Renderers

About Renderers

Artifacts are stored as submitted by the user using SSTORE2.

When users call the uri() method, the token checks for its registered renderer contract and hands off rendering of the metadata to the specific token renderer.

/// @notice Get the metadata for a given token id.
function uri(uint tokenId) external override view returns (string memory) {
    if (tokenId > latestTokenId) revert NonExistentToken();

    Token memory token = tokens[tokenId];

    return IRenderer(renderers[token.renderer]).uri(tokenId, token, artifact(tokenId));
}

/// @notice Read an artifact.
function artifact (uint tokenId) public view returns (bytes memory content) {
    Token memory token = tokens[tokenId];

    for (uint8 i = 0; i < token.artifact.length; i++) {
        content = abi.encodePacked(content, SSTORE2.read(token.artifact[i]));
    }
}

All renderers have to implement the simple IRenderer interface. They receive the tokenId, the token metadata (name, description, ...) and the resolved artifact data.

IRenderer.sol

interface IRenderer {

    function uri (
        uint tokenId,
        Token calldata token,
        bytes memory artifact
    ) external view returns (string memory)

}

Token.sol

struct Token {
    string  name;            // token name
    string  description;    // token description
    address[] artifact;    // artifact pointers (image/artwork) data
    uint32  renderer;     // index of renderer contract address
    uint32  mintedBlock; // delta init <> created block
    uint64  closeAt;    // timestamp of mint completion
    uint128 data;      // optional data for renderers
}

How renderers generate the metadata is entirely up to them.

Default Renderer

The base renderer implementation that ships with every Mint contract by default simply returns artifact data as a blob.

contract Renderer is IRenderer {

    function uri (uint tokenId, Token calldata token, bytes memory artifact) external pure returns (string memory) {
        bytes memory dataURI = abi.encodePacked(
            '{',
                '"id": "', Strings.toString(tokenId), '",',
                '"name": "', token.name, '",',
                '"description": "', token.description, '",',
                '"image": "', artifact, '"',
            '}'
        );

        return string(
            abi.encodePacked(
                "data:application/json;base64,",
                Base64.encode(dataURI)
            )
        );
    }

}

Renderer Extensions

P5 Renderer

As an initial extension example, we have built a renderer for generating p5.js based artifacts onchain.

Check out the P5Renderer.sol on Github.

This renderer also comes with its custom UI implementation to edit and preview the P5 script.

How this works under the hood is that we encode both the static asset and the script content within the artifact bytecode, and decode it into its parts during rendering.

Also note how the renderer exposes both a script_url with just the artists' p5 script and the complete animation_url with the entire encoded html page.

/// @notice Generate the JSON medata for a given token.
///         We expect the static preview image and P5 script
//          to both be encoded in the artifact data.
function uri (
    uint tokenId,
    Token calldata token,
    bytes memory artifact
) external view returns (string memory) {
    (string memory image, string memory script) = abi.decode(artifact, (string, string));

    bytes memory dataURI = abi.encodePacked(
        '{',
            '"id": "', Strings.toString(tokenId), '",',
            '"name": "', token.name, '",',
            '"description": "', token.description, '",',
            '"image": "', image, '",',
            '"script_url": "data:text/javascript;base64,', Base64.encode(bytes(script)), '",',
            '"animation_url": "', generateHtml(token.name, script), '"',
        '}'
    );

    return string(
        abi.encodePacked(
            "data:application/json;base64,",
            Base64.encode(dataURI)
        )
    );
}

Community Renderers

Developers are invited to get creative and contribute their own to the ecosystem.