For this project I implemented a non-fungible token (NFT) contract where the image generation happened fully on-chain. This was relatively novel at the time where most NFT contracts stored their images off-chain. The images were built as SVGs using basic tags like path, circle, ellipse, and group.

A set of traits (SVG components) and palettes (color schemes) were run-length encoded as bytes and loaded into the smart contract ahead of time. Users could construct their image by selecting traits and palettes on a web-app. This generated a seed which was structured as follows:

    struct Seed {
        uint8 background;
        uint8 backgroundSubPalette;
        uint8 space;
        uint8 spaceSubPalette;
        bool skyEnabled;
        uint8 sky;
        uint8 skySubPalette;
        uint8 land;
        uint8 landSubPalette;
        bool structureEnabled;
        uint8 structure;
        uint8 structureSubPalette;
        bool characterEnabled;
        uint8 character;
        uint8 characterSubPalette;
    }

This seed was passed to the contract and associated with the minted token. Users only incurred the cost of storing the seed state. The SVG metadata was decoded and generated directly on-chain from the seed via a view function, making it free.