c64engine

A game engine for the c64.

Building

Dependencies:

• acme
• cc65

The following dependencies are automatically dealt with by the Makefile:

• Krill's loader
• exomizer (using Krill's intree sources)
• tinycrunch (using Krill's intree sources)

cp config.default.template config.default
vim config.default # edit
make

Running

Before running in VICE, make sure True drive emulation is enabled and IEC-device is disabled.

make run

Use joystick in port 2 to run the demo.

Features

• Bitmap scrolling using AGSP

  This technique only requires 36 raster lines CPU time and 33 raster lines of screen space. All other screen space - including screen memory (used for colors %01 and %10) and color ram (color %11) is moved around as well.

• Sprite-Multiplexer

  Multiplixing 24 x 2 sprites. This means 24 virtual multi-color sprites where each sprite is overlayed with a single-color sprite for more colors and better resolution.

• Tile-Copying

  The binary format of the files is as follows:

  • map.bin: map width * map height bytes (here 256 * 96).

    Each byte is a tile index into the tile data: pixels, screen, colors

  • pixels.bin: tile width * tile height * 8 bytes per tile (here 3 * 2 * 8).

    Each bit pair in a byte is a color number: 0-3 (multicolor)

  • screen.bin: tile width * tile height bytes per tile.

    For each byte, the upper 4 bits are color 1 and the lower 4 bits are color 2

  • colors.bin: tile width * tile height bytes per tile.

    For each byte, the upper 4 bits are ignored and the lower 4 bits are color 3

  Color %00 (the shared background color) is black, but this can of course be changed to any of the 16 colors. If you are generating your own tile data, it is adviced to give priority to color number %11. In this way it is possible to reduce the problem of the sprite pointers overwriting the screen colors if certain tiles use only color %00 & color %11.

• Map-loader (credits for the disk loader go to Krill)

Useful Links

• Spritemate
• Secret colours of the Commodore 64
• Commodore VIC-II Color Analysis
• Commodore 64 memory map