skAnchored (shader module)

Stable noise that stays on things, for styleKit blocks. Include after skCommon and skPatterns.

• sk_anchored_fbm(uv, perMetre, octaves): fractal noise laid on the world position of the surface under the pixel from three sides (no seam where a surface turns; the sky by view direction). Sized in metres: a wash's grading, wet patches.
• sk_anchored_cells(uv, perMetre): one random value per patch (blooms, pools, dry patches).
• sk_scaled_fbm(uv, refPx, octaves): noise that stays on the surface and keeps marks about refPx reference pixels across at any distance, by blending two octaves by distance (marks grow into the next octave rather than sliding). Paper tooth, grain, flecks and strokes that should keep their size in the picture.
• sk_scaled_level(uv, refPx), sk_surface_plane(uv), sk_ref_metres(uv): the parts, for drawing your own pattern (cells, strokes) the same way.

For things that move, use skp_triplanar_fbm on the object's own position inside a material (local_position).