Text Rain (Utterback & Achituv)

Math essence

Let S : [0,1]² → [0,1] be the silhouette image. The 2D optical flow field is f = (∇ₓ S, ∇ᵧ S). On a coarse cells×cells lattice each character c at (i, j) advances by (Δi, Δj) = (g + f_x(i,j)·strength + ε_x, v_flow_y(i,j)·strength + ε_y). When the local S exceeds a threshold, the character settles in that cell. The cells form a hard-occupancy grid, so no two characters can share a cell. The piece reads as a Poisson-disc-like fall: characters never stop in mid-air, and they pile up only on the silhouette.

Parameters

Reference

First 60 lines of reference.py. Full source: library_external/generative_pioneers_2/utterback_text_rain/reference.py

from __future__ import annotations

from typing import ClassVar

import imageio.v2 as imageio
import numpy as np


class UtterbackTextRain:
    family: ClassVar[str] = "generative_pioneers_2"
    sketch: ClassVar[str] = "utterback_text_rain"

    POEM_LINES = (
        "TALK YOU AND I",
        "EVERY WALK IS A TALK",
        "EVERY BODY MAKES A SOUND",
        "EVERY WALK A BODY TALKS",
        "I HEAR YOUR BODY TALK",
        "BODIES HEAR BODIES",
    )

    PALETTE = (
        (220, 60, 60),
        (240, 200, 60),
        (60, 140, 230),
        (90, 220, 130),
        (220, 110, 220),
        (240, 140, 80),
    )

    def __init__(
        self,
        dim: int = 512,
        cell: int = 14,
        gravity: float = 0.6,
        obstacle_bias: float = 0.55,
        flow_strength: float = 0.5,
        silhouette_threshold: float = 0.4,
        silhouette_seed: int = 99,
        font_size: int = 13,
        bg_color: tuple[int, int, int] = (245, 245, 240),
        seed: int | None = None,
    ) -> None:
        self.dim = dim
        self.cell = cell
        self.gravity = gravity
        self.obstacle_bias = obstacle_bias
        self.flow_strength = flow_strength
        self.silhouette_threshold = silhouette_threshold
        self._silhouette_seed = silhouette_seed
        self.font_size = font_size
        self.bg_color = np.array(bg_color, dtype=np.uint8)
        self._seed = seed
        self.rng = np.random.default_rng(seed)
        self.canvas = np.full((dim, dim, 3), self.bg_color, dtype=np.uint8)
        self._silhouette = self._build_silhouette()
        self._flow = self._build_flow()
        self._chars: list[dict] = []
        self._init_chars()
        self.time = 0