# Art Blocks Features Script

A guide on how to structure the features script for your Art Blocks project.

# Features Overview

All feature attributes that you want displayed should be directly generated from the transaction hash and should not depend on any other randomness.

This function should essentially encapsulate the feature-determining logic within rendering script but without any library dependencies (e.g. p5js) present (the server won't have access to them).

The function should assume that it receives the tokenData object as an input (containing both a tokenId and hash string), and should use these to return the correct desired feature metadata for a given mint.

Properly displaying your project features requires both a a) feature calculation script and b) setting the feature fields for your project in the Art Blocks website's artist interface.

Updating the features script or features fields for a given project will recalculate features for all tokens within that project.

# Features Script Interface

Important Note: All code required for calculating your features (including any necessary helper functions) must be defined and implemented within the single top-level calculateFeatures function.

 * Calculate features for the given token data.
 * @param {Object} tokenData
 * @param {string} tokenData.tokenId - Unique identifier of the token on its contract.
 * @param {string} tokenData.hash - Unique hash generated upon minting the token.
function calculateFeatures(tokenData) {
   * Implement me. This function should return a set of features in the format of key-value pair notation.
   * For example, this should return `{"Palette": "Rosy", "Scale": "Big", "Tilt": 72}` if the desired features for a mint were:
   * - Palette: Rosy
   * - Scale: Big
   * - Tilt: 72
  return {}

For many artists, the process for writing your features script will likely entail starting with your project script, copying it into the calculateFeatures interface/shell above, and then trimming it down to remove all library (e.g. p5js) references and draw functionality and instead to build the relative key-value object map for your features.

# Features Fields

In order for filtering and rarity (% occurrence of different features) to be accessible via the Art Blocks website, the feature fields must be added in the artist interface UI on the Art Blocks website.

There are three types of feature fields: enum, number, and boolean:

  • For enum fields, values should be outputted as strings in your features scripts.
  • For number fields, the step size set in the feature fields is used for the step size of the slider in the filters. This step size is set in the feature fields UI, not in the script, and should be on a per field basis.
  • For boolean fields, the only values are true and false, so you just need to give the field a name.
  • If there are only a few specific number values expected to be output, an artist might want to use an enum field and output the enumerated possible numeric values as strings (e.g. if the slider UI would not be the best way to navigate these features).

# Migration From Legacy Features Arrays

Previously the features for a given project were defined in a less structured way, via a script that could set a given array of features (e.g. ["Palette: Rosy", "Scale: Big", "Tilt: 72"]) to a globally available features array.

This process is being standardized for the Art Blocks V2 website and token API, which may require some involvement from artists to migrate old projects in alignment with their desires.

To simplify this process, Rev Dan Catt has provided an amazing tool to generate a features script with the new format based on the features of existing projects, which you can find at https://rarity.guide/project/{ProjectNumber}/featurescript (where {ProjectNumber} is swapped out with your project of interest).

This tool is being used to assist the Art Blocks team in attempting to automatically migrate projects, but if you are an artist with an existing project that needs to or would like to modify the output of this automated result, Rev Dan's script is a great starting place.

# Additional Notes

For future projects (that have not yet minted out, which is necessary for Rev Dan's automated migration approach), it is necessary that this data be determined based on the tokenData itself rather than just mapping the tokenId to a given existing set of features as the features cannot be known until time of mint (unless all named features are purely based on the tokenId and not the hash).

You also have the option to upload a json file to set all of your feature fields. The shape of the file should be in the following format:

    "type": "enum",
    "name": string,
    "options": string[]
    "type": "boolean",
    "name": string
    "type": "number",
    "name": string,
    "min": number,
    "max": number,
    "step": number > 0

On upload of the json file it will overrwrite any existing feature fields in the current form. You also are able to download your existing feature fields as a json file using the buttons found in the feature fields form.