todo

一段linux下用OpenGL实现的小程序

For future versions...
----------------------

* Improved edge handling
	As you'll realize if you try to create some real
	game levels with this engine, getting the tile
	edges right at all times is rather cumbersome.
	It's also rather inefficient with all the "dummy"
	tiles you need to get "border pixels" in the
	right places.

	A simple improvement would be to add a border of
	one pixel around each tile (either shrinking the
	tiles to 30x30, or adding space in the palette,
	making them 34x34 total), and have the artist
	explicitly draw the border pixels for each tile.
	This avoids the dummy tiles.

	The next step would be automating the generation
	of border pixels. The engine would have to look
	at the map to find all combinations. Well designed
	maps with only "natural" combinations of tiles
	should generate few, if any extra tiles - the
	engine would basically just fill in the border
	pixels.

* Parallax scrolling
	Nothing much to this at all; the only thing to
	keep in mind is that RGBA textures must be used
	for any tiles bordering to transparent areas in
	the overlay layers. (Otherwise the edges will
	flicker!) This does not, however, mean that *all*
	tiles used in overlay layers must be RGBA! Tiles
	that are entirely surrounded by opaque pixels
	may of course be totally opaque without causing
	trouble.

* Alternative method
	Instead of rendering the static tile images
	directly, one could make use of an array of
	procedural textures, acting as a tiled frame
	buffer. These tiles would be rather large, and
	updated part by part, as needed when the screen
	is scrolled. Tiles that are scrolled off the
	edges are recycled.

	There are two obvious advantages with this method:

		1) Border pixels can be generated directly
		   from the map very easily.

		2) It's easy to implement advanced
		   software rendering on top of this.

	One minor problem as well; this method can't
	really take advantage of the fact that many tiles
	in parallax scrolling layers can be RGB rather
	than RGBA, as noted under "Parallax scrolling".