Shot Design & Visual Consistency

Fabric uses a cinematography vocabulary inspired by Seedance 2.0 Shot Design to produce cinema-grade video from AI models. Instead of vague adjectives like “cinematic” or “high quality”, prompts use specific physical parameters — focal length in millimeters, 3-layer lighting descriptions, and named film stocks — that video models can execute precisely.

This system lives in workflows/video/_shot_design.py and is reusable by any workflow that generates video prompts.

The Problem with Generic Prompts

Most AI video prompts look like this:

A person walking through a city, cinematic, high quality, 4K, masterpiece

This produces generic, “AI-looking” video. The model has no physical parameters to work with — “cinematic” means nothing specific.

The Solution: Physical Parameters

Fabric enriches every b-roll prompt with five layers of physical description:

Close-up of hands typing on a mechanical keyboard.
85mm portrait lens, slow deliberate push-in.
Soft diffused key light from window-right, gentle wrap-around fill,
warm rim separation on edges, golden-hour warmth with soft shadow falloff.
Shot on Kodak Portra 400, fine organic film grain,
individual hair strands catching backlight.
9:16 vertical framing.

The difference in output quality is dramatic. Physical parameters give the model concrete visual targets rather than abstract aesthetic goals.

Segment Shot Library

Every b-roll segment has a narrative type that maps to a default cinematography preset:

Type	Focal Length	Camera Movement	Lighting	Film Stock
hook	24mm wide	dolly push-in	dramatic sidelight, volumetric shafts, teal/amber	Kodak Vision3 500T
problem	35mm standard	handheld drift, micro-shake	harsh overhead, deep shadows, cool blue-grey	ARRI ALEXA Mini LF
insight	85mm portrait	slow push-in	soft window light, warm rim separation, golden-hour	Kodak Portra 400
solution	50mm standard	slow orbital (45 arc)	balanced 3-point, god rays, warm amber	35mm film grain
demo	35mm standard	smooth tracking	clean softbox, rim light, neutral tone	Octane rendering
proof	85mm portrait	static + rack focus	natural window light, atmospheric haze, golden	Fuji Pro 400H
cta	24mm wide	slow crane up	dramatic backlight, lens flare, high-contrast warm	Cinestill 800T

3-Layer Lighting Model

Each preset defines lighting as three components:

1. Source — where the light comes from (e.g., “dramatic sidelight from screen-left”)
2. Behavior — how the light interacts with the scene (e.g., “volumetric light shafts cutting through atmospheric haze”)
3. Color Tone — the palette it creates (e.g., “high-contrast teal shadows with warm amber highlights”)

This maps directly to how cinematographers describe their lighting setups.

Organic Imperfections

Every preset includes intentional imperfections that prevent the “too-clean AI look”:

• Film grain (fine, subtle, or heavy depending on stock)
• Dust motes drifting through light shafts
• Lens flare on highlights
• Bokeh circles in out-of-focus areas
• Halation on bright edges (especially Cinestill 800T)
• Natural optical vignetting

Prompt Assembly Pipeline

The assemble_cinematic_prompt() function enriches a raw b-roll description in 5 steps:

Raw input:  "Person looking stressed at their desk"

1. Strip banned filler words (masterpiece, 4K, 8K, ultra HD, etc.)
2. Determine segment type (hook/problem/insight/solution/demo/proof/cta)
3. Check if LLM already included camera/lighting/material terms
4. If generic → layer in shot preset (focal length + camera + lighting + film stock)
5. Prepend continuity brief

Banned Filler Words

These words actively degrade AI video quality and are automatically stripped:

masterpiece, 4K, 8K, ultra HD, best quality, highly detailed, photorealistic, ultra clear, ultra realistic, hyper realistic, super detailed

Prompt Validation

validate_broll_prompt() checks that a prompt contains all three categories:

• Camera direction — focal length or camera movement term
• Lighting — light source, behavior, or color tone term
• Texture/material — film stock, bokeh, or organic imperfection term

If any category is missing, the assembler fills it in from the shot preset.

Visual Continuity Brief

The continuity brief is a 1-2 sentence prefix prepended to every visual prompt in a video to maintain consistent aesthetics across all segments.

How It Works

1. Mood mapping — The video’s mood keyword (e.g., “high-energy”, “moody”, “documentary”) maps to a film stock and base palette:

Mood	Film Stock	Base Palette
high-energy, energetic	Kodak Vision3 500T	warm amber + teal shadow accents
conversational, casual	Kodak Portra 400	warm neutral + soft golden highlights
serious, dark	ARRI ALEXA Mini LF	desaturated cool + neutral midtones
moody, night	Cinestill 800T	cool blue-green + neon-warm highlights
cinematic, dramatic	Kodak Vision3 500T	rich contrast + warm highlights + cool shadows
inspirational	Kodak Portra 400	golden warmth + soft diffused highlights
educational, documentary	ARRI ALEXA Mini LF	naturalistic palette + muted tones

2. Dominant segment type — The most frequent b-roll segment type determines the color tone from its shot preset.

3. Output — A string like:

Unified palette: warm amber base with teal shadow accents.
Consistent Kodak Vision3 500T grain across all shots.
Atmospheric haze present in every frame.

This brief is stored as script["_continuity_brief"] and prepended to:

• Every b-roll generation prompt
• Every talking-head generation prompt

Relationship to Keyframe Grid

The continuity brief provides textual consistency (color grading, grain, atmosphere). The keyframe grid adds visual consistency (pixel-level lighting geometry, character details). Both systems work together — the grid prompt itself includes the continuity brief.

Using Shot Design in Custom Workflows

The module is importable from any workflow:

from workflows.video._shot_design import (
    assemble_cinematic_prompt,
    validate_broll_prompt,
    strip_filler,
    get_shot_preset,
    generate_continuity_brief,
    SEGMENT_SHOT_LIBRARY,
)

# Enrich a plain description
prompt = assemble_cinematic_prompt(
    narration="The future of renewable energy",
    broll_desc="Solar panels stretching across a desert landscape",
    segment_type="solution",
    segment_index=2,
    total_segments=5,
    continuity_brief="Unified palette: golden warmth...",
)

# Check prompt quality
passed, missing = validate_broll_prompt(prompt)
if not passed:
    print(f"Missing: {missing}")

# Get raw presets
preset = get_shot_preset("hook")
print(preset["focal_length"])  # "24mm wide-angle lens"