Halftone lines shader

[uuuulala]

Note

Low Risk
Additive shader and docs only; no changes to shared runtime paths beyond new exports, matching existing halftone filter patterns.

Overview
Adds a new Halftone lines image filter that renders photos as line-based halftone patterns, with stroke thickness and grid warping driven by image luminance.

The core ships in @paper-design/shaders as halftoneLinesFragmentShader plus param/uniform types and seven grid modes (lines, waves, radial, truchet, etc.), stroke/color/grain controls, and optional original-image coloring. @paper-design/shaders-react exposes HalftoneLines, halftoneLinesPresets (six presets), and public exports from both packages.

Docs follow the existing shader playbook: Leva playground at /halftone-lines (sample image cycling, upload, URL params), halftoneLinesDef for API docs, a shadcn registry example component, and registry.json registration.

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[cursor]

Presets use contain not cover

Medium Severity

All halftoneLinesPresets spread defaultObjectSizing without overriding fit, so they keep contain. Sibling image filters (halftone-dots, halftone-cmyk, fluted-glass) set fit: 'cover', so the default and preset demos letterbox the source image instead of filling the canvas like the other filters.

Additional Locations (2)

• packages/shaders-react/src/shaders/halftone-lines.tsx#L48-L78
• packages/shaders-react/src/shaders/halftone-lines.tsx#L79-L109

 

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[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

There are 5 total unresolved issues (including 3 from previous reviews).

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^{Reviewed by Cursor Bugbot for commit 903487f. Configure here.}

[cursor]

Contouring smoothstep args inverted

High Severity

smoothstep(length(uv), 0., 1.) passes edge0 >= edge1 for nearly every fragment, which is undefined in GLSL ES 3.00. That value feeds contouring.y and thus grid rotation whenever gridContouring is non-zero, so contouring rotation becomes driver-dependent instead of a defined falloff.

 

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[cursor]

Stroke invert flips palette colors

Medium Severity

toLum always applies u_strokeInverted, and inkMix uses toLum to blend colorMid and colorFront. Enabling strokeInverted therefore swaps the palette assignment, even though docs say inversion only affects stroke width and leaves colors unchanged.

Additional Locations (1)

• packages/shaders/src/shaders/halftone-lines.ts#L296-L314

 

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