.grad3[ gi0 ], x0, y0 ); // (x,y) of grad3 used for 2D gradient

		}

		let t1 = 0.5 - x1 * x1 - y1 * y1;
		if ( t1 < 0 ) n1 = 0.0;
		else {

			t1 *= t1;
			n1 = t1 * t1 * this._dot( this.grad3[ gi1 ], x1, y1 );

		}

		let t2 = 0.5 - x2 * x2 - y2 * y2;
		if ( t2 < 0 ) n2 = 0.0;
		else {

			t2 *= t2;
			n2 = t2 * t2 * this._dot( this.grad3[ gi2 ], x2, y2 );

		}

		// Add contributions from each corner to get the final noise value.
		// The result is scaled to return values in the interval [-1,1].
		return 70.0 * ( n0 + n1 + n2 );

	}
A 2D simplex noise method.

@param {number} xin - The x coordinate.
@param {number} yin - The y coordinate.
@return {number} The noise value.