TRANSPARENCY

Nebula can change the sprite drawing method, to make them partially transparent, this is a
visual improvement, not a hardware feature.

In the current version, only video cards using 565 16 bit mode are supported (most cards use this mode). I’ll add
support for 555 cards (old video cards) in next releases. If you get strange colours when transparency is enabled,
then your video card is a 555 one.

To do so, it needs some external data tables that tell it which sprites have to be drawn
transparent and which level of transparency it should use.

The tables are .bld files stored in the CONFIG folder. You can have more than one table for each game
and select which one you want to use from the in-game menus (ESC key), you can also disable transparency
selecting the None table in the list.



To make such tables you have 2 options:
	- Manually edit the table (see below for info about the file format), that is quite hard.
	- Use the tileviewer. To access the tileviewer, pause the game and press the keys A and L
	at the same time, you’ll see all the sprite tiles for the game. The numbers to the right are
	the current tile code, the current palette and the 5 palette slots (CPS only)
           The keys to browse the table are:
		Up,Down,Left,Right: move the selection 1 tile to the specified direction
		PgUp,PgDown: move the selection a page of tiles.
		Numpad +,-: move the selection +-0x8000 tiles
		Left Shift: extend selection
		Numpad /,*: cycle the palette value
		1: make the tile 25% transparent
		2: make the tile 50% transparent
		0: make the tile opaque
		3,4,5,6,7: assign the current palette to the slot (3=1st slot, 4=2nd...) The tile will
		be drawn in the selected way (transparency) only if the palette matches any of
		the values on the slots, if not, the opposite value will be used (opaque<->25% trans)
		W: save the table to disk (the name is the rom name .bld)

	The current selected tile has a white square. 25% transparent tiles have a blue one, and 50% have
	a green border.


The file format is:

; anything after a ; is a comment
Name <Game Name>
Game <Game romset>

<codes> <transparency value>

<codes> can specify a single code or a range
<transparency value>: 	1: 25% Transparent, 2: 50% Transparent, 3: Opaque

Ex:

; Sprite transparency data for Street Fighter Alpha/Zero
Game sfa
Name SFA Table by Razoola

; These clear all character shadows
1B7A4 2
1B7AD-1B7AF 2
