Character Consistency Without Training: The “Cast Sheet” Method (Steal It From Runway Gen‑4, Use It in Veo3Gen)

AI video is getting better fast, but one problem keeps resurfacing for solo creators and small teams: you make Clip 1 and love the character… then Clip 2 shows up with a slightly different face, outfit, or “same room” that suddenly isn’t the same room.

As of early 2026, the industry’s focus on consistency is no longer a niche concern—it’s the difference between a one-off experiment and a campaign you can actually ship.

This post borrows a useful framing from Runway Gen‑4’s positioning around consistency and turns it into a tool-agnostic workflow you can apply in Veo3Gen (or any generator): the one-page Cast Sheet.

Why character consistency breaks in AI video (and why prompts alone aren’t enough)

Most people try to solve continuity by writing longer prompts. That can backfire.

Here’s why consistency tends to drift across clips:

• Every new prompt is a new negotiation. If you rewrite the prompt each time, you unintentionally change priorities.
• Too many moving parts. Character + outfit + props + location + camera + style + action + mood is a lot. Small changes can ripple.
• You’re describing instead of anchoring. Adding adjectives often introduces new degrees of freedom.

The fix isn’t “more words.” It’s fewer variables per clip—and a repeatable way to keep the important variables locked.

What Runway Gen‑4 is really promoting: cast, scout, block

Runway’s Gen‑4 research post explicitly emphasizes the ability to generate consistent characters, locations, and objects across scenes (https://runwayml.com/research/introducing-runway-gen-4). It also claims you can set a look and feel and maintain coherent environments while preserving style, mood, and cinematographic elements frame-to-frame (https://runwayml.com/research/introducing-runway-gen-4).

Under the hood, you can think of that message like a film workflow:

• Cast: define who/what must stay the same (character, product hero object)
• Scout: define where it happens (location and lighting)
• Block: define how it moves (camera/lens rules and action constraints)

Runway also highlights combining visual references with instructions to create new images and videos with consistent styles, subjects, and locations—without fine-tuning or additional training (https://runwayml.com/research/introducing-runway-gen-4). Even if your tool of choice is different, that “reference + instruction + repeatable structure” idea is extremely portable.

The Veo3Gen “Cast Sheet”: what it is (1 page) and when to use it

A Cast Sheet is a one-page spec you reuse across multiple clips. It’s not a screenplay. It’s not a mega-prompt. It’s a continuity contract.

Use it when you need:

• Multi-clip ads (same spokesperson, different hooks)
• YouTube Shorts series (same character, new situations)
• Product demos (same product hero, multiple angles)
• Any story sequence where “close enough” isn’t close enough

The key outcome: you stop re-inventing your prompt from scratch, and you start producing variants of the same production.

Build your Cast Sheet in 15 minutes (copy/paste template)

You can do this in a doc, Notion page, or a shared team note. The goal is to make it easy to paste the important pieces into each generation.

Copy/paste Cast Sheet template

Project name:

Character (who):

• Name/role:
• Age range / vibe (avoid overly specific claims):
• Persona keywords (3–6):

Wardrobe (must stay stable):

• Outfit basics:
• Footwear/accessories:

Defining features (identity anchors):

• Hair (length, color, style):
• Face cues (e.g., freckles, jawline, glasses):
• Body silhouette (broad/lean, height impression):

Environment (where):

• Location type:
• Time of day / weather:
• Background landmarks:

Props (what repeats):

• Primary prop(s):
• Secondary prop(s):

Color palette (3–6 colors):

Lighting (keep simple):

• Key light direction:
• Soft vs. hard:
• Practical lights (lamps/neon/etc.):

Lens / camera (continuity rules):

• Focal length vibe (wide/normal/tele):
• Framing defaults (CU/MS/WS):
• Camera height (eye-level/low/high):

Movement rules (blocking & motion limits):

• Subject movement style:
• Camera movement allowed:

Forbidden changes (“don’t change” list):

Prompt ‘anchor’ line (paste into every clip):

How to write a good anchor line (without over-describing)

Your anchor line should be:

• Specific about identity (who/what it is)
• Specific about the stable look (wardrobe + key features)
• Neutral about everything else (don’t lock action, camera, and mood here)

Example structure (generic):

“Same character: [role], [wardrobe], [defining features], in [environment], [lighting], natural cinematic look.”

Then each clip prompt becomes: Anchor line + Clip instruction.

How to use the Cast Sheet in Veo3Gen: 3 repeatable clip patterns

Think in patterns, not one-offs. Your patterns should change one major thing at a time.

Pattern 1: Same character + new action

Use when you’re making a sequence (or multiple ads) featuring the same person.

• Keep: character identity, wardrobe, core lighting, environment
• Change: the action and maybe the framing

Prompt structure:

1. Paste Anchor line
2. Add: “In this clip, the character [does X]…”
3. Add only one camera note (e.g., “medium shot”)

Why it works: you’re not asking the model to re-decide who the character is every time.

Pattern 2: Same location + new blocking

Use when the world is your brand asset (storefront, studio set, kitchen, desk setup).

• Keep: environment description, lighting direction, color palette, props that define the space
• Change: where the character stands/sits and how they move through the space

This echoes Runway’s emphasis on coherent world environments while preserving cinematographic elements (https://runwayml.com/research/introducing-runway-gen-4).

Pattern 3: Same product hero + new angle

Use for product demos and ecommerce creatives.

• Keep: product appearance, materials, brand colors, background set
• Change: angle, shot size, and interaction

Runway notes regenerating elements from multiple perspectives and positions within scenes (https://runwayml.com/research/introducing-runway-gen-4). You can treat that as a creative brief: your product is the “character,” and the cast sheet keeps it on-model across angles.

Continuity guardrails: wardrobe, props, camera rules, and “don’t-change” lists

Continuity is mostly about deciding what is not allowed to change.

The “don’t change” list is your secret weapon

If you only add one thing to your workflow, add this.

Examples:

• “Do not change hairstyle or hair color.”
• “Do not add/remove glasses.”
• “Do not change jacket color or logo placement.”
• “Do not change room layout; keep the same couch and window position.”

Warn against over-describing: stabilize first, stylize later

When continuity fails, the temptation is to add more adjectives:

• “hyper-real, ultra-detailed, cinematic, filmic, 8K…”

That often increases randomness because you’re introducing competing style targets.

Instead:

1. Lock identity + wardrobe + environment
2. Limit action complexity
3. Only then explore stylistic flourishes

First-tweak checklist (when continuity fails)

Use this quick checklist before you rewrite everything:

• Reduce changes per clip (change one major variable, not five)
• Lock wardrobe + key props (repeat exact phrasing)
• Reuse the anchor line verbatim across clips
• Adjust camera/motion before style (simplify movement; pick one shot type)
• Shorten the prompt if you’ve been piling on descriptors

Common failure modes (and what to tweak first)

Failure mode: “Same character, different face”

Tweak order:

1. Strengthen defining features (2–4 clear anchors)
2. Remove competing descriptors (especially style noise)
3. Reassert “same character” + wardrobe in the anchor line

Failure mode: “Wardrobe drift”

Tweak order:

1. Make wardrobe a single, concrete sentence
2. Add it to Forbidden changes
3. Keep accessories minimal (each accessory is another variable)

Failure mode: “Location changes shape”

Tweak order:

1. Add 1–2 landmarks (e.g., “large north-facing window,” “red sofa against brick wall”)
2. Lock lighting direction (e.g., “soft daylight from the left”)
3. Reduce camera movement (fast motion tends to invite reinterpretation)

Mini case study ideas: 3 creator scenarios

1) Performance ads for a small brand

• Cast Sheet: spokesperson + signature outfit + brand color palette
• Pattern: Same character + new action (three different hooks)
• Output: 6–12 clips that feel like one campaign, not six different universes

2) YouTube Shorts character series

• Cast Sheet: character identity + one “home base” location
• Pattern: Same location + new blocking (different positions in the room)
• Output: continuity viewers recognize instantly

3) Product demo pack for a launch week

• Cast Sheet: product hero + tabletop set + lighting recipe
• Pattern: Same product hero + new angle
• Output: consistent visuals across announcement, feature callouts, and retargeting

FAQ

Does this replace model training or fine-tuning?

No—this is a workflow for staying consistent without training. Runway explicitly frames Gen‑4’s consistency as possible without fine-tuning or additional training (https://runwayml.com/research/introducing-runway-gen-4). The Cast Sheet is a practical way to operationalize that idea in your own process.

Should my Cast Sheet be super detailed?

Not at first. Start with the minimum needed to lock identity and scene. Over-describing can introduce conflicts; stabilize with fewer variables, then add detail only where drift occurs.

What’s the single most important field?

The Prompt ‘anchor’ line, because it’s the reusable constant you paste into every clip.

Can I use images as references?

Many tools support reference-based workflows in different ways. Runway describes combining visual references with instructions for consistent styles/subjects/locations (https://runwayml.com/research/introducing-runway-gen-4). If Veo3Gen supports references in your setup, the same cast sheet still helps you keep instructions consistent.

Related reading

• What is the Veo 3 API?
• Veo 3 API features guide
• Getting started with the Veo 3 API

CTA: Turn this into a repeatable pipeline

If you’re producing multi-clip campaigns, the Cast Sheet method becomes even more valuable when it’s paired with an automated generation pipeline.

• Explore what’s possible with the Veo3Gen API: /api
• See plans and usage options: /pricing

Build one Cast Sheet per “world” (character + location + product), then generate variations by swapping only the clip instruction. That’s how you get continuity without turning every prompt into a novel.

Try Veo3Gen (Affordable Veo 3.1 Access)

If you want to turn these tips into real clips today, try Veo3Gen:

• Start generating via the API: /api
• See plans and pricing: /pricing

Sources

• https://runwayml.com/research/introducing-runway-gen-4
• https://runwayml.com/gen-4-bts
• https://runwayml.com/research/introducing-runway-gen-4.5
• https://runwayml.com/changelog