This is a simple engine that allows to make "pseudo-3D" games for Nintendo Game Boy using GBDK-2020.
You need the latest version of GBDK-2020 (4.1.1 for now) to compile this example. I'm also using the tool from ZGB engine to convert the "Gameboy Tile Designer" tiles into the source file and a tool to convert the description of the scene into the source file (tool source is included).
The global world map consists of "rooms". Each room has a 9x9x4 cell 3d-map: four 9x9 2d layers. The rooms and the "world map" are defined in the rooms.3dmap file, which is a text file with "ini-file" format. Comments in that file describe it's internal structure. This file is converted into the source file by the "mapcvt" utility at compile-time. Rooms and global world are translated into the C linked-list structures. That allows to save a lot of space and accelerate the drawing functions. Collision map for the current room is restored into ram from that lists when the room is changed. Maximum number of items in the room is 254.
Each room item consist of two 16x16 pixel "sprites", the first one is the item itself, and the second one is a bit mask, which defines what pixels are transparent. When the item is drawn, the part of the background is AND'ed with the mask, and then OR'ed with the sprite. The graphics is in GBTD format (file: scene_resources.b1.gbr), and is converted into the source file at compile time by the "gbr2c" utility.
Tony.