references/primitive-sketchy.md

# Sketchy Filter (hand-drawn variant)

Optional displacement filter that wobbles every stroke and edge slightly — turns any minimal variant into a hand-drawn "editorial" register without changing layout. Use when the diagram accompanies an essay rather than technical docs.

## Grammar

```svg

<defs>

<filter id="sketchy" x="-2%" y="-2%" width="104%" height="104%">

<feTurbulence type="fractalNoise" baseFrequency="0.02" numOctaves="2" seed="4"/>

<feDisplacementMap in="SourceGraphic" scale="1.5"/>

</filter>

</defs>

<!-- Apply to a group wrapping shapes — NOT text -->

<g filter="url(#sketchy)">

<!-- rects, paths, circles, lines go here -->

</g>

<!-- Text sits OUTSIDE the filtered group — legibility stays crisp -->

<text ...>Labels go here</text>

```

## Tuning

| Parameter | Range | Effect |

|---|---|---|

| `baseFrequency` | 0.01–0.04 | Lower = lazy wavy lines; higher = jittery. 0.02 default. |

| `numOctaves` | 1–3 | More = more noise detail. 2 is plenty. |

| `scale` | 1–6 | 1 barely-there, 1.5 default, 2 visible, 4+ cartoon. |

| `seed` | integer | Swap for a different random pattern. |

## Critical rule

Filter shapes, NOT text. Displacement-mapped text becomes illegible. Structure your SVG so text is in a sibling group outside the filtered group.

## When to use

- Essay / blog post / newsletter where the diagram is the hero of a narrative page.

- "Working sketch" register — showing something is mid-thought, not final architecture.

## When not to use

- Technical documentation (precision matters).

- Diagrams with dense labels or tight alignments (filter reads as noise).

- Dark variants — wobble reads as artifact on dark backgrounds. Test first.