Chapter 3: Energy Reservoirs & Cooldown Logic

Created by Sarah Choi (prompt writer using ChatGPT)

Energy reservoirs & cooldown logic (for prop concept artists)

This article gives concept and production artists a shared, buildable grammar for “how power is stored and rests” in magical or techno‑mystic artifacts—wands, foci, catalysts, reliquaries and setpiece machines. It translates gamey ideas (mana bars, ult meters, cooldowns) into physical design: reservoirs with believable capacity, conduits with bottlenecks, and recovery states that read clearly on camera without relying entirely on VFX. Use it to design hero props, inventory icons, and diegetic UI that survive the handoff to modeling, rigging and lighting.

Reservoirs, conduits and sinks: the core triad

Every energy system needs (1) a reservoir that holds charge, (2) conduits that move it, and (3) a sink that dissipates waste (heat, ash, echo). Give each role a material and geometry:

  • Reservoirs favor volume and containment: glass bulbs, crystal cores, coiled metal springs, wound cords, bone cavities, pressurized phials.
  • Conduits favor path and direction: engraved channels, braided wire, capillary tubes, dovetailed inlays, threaded rods.
  • Sinks favor surface area: fins, perforations, vents, sand beds, salt plates, heat‑band wraps, iron rings to ground. Design reads improve when these three are visible and distinct—audiences intuit how power leaves storage, passes through a control aperture, and sheds cost into the world.

Capacity by silhouette: how full looks

Make capacity legible without numbers.

  • Glass/liquid reservoirs: show a meniscus and a headspace; fullness is a clear height. Gas bubbles track agitation. Suspended sediments gather at the bottom as “spent.”
  • Crystal reservoirs: glow occupies internal veils; higher charge lights deeper planes first, then creeps to outer facets. Micro‑sparks pin at inclusion points.
  • Coil/spring reservoirs: mechanical energy language—tight wind = charged, slack wind = spent. Index marks and pawls give readable states.
  • Bone/organic reservoirs: inks or resins stain pores; saturation darkens cortical shell and wicks into carved canals.
  • Metal capacitors: charge shows as corona along knurled edges, faint St. Elmo’s at tips, or magnetized grit aligning near poles. Anchor each with a physical index: alignment notches, tally beads on a cord, a rotating scale ring, or a windowed slot with a moving indicator pellet.

Cooldown as physiology

Treat cooldown like breath and pulse. After discharge, the artifact “pants”: vents warm, glass fogs then clears, crystals ring down with damped shimmer. Visualize three decay constants—fast (flash dies in conduits), medium (reservoir dims), slow (sink bleeds heat). Stage each with different materials so decay reads in layers: the channel goes dark first, then the core, while the fins remain hot and shimmering. If sound is present, sync to a falling pitch and wider intervals.

Bottlenecks and gates: where control lives

Place a constriction between reservoir and output to explain rate‑limit and cooldown. Gates can be:

  • Mechanical: iris diaphragm, screw stop, ratcheted collar, escapement wheel that clicks as energy increments pass.
  • Material: choke stones (porous crystal wafers), saturable metal rings, wax fuses that melt open and later re‑set.
  • Geometric: narrow necks in glass, thin sigil bridges, long capillaries that enforce delay. Cooldown begins at the gate: it must reset, clear heat, or re‑align. Give it a return‑to‑zero gesture—an iris closing, a detent snap, a bead sliding home.

Overcharge, venting and fail‑gracefully cues

Audiences love edges. Define what “too much” looks like before it breaks.

  • Glass: rainbow stress fringes at mounts, micro‑cracks radiating from screws, frost bloom near collars, corks weeping.
  • Crystal: wandering interference bands, facet “ghosts” doubling, tiny lightning that refuses the intended channel.
  • Metal: straw‑to‑blue heat tints, solder weeps, rivet halos.
  • Bone: resin sweating from pores, hairline craze along carved tracks. Give a sacrificial path: burst disk, frangible bead, fusible link, salt plug that spits and crumbles. Paint a thin soot kiss trailing from the relief port so the camera already knows where failure will narratively go.

Cooldown UX: readable states without UI

Build a five‑state diegetic system that works even in stills:

  1. Idle — silent, cool; reservoirs show faint depth, conduits dark, sink matte.
  2. Primed — subtle pre‑glow at the gate; valves center; index beads tremble; faint breath from vents.
  3. Active — conduits emit, reservoir brightens, sink heats (shimmer/rivulets).
  4. Saturating — emission spills beyond intended paths; warning LEDs, talismans or chimes tick faster; overcharge cues appear.
  5. Cooldown — conduits dark first, reservoir coasts down, sink radiates last; droplets/condensation form and vanish; audible tick‑tick of contracting metal. Establish this cadence across your artifact family so players learn it once.

Recharge models: time, fuel, trade

Decide how power returns:

  • Time‑based (natural recharge): ambient light filling a photonic vial, dew condensing in a salt cell, a crystal re‑phasing to the world field. Show passive cues like sun‑grazed caustics inching across a scale.
  • Fuel‑based: poured reagents, swappable cells, bone beads sacrificed from a rosary. Depict funnels, bayonet sockets, knurled caps, drip stains below fill ports.
  • Trade‑based: the wielder’s stamina, heat from a forge, sound from a chant. Offer interfaces—grip plates that warm, tuning forks that must be struck—so recharge is participatory. Each model suggests different cooldown chores: wiping frost, reseating seals, re‑winding springs, or burying the tool in salt to pull heat.

Thermal language: making “hot” read

Heat is the most universal sink. Use:

  • Fins and lattices sized to surface area; orient them vertically so convection feels right.
  • Color tints on metals (straw, brown, purple, blue).
  • Heat bands—fabric wraps with small thermostats and cloth ties—for safe handling.
  • Mirage shimmer near vents; tiny lifting smoke in high stakes.
  • Handling logic: leather grips away from hot zones, insulating washers at fasteners, fold‑out stands to keep hot parts off surfaces.

Temporal locks and interlocks

Cooldown can also be permission. Add interlocks that refuse operation until cooled: a bimetal strip that straightens only when cold, a wax seal that rehardens around a pin, an hourglass that must drain, frost that must thaw to free a latch. These props create diegetic gating for puzzles and give actors business between uses.

Stacking and combo logic

If your world supports combos, make stacks visible. Beads along a haft slide forward per cast; three filled sockets around a crystal unlock a higher‑order path; a rotor advances one tooth per discharge until it hits a glyph. After a finisher, forced cooldown blows through all sinks—vents yawn, seals sigh, beads spring back—so the prop reads “empty and locked,” not merely dim.

Materials that pace cooldown

Pick materials that metabolize energy at different speeds so cross‑fades feel natural:

  • Glass cools slowly, shows fogging/clearing.
  • Crystal discharges quickly but rings with after‑images.
  • Bone soaks heat into mass and dries slowly, leaving salt bloom.
  • Metal conducts to fins; thick sections stay warm; thin ones ping as they relax. Arrange them from fast to slow along the flow to create a literal cooling gradient you can light and animate.

Wear, repair and maintenance rituals

Cooldown breeds maintenance. Include wipe marks on glass near vents, resin drips under fill ports, heat‑scorched leather wraps, and discolored washers. Add repair affordances: spare burst beads tied on with twine, a tiny torque‑seal swipe across a set screw, a chalk tally of discharges on a bone panel. Maintenance rituals (sprinkling salt, oiling a hinge, humming a note to re‑phase a crystal) are cinematic and anchor worldbuilding.

Composing reservoirs with sockets and stands

Give reservoirs safe rest states. Cradles with soft mouths accept hot glass; forked bone stands keep crystal tips off tables; grounded plates with braided straps discharge static. Sockets should have keys and witness marks so reassembly is idiot‑proof. Caps and sheaths should occlude emitters and expose only cooled grips.

Diegetic read next to PPE

When artifacts mix with hazardous industry, echo lab logic. Put a small thermometer or strip indicator on a heat sink, a manometer bulb that rebounds as pressure falls, or a color‑change spot on a shield. Pair with PPE: face shield hanging by the workstation, heat mitts near the stand, an eyewash bottle adjacent to overpressure vents. This quietly legitimizes your cooldown choreography.

Lighting & VFX hooks

Model emissive from within geometry—trenches, lenses, flag‑flip magnetic indicators—so the prop reads even if VFX is off. Provide two or three glow masks: conduits, reservoir core, sink edge. Expose a “heat only” pass: non‑emissive, just refractive shimmer and tint. Give VFX a simple state table (idle/primed/active/saturating/cooldown) with timings and triggers (gate angle, bead position).

Production notes: what concept should call out, what production must preserve

Concept callouts should specify reservoir type and volume cue, conduit pattern and cross‑section, gate mechanism, sink style, interlocks, overcharge relief path, and at least one recharge method. Provide orthos with state overlays and arrows for flow. Production should preserve wall thickness in glass, facet logic in crystals, heat‑tint masks on metals, and pore direction in bone. Rig gates with real arcs and detents; set pivot clearances for moving fins or shutters. Shading should include subtle internal scattering for reservoirs and believable oxide stacks for heat.

Quick checks before handoff

Ask: Does the artifact show where charge lives, how it leaves, and where the cost goes? Can the audience tell at a glance whether it’s idle, ready, or locked out? Is failure prefigured by a sacrificial path? Do materials stage a cooling gradient? If yes, your reservoir and cooldown logic will read without exposition and will scale from thumbnail to hero close‑up.

Depiction‑only note: This guide focuses on visual plausibility for entertainment design. Use fictional brands and symbols; avoid copying real compliance text; let structure, material and controlled light sell the rules of your magic.