The words we use
A plain-language glossary of the ideas behind consistent AI picture books — the Character Sheet, the Consistency Engine, drift and more.
- Character Sheet
- A locked description of a book’s hero — a written profile plus approved reference images — that every page is generated against so the character stays consistent.
Image models don’t remember what they drew a moment ago, so Once Books re-supplies the Character Sheet on every single page. It is the single source of truth for who the hero is, and the reason a book looks like one book instead of a set of related pictures.
- Consistency Engine
- The system that keeps one child recognisable across a whole book: locked character descriptions, reference-image conditioning, a frozen art style, and deterministic seeds.
“Consistency Engine” is our name for the whole approach, not a single feature. It exists because statelessness — the model forgetting page to page — is the core reason most AI picture books drift.
- Deterministic Seed
- A fixed starting value for generation, so the same inputs produce the same result — which is what makes a page reproducible and regeneration predictable rather than a fresh roll of the dice.
Image models start from a random seed; change nothing but the seed and you get a different picture. Controlling it is one of the quieter locks in the Consistency Engine: it turns “generate again and hope” into a repeatable step you can trust months later.
- Drift
- The gradual loss of consistency across an AI-generated book — the hero’s face, proportions or style changing page to page — which Once Books is built to prevent.
Drift is the failure mode of naive AI books. Because each page is a fresh guess, the child from page one slowly becomes someone else. Locking the character and style is what stops it.
- Environment Sheet
- Locked descriptors for a recurring setting — a bedroom, a wood, a classroom — so a place looks like the same place each time the story returns to it.
Characters aren’t the only thing that drifts. Without a fixed environment, page three’s forest is a different forest by page nine. The Environment Sheet applies the same locking idea to places that the Character Sheet applies to people.
- Identity Sheet
- A character rendered once in canonical poses — front, three-quarter, profile and full-body — that becomes the fixed reference set every later page is generated against.
Where the Character Sheet is the written description, the Identity Sheet is the visual anchor: the same face and build seen from several angles, so the illustrator has enough to keep the likeness steady no matter what the character is doing on a given page.
- Reference Image
- One of the approved photos or renders that anchors a character’s appearance, supplied to the illustrator on every page rather than relied on from memory.
Your uploaded photos become reference images. A few clear ones from a mix of angles give the illustrator enough to keep the likeness steady across the whole book.
- Style Profile
- The single art style chosen once and frozen onto an entire book, so every page inherits the same look instead of being re-invented.
The style profile is why page one and page sixteen belong to the same illustrator. It is chosen before generation and applied uniformly, so there is no jarring switch from watercolour to a 3D render halfway through the story.