The Stencil
The identity engine that layers physarum behind the Shumi mascot in four formation modes.
The Stencil layers the physarum swarm behind and through the Shumi mascot, creating compositions where organic signal networks grow around a centered image. This is the identity engine for Shumi agent avatars.
What It Does
The Stencil runs two simultaneous physarum simulations:
Background network: A full-viewport swarm that fills the canvas behind the mascot
Mascot physarum: A second swarm constrained to the mascot's shape via edge detection and density mapping
The mascot art fades in with a chromatic aberration entrance animation. A ghost afterimage (retinal-burn effect) provides depth, and the mascot "breathes" with a subtle scale pulse.
Formation Modes
The Stencil offers four formation modes, selected via buttons in the top-right corner (or keys 1–4). Each mode changes how the mascot physarum is rendered.
Mode 1: Ramp (Default)
ASCII art rendering. Trail intensity maps to a character ramp (·:;=+*#%@). Low density gets dots, high density gets dense characters. The result pulses with brightness oscillation. This is the default Shumi stencil look.
Mode 2: Code
Similar to Ramp, but uses a code-like character set. Gives the mascot a "source code" or matrix aesthetic.
Mode 3: Mold
Pixel-based rendering instead of ASCII. The mascot physarum renders as smooth colored trails, creating a biological mold appearance. Best for organic, high-fidelity compositions.
Mode 4: Hybrid
Combines ASCII and pixel rendering. Mixes the structured character grid with smooth trail blending for a layered, textured result.
Settings Panel
Click ☰ Settings (top-left) to open the settings panel. The panel slides out from the left edge and contains three sections of controls.
Background Network
Full colony parameters for the viewport-filling background swarm:
Colony
Agent Count (2k–15k), Speed, Sensor Distance, Sensor Angle, Turn Speed, Steps/Frame, Spawn Rate
Chemistry
Deposit, Decay, Diffusion
Appearance
Trail Brightness, Agent Glow, Food Count, Food Strength, Spawn Radius
Mascot Physarum
Colony parameters for the swarm that grows within the mascot shape:
Colony
Agent Count (1k–10k), Speed, Sensor Distance, Sensor Angle, Turn Speed, Steps/Frame, Spawn Rate
Chemistry
Deposit, Decay, Diffusion
Appearance
Trail Brightness, Agent Glow, Spawn Radius
Stencil Controls
Fine-tuning for how the mascot physarum interacts with the image shape:
Master Opacity
Overall stencil visibility (0–1.5). Higher values = more visible mascot trails
Pulse Speed
Speed of the brightness oscillation cycle
Formation Speed
How quickly the stencil pattern forms on load
Edge Strong
Strength of edge detection for sharp boundaries
Edge Weak
Threshold for subtle edge features
Edge Fade Depth
How deep the edge fade extends into the mascot shape
Dark Threshold
Luminance threshold for identifying dark regions (eyes, outlines)
Dark Edge Boost
Brightness multiplier for edges near dark areas
Fill Density
How densely cells are deposited inside the mascot shape
Web Worker Architecture
The Stencil uses a Web Worker (stencil-worker.js) with OffscreenCanvas to run both simulations off the main thread. This keeps the UI responsive and enables smooth 60fps performance even with high agent counts.
If OffscreenCanvas isn't available, it falls back to a legacy single-thread path. Add ?legacy to the URL to force legacy mode.
Spacebar Blast
Press and hold Space (or long-press/touch on mobile) to trigger a blast effect. This temporarily maxes out stencil opacity and trail brightness, creating a high-contrast reveal of the mascot. Release to fade back to normal.
The blast also fires automatically on page load as an entrance effect.
LP Mode
Add ?lp to the URL to enable Landing Page mode. This hides all UI controls (settings, mode buttons, bottom bar, watermark) and positions the mascot higher on the viewport. Designed for embedding as an iframe hero background in landing pages (used by demo.html).
Share URL System
Click Share in the bottom control bar to copy a shareable URL. The URL encodes:
Seed
seed
seed=42069
Formation mode
mode
mode=3
Master opacity
master
master=0.50
Edge strong
es
es=0.35
Edge weak
ew
ew=0.15
The URL updates automatically as you change settings. Recipients see the exact same composition.
Palettes & Textures
The Stencil uses 8 palettes (Ember, Frost, Moss, Pearl, Bloom, Honey, Tide, Rust) and 8 texture profiles (standard, crystalline, smoke, coral, silk, electric, flow, spore). Both are selected deterministically by seed. See Swarm Palettes & Modes for details.
Controls Summary
☰ Settings
Top-left
Open/close settings panel
1 2 3 4
Top-right (or keys)
Switch formation mode
New Seed
Bottom center
Randomize seed and restart
● Record
Bottom center
Start/stop WebM recording
Save PNG
Bottom center
Capture current frame
Share
Bottom center
Copy shareable URL to clipboard
Space
Keyboard
Hold for blast effect
Stencil slider
Bottom (mobile only)
Quick master opacity adjustment
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