leonardo — his hand, his page, his materials

Not "Renaissance sketch style." Leonardo's sheets have a specific material language and a specific page logic, both measured here off fifteen real drawings listed in sheets/CREDITS.md (where each one is and what was read off it). Run python3 scripts/fetch_sheets.py once to download them from Wikimedia Commons; they are the style anchors plate.py attaches.

Always label the output as made in his manner, never as his. Don't use his name to sell something in customer-facing copy.

What his sheets actually are (the measured language)

Read off the sheets. Every STEM in prompts/ is a paraphrase of this list.

• The page is a working page, never a picture. Several studies of one thing at different scales share a sheet: a main study, sections and cutaways, a detail, a tiny diagram lettered a b c, an abandoned first attempt left faint. Nothing is centred. Text wraps around the drawings, some lines with a thin leader pointing in (fetus sheet, shoulder sheet).
• Left-handed hatching. Shadow is parallel strokes running upper-left → lower-right (\\), close-set, curving with the form, denser where the form turns from the light. He hatches the ground behind a form to push it forward (skull, Vitruvian's legs). Cross-hatching is rare.
• Sections and transparency. A skull sawn in half; a womb opened like a fruit; a machine drawn with its casing gone. His way of explaining a thing is to cut it.
• Motion as hair. Water, cloud, smoke, wind are nested spirals of dozens of fine parallel arcs (the Deluge). Hair and beard are long rhythmic waves (Turin self-portrait).
• Six material modes, and they don't mix on one sheet:

  mode	what it is	the anchor sheets
  ink	pen + brown iron-gall ink over faint black chalk, brown wash in the deep shadow; the anatomy and machine sheets	shoulder, fetus, flying machine
  codex	a notebook folio that is mostly writing, with diagrams sitting in the text	Arundel opening, Atlanticus 307v, Vitruvian
  chalk	red chalk (sanguine), one pigment, sfumato modelling	Turin self-portrait, grotesque heads
  silverpoint	metalpoint on a coloured prepared ground (blue-grey or pink-buff), lead-white heightening	woman's hands, horses
  linen	brush + grey tempera on prepared linen, pure tone, no line	seated drapery
  deluge	pen + ink + wash storm/landscape, vortices and hooked strokes	Deluge, 1473 Tuscan landscape

• The paper is a character. Cream-to-buff laid paper aged to ochre at the edges, foxing, brown stains, a torn corner, show-through from the verso. The real sheets also carry a crowned-ER collector's stamp and inventory numbers — those are the museum's, not his; never ask for them and probe every plate for an invented one (the engine has forged a real artist's signature unasked; see make-art).
• Mirror script. Small, even, right-to-left, same ink as the drawing, in blocks. On the working pages (ink, codex) it's most of the surface. The chalk, metalpoint and linen studies mostly have no writing at all — don't add it where he didn't.

Step 1 — decide the mode and the aspect before writing a word

The mode is the whole look, so it's the first decision, and it's usually forced by the brief: a mechanism or an anatomy → ink; a page of reasoning with a big diagram → codex; a portrait, a tree, a face → chalk; hands, animals, anything about touch and light → silverpoint; cloth → linen; weather, water, a valley → deluge.

Aspect: 3:4 is a folio and the default; 4:3 for a landscape sheet; codex sheets are always 3:4. He never drew a 16:9.

Ask one question if the brief is a subject and nothing else: working page or finished study? It sets mode (ink/codex vs the rest), writing (on vs off) and how many studies share the sheet. Everything else — aspect, anchors, size — is mine to decide.

Step 2 — write the SUBJECT as studies, not as a picture

The prompt is STEM (fixed per mode) + SUBJECT (the only variable) + NOTES (per mode) + TAIL (fixed). scripts/plate.py assembles it and attaches the mode's anchor sheets:

python3 scripts/plate.py --mode ink --aspect 3:4 --size 2K \
  --out art/<slug>/candidates/r1/1-<name>.png \
  --subject "A study sheet dissecting …: one large main study …; beside it three smaller
             studies — …; a tiny diagram in the corner showing …, points lettered a, b, c."
python3 …/plate.py --list-modes          # modes, their default writing, their anchors
python3 …/plate.py … --dry-run           # print the assembled prompt, spend nothing

The SUBJECT that works is a list of studies on one sheet, each with its scale and view: "one large main study of X seen three-quarters from above with Y cut open; beside it three smaller studies — A alone, B in section, C seen from below; a tiny diagram in the corner showing Z, points lettered a, b, c." Write a picture ("an espresso machine on a table") and you get an illustration on old paper, which is the standard failure.

Draft at 2K (~$0.13); spend 4K only on the pick. The engine needs network access (make-art).

Step 3 — read the plate against the sheets, then fix the prompt, not the plate

Look at every plate at full size beside its anchor sheet. The three things that actually go wrong, in order of how often:

1. The writing leak. Told to write "Renaissance Italian mirror handwriting", the engine wrote "Reall bennifsance Italian mirror Italian mirror right to left" — my instruction, mirrored, along the bottom of an otherwise perfect silverpoint sheet. Told the notes were about a piston, it wrote "Piston seal" and "Mechanical advantage" in plain English. Never describe the writing in words it can copy, and never let the SUBJECT's nouns sit near a caption slot. prompts/notes-*.txt now says the hand is illegible by design and forms no word in any language; that cut the leak from a whole sentence to two or three half-English labels per ink sheet, and to zero on none. So: modes without writing default to none; an ink/codex sheet with margin notes needs a read for leaked English and a re-roll (or a crop) if a word survives. Leaks land next to the small studies — check there first.
2. Right-handed hatching. The engine hatches / about as often as \\, whatever the STEM says. When the sheet has no legible writing, --flip mirrors it horizontally and the hatching becomes his; check that the composition survives being reversed (a lettered diagram will not — its letters flip). Don't fight this in the prompt; it doesn't listen.
3. Cartoon foliage. First red-chalk birches came back as scalloped cloud-lobes. The chalk STEM now says foliage is a mass of tone built from short flicked strokes, never outlined lobes, and the SUBJECT should say "the leaf-masses as soft tone" rather than naming leaves. Same rule generalises: name the tone you want, not the object the engine has a cliché for.

Then the standard make-art probes: edges (these plates are meant to show the sheet's own torn edges against nothing — that is the design, not a border to trim), and corners for an invented stamp or signature.

Step 4 — land it

A folder art/<slug>/ with a README, finals numbered by rank, candidates/, prompts/. plate.py writes <out>.prompt.txt beside every plate, so the prompts folder is free.

Reading him (the other half of the persona)

His notebooks are public domain in J.P. Richter's 1883 arrangement (The Notebooks of Leonardo da Vinci, free on Project Gutenberg), in twenty-two books by subject. When the job is what did he think — about shadow, trees, water, how to study, the grotesque, flight — read the book, quote the paragraph number, and don't improvise. The lines that bear directly on drawing, attested in the book on the practice of painting (Richter paragraph numbers):

• 522. "When you draw take care to set up a principal line which you must observe all throughout the object you are drawing; every thing should bear relation to the direction of this principal line." — the one rule for a SUBJECT paragraph too.
• 502. A master who trusts memory over drawing from nature is "graced with extreme ignorance, inasmuch as these effects are infinite." — why the sheets are studies, plural.
• 523. The glass-pane method: draw on glass with "a brush or red chalk", trace to paper, "afterwards transfer it onto good paper" — his own account of the transfer chain that ends in pouncing (628, the panel recipe: "Then pounce and outline your drawing finely").
• 540. "When you draw from nature stand at a distance of 3 times the height of the object."
• 529. "How the mirror is the master [and guide] of painters" — check a drawing against the mirror image of the thing. The reason --flip is a legitimate move and not a cheat.

A famous line that isn't in the notebooks isn't his until you find it there. His voice when not instructing — the fables, the prophecies, the letters asking to be paid — is in books 19–21 and is drier and funnier than the reputation.

References

• Engine, flags, the paste-to-disk trick, the border probe: make-art. Method for a spread off one reference: image-riff. This skill is a third layer: a fixed language with modes instead of a language read off a pasted image.
• sheets/CREDITS.md — provenance of the fifteen anchors (all public domain, Wikimedia Commons); sheets/meta.json is the raw Commons record used by fetch_sheets.py.