map( functionToMap, context ) {

		const length = this.data.length;
		context = context || this;

		for ( let i = 0; i < length; i ++ ) {

			this.data[ i ] = functionToMap.call( context, this.data[ i ], i, this.data );

		}

		return this;

	}
Apply a function to all the voxels, be careful, the value will be replaced.

@param {Function} functionToMap A function to apply to every voxel, will be called with the following parameters:
value of the voxel, index of the voxel, the data (TypedArray).
@param {Object} context - You can specify a context in which call the function, default if this Volume.
@returns {Volume} A reference to this instance.