Koi Carp Generator

A Blender add-on that generates fully procedural Japanese koi carp (nishikigoi): body shape, overlapping scales, the patterns of the major varieties, translucent fins, eyes, barbels and an animated swim rig. Pick a variety and a seed, click Generate Koi: every fish is unique, and one button fills a whole pond.

The anatomy is matched to photographs of real carp: a broad head with full cheeks, a protractile mouth with rounded lips, gill covers that open onto the gill arches, eyes built as real geometry with a refracting cornea, barbels welded to the lip. In profile, the average koi's silhouette overlaps the reference model's by 95%. Fins grow out of the body from a fleshy root and have real thickness: rays that branch towards the edge, a thin membrane that lets backlight through.

24 varieties, from Kohaku to Kumonryu, with the details judges look at: the Kohaku's steps, the Sanke's kata-sumi, the Showa's menware, the Asagi's blue netting. The back edge of a red patch follows the scale outlines (kiwa), the front edge shows through pink under the white scales (sashi). A Fragmentation setting goes from a show koi's clean patches to the broken patterns of a pond koi.

Built for production: a single closed, manifold quad cage shared by every koi (same vertices, same UVs), a 0-1 UV atlas, a full PBR map set (colour, normal, ORM, height, pattern masks) that works in Cycles and EEVEE, and a bake to the atlas for real-time or to six UDIM tiles for film. Butterfly, doitsu, gin rin and hikari options, and a one-click lighting studio around the selected koi.

The project moves forward version by version, 31 so far, each one focused on a single point (silhouette, mouth, eye, scales, skin) and compared against reference photos. Every step is checked by an automated test suite that runs inside Blender. Below, version 1.0 and version 1.31, in the same composition.