Godotboy

A monochromatic posterisation shader with a customisable palette.

About

A while back I was participating in the yearly GBJAM, which requires entrants to make a game either for or with the same limitations as the Nintendo Game Boy:

• A virtual resolution of 160x144
• A palette of 4 distinct colours

While it would be simple enough to just draw the graphics using 4 colours and call it a day, I wanted more flexibility. So I started work on a shader solution.

Usage

The repo contains a demo project that indicates how the shader ought to be used. This demo project also makes a great start for any GBJam submissions written using the Godot engine, since all of the project and import options have been preconfigured.

In general, the shader should be applied as a material to a ColorRect node placed above all objects in the scene, which can be achieved by making it the child of a CanvasLayer. Then a palette texture needs to be set, which can be done through the editor.

If you want to change the default palette at runtime, you can do so by accessing the shader params of the node that has the associated shader material through a suitable script.

For best results, all art assets should be in greyscale with evenly spaced red, green and blue values. This will ensure a more accurate conversion to the chosen palette.

This shader is intended for 2D games using low resolution pixel art graphics, but is helpful in making 3D games also.

Features

• Support for up to 256 distinct colours
• Full posterisation step to allow for conversion of non-pixel-art textures
• Automatic greyscale conversion using the luminosity method

License

See LICENSE for more details.