Chapter 2: Interaction Prompts & Diegetic UI

Created by Sarah Choi (prompt writer using ChatGPT)

Interaction Prompts & Diegetic UI for Prop Concept Artists: On/Off, Open/Closed, Damaged, and Crafted States

Interaction prompts are the handshakes between player and prop. Diegetic UI is the version of that handshake which lives entirely inside the world: labels, lights, meters, chimes, haptics, and mechanical tells that guide behavior without a floating button. When these systems are designed as part of the prop’s identity—and not pasted on at the end—they shape clarity, pacing, and immersion. This article offers a principle‑driven approach to designing prompts and diegetic UI for the core state families—on/off, open/closed, damaged, and crafted—so that both concept and production artists can ship readable, performant, and tasteful assets.

Start with a single sentence of intent for each interaction: what the user should do and why now. Do not design icons or lights before you know the verb. “Press to arm plasma welder” leads to a very different prompt system than “Hold to purge coolant” or “Align to dock battery.” Once the verb is clear, write a minimal cue bundle: one global signal for spotting at distance, one local signal at the affordance, and one confirm signal after the action. If the interaction is reversible, include a state‑change signal that lingers (e.g., a latched position, a persistent color shift, a new hum).

On/off prompts should be more than a lonely LED. A good power cue is layered: the shell changes value from matte to semi‑gloss near heat sinks, a ring light breathes slow when idle and locks solid when armed, a tiny e‑ink tag flips from “OFFLINE” to “READY,” and the switch itself has an obvious high/low geometry. Keep power prompts consistent across a family, so readiness reads in silhouette and value even before lights. Avoid relying solely on hue; pair color with shape, rhythm, and roughness change so the prop reads in grayscale, dust, or glare.

Open/closed prompts live at seams and latches. Design arrow choreography and number logic that teaches the motion: align, press, rotate, pull. Use keyed geometry—D‑shaped bosses, asymmetric tabs, captive fasteners—to narrate correct orientation. Inside, let a brighter service palette and low‑level work lights announce “open” without UI popups. If safety matters, include a mechanical interlock that visibly disengages only when power is isolated. The best open/close prompts acknowledge ergonomics: finger reliefs, knurling where grip is needed, and short labels that front‑load verbs (“PRESS TO RELEASE”).

Damage prompts must balance spectacle with clarity. Failure should tell the user what not to do, what risk exists, and where a fix might start. Use status clusters that degrade asymmetrically: two bars dead, one flickering, one solid. Let mechanical drift reveal misalignment: a latch no longer seats flush, a fan wobbles, a gasket extrudes. Pair with diegetic overlays like inspection tags, out‑of‑service bands, or lockout hasps to prevent interaction. If repair is an option, design prompt‑like hints inside: diagnostic lights near test ports, braid color coding on swappable harnesses, or QR‑like glyphs that imply a service manual exists in‑world.

Crafted prompts should feel learned, not corporate. Field‑made upgrades speak through mismatched parts and improvised cues: hand‑scrawled arrows in paint pen, heat‑shrink labels on new cables, a repurposed e‑ink label powered by a piggyback board. Keep the interaction verbs the same as stock where possible, but let cadence change—a toggle becomes a detented rotary, a single press becomes “press and hold.” Diegetic UI on crafted props should inherit the base brand’s geometry so it remains believable; a beautifully milled aftermarket plate tells the story of a skilled maker while preserving the layout logic.

Readable prompting depends on hierarchy and proximity. Global prompts are for discovery: a slow breathing edge, a bright handle, a band of color that cues “this is the side you interact with.” Local prompts are for execution: a crisp arrow next to the latch, a numbered torque pattern around a cap, a ring light that fills as pressure equalizes. Confirmation prompts are for confidence: a mechanical thunk, a latch that sits flush, an indicator that moves from amber to solid blue. When possible, let the geometry perform the confirmation so the signal survives without power or audio.

Typography and iconography are the backbone of diegetic UI. Use a technical sans with strong distinction between ambiguous glyphs, tabular figures for numbers, and a slashed zero. Keep icon families on a shared grid, with strokes that match the text’s optical weight at the smallest intended size. Favor literal verbs: arrows that arc along the exact hinge path, rotation icons that match detent count, and simple metaphors for energy, heat, and pressure. Pair with two‑letter codes to reinforce (“HV,” “VAC,” “SVC”). For multi‑language worlds, stack two short lines rather than one long string, and leave room for expansion.

Light is your most flexible prompt channel, but it must be disciplined. Use shape‑based emissives—rings, bars, chevrons—over dots. Design time signatures that align with human perception: readiness breathes slowly, progress sweeps linearly, errors pulse sharp and then settle. Modulate roughness and normal around light pipes so edges catch a soft bloom. In noisy scenes, reduce saturation and let luminance do the work; bright white bars are often more readable than deeply colored LEDs. Reserve intense color shifts for state transitions and lock them to mechanical events so they feel causal rather than ornamental.

Sound and haptics can be implied even when muted. A soft relay click, fan ramp, or valve hiss is familiar; if your context disallows audio, let small motion cues stand in. Micro‑vibrations, bouncing needle gauges, or sympathetic cable sway can sell engagement. For haptics in controller contexts, let pulse patterns mirror emissive rhythms so prompts remain consistent across senses.

Material and process choices determine whether prompts survive production. E‑ink labels are excellent diegetic UI for low‑power, late‑binding states; they also read in bright light and at odd angles. Laser‑etched icons carry through wear and oil; pad‑printed legends are crisp but will scuff on high‑touch surfaces. Light pipes diffuse better through frosted polycarbonate; opaque housings benefit from thin reveal gaps rather than holes. Call out process in concept so production maps prompts to basecolor, roughness, normal, emissive, and mask channels correctly.

Diegetic UI must be accessible and robust. Never encode meaning in color alone; pair hue with shape, position, and text. Increase contrast and stroke at the smallest sizes, and wrap light shapes with subtle keylines to hold edges against glare. For right‑to‑left locales, do not mirror mechanical arrows that indicate physical direction, but do mirror layout flow where it relates to order of operations. Where numerals are critical, prefer tabular figures and avoid ambiguous characters. Consider colorblind palettes when assigning state hues; blue vs. amber is more reliable than green vs. red.

Pipeline hygiene turns design into repeatable results. In concept, deliver an interaction sheet: the verb, the global/local/confirm cues, and the timing plan. Include icon vectors, typographic styles, emissive masks, and geometry callouts with pivot and clearance notes. In production, separate icon atlases from localized strings; keep emissive masks in their own texture so intensity can be tuned per prop. Use mesh decals for late‑binding prompts like “LOCKOUT” or “SERVICE”—they should be swappable without touching UVs. Drive state changes with material parameters where possible rather than unique textures.

Testing prompts is a simulated encounter, not a static inspection. Walk the camera toward the prop from typical approach angles and under varied lighting; if the global cue does not attract notice at the right distance, adjust value or silhouette. Execute the interaction and watch for causal timing: do lights and sounds lead or lag the mechanism? Check temporal stability under TAA and motion blur; if a small LED shimmers, convert it to a ring or bar. Print at 1:1 for practical builds and verify finger clearances, reading angles, and latch forces.

Ethics and narrative discipline matter. Interaction prompts should not trick the user with hostile patterns unless the story demands it; if deception is a theme, embed tells so the audience can learn the con. Avoid real‑world restricted marks that imply certification. Respect cultural meanings in icons and numbers. If a villain faction borrows an industrial safety pattern, alter geometry and cadence so it reads as appropriation, not plagiarism.

Deliverables that downstream teams love include a compact “interaction bible” per prop: a one‑page state chart, a vector prompt kit with icons and labels, emissive mask and timing guides, annotated orthos for placement and pivots, and a wear plan that shows how prompts age without losing meaning. When prompts and diegetic UI are authored with this rigor, players feel smart, shots cut cleaner, and your props graduate from decorated models to readable machines in a living world.