swapping 3D engine

3D engine implements visibility distance, far away objects will be swapped into hard disk to increase framerate and reduce memory usage. Visibility distance adjusts automatically. This techniqe allows handling of a very complex world (for QBasic). World is broked down to 100x100x100 units sized blocks, and stored on disk into separate files. One file per block. This is just an experiment to test out the idea, world will be synthezied and constantly updated. Engine allows user to freely fly around using mouse and keyboard.

System requirements:
	CPU 500 MHz or better
	MS QBasic (preferably QB 4.5) in your path