Prompt Expander

Prompt expander

Turn a rough idea into a complete, generation-ready cinematic prompt — by deliberately deciding every dimension a clip can express, then writing only the relevant choices as natural prose.

Written against Gemini Omni Flash in Google Flow (~10s clips with synced audio; accepts text + reference image/audio/video; supports multi-turn conversational editing). The dimension model transfers to any video generator; the mechanics in §B of the audio reference are Omni-specific.

When to use: someone hands you a logline and wants it "expanded" · you are writing or polishing a Flow prompt · you want to edit an existing clip (use the Editing path, not full expansion).

The dimensions — think through ALL of them

For every prompt, consciously decide each axis, then keep only what serves the idea:

Read the reference for any axis you are unsure how to fill. Do not paste the menus into the prompt — choose a few options and write prose.

Workflow

1. Parse the idea: pull out subject, action, setting, and any stated mood, genre or audio.
2. Classify: a fresh generation, or an edit of an existing clip? An edit goes to the Editing path below.
3. Fill the gaps: for each of the 8 dimensions, choose options that fit the mood. Use the defaults table for anything unspecified.
4. Respect the constraints (audio reference §B5): one beat per ~10s · always specify audio · phrase exclusions positively · do not rely on rendered on-screen text · keep references to a few.
5. Write the prompt as flowing prose in this order: camera → subject → action → setting → light/style → audio. Add a timestamp breakdown only if there are genuinely 2–3 beats.
6. Lint the result — veo-prompt-lint — and fix any ERRORs. If that is unavailable, self-check against the Common mistakes list below.
7. Present three things: the prompt block, a short Levers list of the assumptions you made so they can be tweaked, and 1–2 suggested conversational edits for iterating.

Sensible defaults (when the user is silent)

State the defaults you used in the Levers list. Never silently bury a consequential choice.

Ask vs. assume

Default to assuming and proceeding, noting it in Levers. Ask only when a choice is both consequential and genuinely ambiguous — almost always one of: realistic vs. animated/stylised, dialogue vs. silent, vertical vs. widescreen. Bundle those questions; do not drip them one at a time.

Editing path (an existing clip)

Use the surgical rule from the audio reference §B1:

• One change per turn. Isolate a single dimension; verify before the next edit.
• Freeze-list: name explicitly what stays. Change <X>. Keep the camera, subject, location, timing, and audio identical.
• Batch changes as a numbered list, ending with the same freeze line.
• Remember: editing the spoken audio of a clip is currently restricted.

Worked example

Idea: "a lonely astronaut finds a flower on a dead planet"

Expanded prompt:

Slow push-in, low-angle medium shot on a weathered astronaut in a scuffed white EVA suit, cracked gold visor reflecting a dim red sun, kneeling on cracked ochre desert rock. He slowly reaches a trembling gloved hand toward a single impossible blue flower pushing up through the dust; grit drifts in the low gravity. Vast empty rust-coloured plain stretches to a hazy horizon behind him, distant dust devils. Bleak desaturated palette with one vivid blue accent, harsh low sunlight, 35mm film grain, melancholic and awestruck. Ambient: faint wind and the hiss of suit air. SFX: soft servo whir as his hand moves. No dialogue, no music.

Levers: photorealistic (could go painterly) · 16:9 (could be 9:16) · silent (could add a breath or VO) · single push-in (could add a [00:06-00:10] insert close-up on the flower).

Suggested edit: Change the flower from blue to glowing bioluminescent teal. Keep the camera, subject, location, timing, and audio identical.

Common mistakes

• Pasting whole menu tables into the prompt — pick a few options, write prose.
• Forgetting audio → the model invents unwanted speech.
• Cramming a multi-scene story into 10 seconds — one beat.
• "no people / no text" phrasing → flip it positive ("a deserted street", "a clear sky").
• "locked tripod" → use "static shot".

The reference menus