Chapter 2: Oceans: Waves, Foam, Translucency, Tide Zones

Created by Sarah Choi (prompt writer using ChatGPT)

Oceans — Waves, Foam, Translucency, Tide Zones (Hydrology for Environment Concept Artists)

Why ocean logic matters

The sea is a moving light source, a sculptor of coasts, and a metronome for time. When waves, foam, color, and tides obey physics, players stop noticing the simulation and simply feel “near the ocean.” This article distills oceanography into visual logic and production‑ready cues for both concepting and build.

Wave basics you can sketch from memory

Waves are energy traveling through water, not water traveling long distances. A single patch of water mostly moves in orbits.

  • Deep‑water waves: Orbits are circular and diminish with depth; seabed is not felt. Period (T) and wavelength (L) relate: faster, longer‑period swells outrun shorter chop and arrive first after storms.
  • Shoaling: As depth decreases to ~½ L, waves “feel bottom,” slow down, shorten, and grow taller. Orbital paths squash into ellipses; forward velocity concentrates at the crest.
  • Breaking types (set the mood):
    • Spilling breakers: Gentle beach slopes; whitewater spills down the face for long distances—soft, friendly surf.
    • Plunging breakers: Intermediate slopes; a curling lip pitches forward—dramatic tubes and loud thunder.
    • Surging/collapsing: Steep or reflective shores; wave doesn’t fully break, runs up as a surge and slaps back—booming cliff lines.
  • Sets: Swell arrives in packets (group velocity). Use lulls and sets to rhythm level pacing at shorelines.

Concept cues: Longer‑period swells = smooth, widely spaced lines with strong refraction around points; short wind‑chop = tight, chaotic texture that damps quickly in bays.

Wave direction, refraction, and longshore drift

Wave crests bend (refract) to align with depth contours. Energy focuses on headlands and diffuses in bays, driving coasts toward pocket‑bay spirals. Oblique incidence drives longshore currents, moving sand down‑coast and shaping spits and tombolos. Rip currents form where water returning from the swash converges into narrow outbound jets—look for darker, choppier lanes cutting across breakers.

Production: Use a depth‑derived normal/wave steering map to rotate normal textures toward shore normal near the break zone and bend around headlands. Spawn foam streaks that slide along longshore vectors; leave darker rips with less foam and more specular.

Foam: the ocean’s calligraphy

Foam reveals turbulence. It forms when bubbles from breaking waves and turbulent bores reach the surface and cluster.

  • Where it lives: On breaker crests at impact, in the collapsing face, as a bore in the swash zone, in foam lines along shear zones/eddies, and as spume blown off crests in gales.
  • Lifecycle: Bright and fine‑bubbled at birth, coalescing into larger flakes, decaying into rafts and strings, then vanishing.
  • Patterns to stage: Crescent “cat’s paw” patches in wind gusts; lacework along rip boundaries; curved tongues wrapping around shoals; long foam streets aligned with wind.

Production:

  • Multi‑stage foam masks: (1) impact/crest, (2) advected sheet, (3) decay/patches. Fade by age.
  • Sample slope and curvature to trigger birth; advect by surface flow field; clamp in the swash zone by run‑up height with hysteresis so it lingers as sheets.
  • Tie foam brightness to view angle and shadowing; under overcast, raise diffuse, lower spec.

Ocean color and translucency: painting with absorption and scatter

Seawater selectively absorbs red and lets blue‑green penetrate; suspended matter adds scatter.

  • Clear open ocean: Deep blues/cyans; strong Fresnel reflection at glancing angles, transmission green‑blue at normal angles. Caustics visible in shallow sand patches.
  • Coastal green: Phytoplankton and suspended silt shift color toward green or jade; surf becomes milky when laden with microbubbles and sediment.
  • Tropical lagoons: Bright turquoise over pale sand; rapid transition to deep indigo at reef drop‑offs (the “blue edge”).
  • Tannin/brownwater plumes: Tea‑colored outflows at river mouths; sharp color fronts at estuarine mixing zones.

Production:

  • Use depth‑based color attenuation (exponential) with separate coefficients for R, G, B; drive turbidity by proximity to rivers/shore and by storm state.
  • Implement screen‑space or vector caustics in <5–8 m depths; modulate scale by depth. Avoid caustics in rough water or deep shade.
  • Fresnel term: low roughness in calm leeward coves, higher roughness and microfoam sparkle on windward fetches.

Transparency, subsurface, and the shoreline band

  • Backlit shallows: Expect bright subsurface glow as light transmits through the thin crest; strongest in clean swell and sandy bottoms.
  • Swash zone: Thin water sheets oscillate up and down the slope; you see specular streaks, foam lace, and moving wet‑sand darkening.
  • Wet sand memory: Berm edges retain dark dampness after waves recede; footprints persist only in cohesive damp sand.

Production: Create three bands: offshore (no bottom read), nearshore (partial bottom contribution + caustics), swash (wet sand/foam sheets). Blend with a beach profile mask driven by tide level and wave height.

Tide systems: clocking vertical motion

  • Types: Semi‑diurnal (two highs/lows daily), diurnal (one), mixed (unequal). Spring tides (higher range) occur when Sun and Moon align; neaps (lower range) at right angles.
  • Range: Microtidal (<2 m) favors stable beaches and narrow intertidals; macrotidal (>4 m) exposes vast flats, strong tidal currents, and dramatic bore waves in constrictions.
  • Tidal currents: Inlets and headlands funnel fast flows that create eddies, whirlpools, and slick lanes; sediment stripes align with flow.

Concept cues: Include an intertidal bio‑band ladder: dark algal film at low intertidal, barnacle/limpet texture above, pale lichen/salt spray zone higher. On macrotidal coasts, stage scenes on exposed flats with megaripples, worm casts, and tidal channels at low tide, then flood the arena at high tide.

Production: Drive global tide height as a parameter that shifts shoreline blends and exposes intertidal decals. Animate tidal creeks filling/draining; reverse flow arrows in inlets between flood and ebb.

Rocky shores, reefs, and kelp lines

  • Wave‑cut platforms: Gently seaward‑sloping benches with tide pools; slick algae bands near low tide; hematite/iron staining beneath seeps.
  • Boulder beaches: Rounded blocks organized by size with largest at storm limit; booming surf and quick backwash.
  • Fringing & barrier reefs: Surf line breaks on reef crest; calm lagoon inside with patch reefs and sand channels (spur‑and‑groove). Coral rubble ramps on the fore‑reef.
  • Kelp forests: Sit in cold, nutrient‑rich upwelling zones; fronds mark current direction; rafts collect windward of headlands.

Production: Place tide‑pool biota and reflective films in protected platform pockets; spawn barnacles/limpets up to a consistent elevation; align reef “spurs” perpendicular to wave approach; sway kelp with a low‑frequency current vector plus high‑frequency wave surge.

Storm states and seasonal switching

  • Calm: Long glassy lines, little foam, strong reflections. Beaches accrete with steep berms.
  • Windy: Short chop over swell (“cross‑sea” patterns), whitecap percentage rises with wind speed; foam streets align with wind.
  • Storm: Brown/gray water, suspended sediment, high run‑up, beach scarping, dune overwash, blown spume.
  • Seasonality: Winter storms strip sand to offshore bars; summer calms rebuild beaches.

Production: Bundle multiple ocean “presets” (calm, breezy, storm, post‑storm) that swap foam thresholds, turbidity, and beach profiles. Leave physical traces—storm wrack lines, scarped berms.

Sound, camera, and timing as ocean design tools

  • Cadence: Use wave sets to time reveals and traversal windows across tidal platforms. Calm lulls for dialogue; crash peaks for tension.
  • Camera: Low angles near the swash exaggerate scale; high over headlands shows refraction and longshore drift.
  • Audio: High‑frequency hiss for spilling surf; deep thump for plungers; clatter of cobbles on reflective beaches; wind howl during spume events.

Implementation crib sheet (tech + art)

  • Surface: Combine large‑scale Gerstner/FFT for swell with tileable normal packs for chop; steer normals by depth‑derived direction field.
  • Foam: Curvature + velocity thresholds for birth; age/advect; distinct masks for crest, sheet, residue.
  • Color: Depth/turbidity‑based attenuation; Fresnel reflection; volumetric absorption under crest; optional god‑rays in clear, shallow water.
  • Shoreline: Run‑up solver or proxy sinusoid to move swash; wet‑sand darkening with time constant; footprints only in damp band.
  • Tide: Global parameter offsets shoreline masks; animate intertidal population exposure; reverse inlet flows.
  • Performance: Bake distant ocean to scrolling normal/spec cards; LOD foam particles; cap reflection ray depth; avoid aliasing with temporal smoothing of foam masks.

Common pitfalls and quick fixes

  • Uniform foam carpet: Spawn only where breakers occur; decay with age; remove from lee coves on calm days.
  • Blue everywhere: Add turbidity near rivers/coasts; introduce color fronts and sediment plumes after storms.
  • Waves ignoring headlands: Add refraction steering and energy damping in bays; bend foam lines around points.
  • Static shoreline: Animate run‑up, leave dampness memory, move wrack line after storms.
  • Tide‑agnostic intertidal: Place bio‑bands at consistent elevations; expose tide pools at low tide only.

Field studies for concept practice

  • Paint a pocket bay showing refracted swell, longshore drift forming a tombolo, and a rip carving a dark lane through the break.
  • Design a macrotidal platform scene at low tide with tide pools, megaripples, and creek channels; re‑light the same shot at high tide with surging bores and kelp streaming.
  • Block a reef‑lined tropical coast: surf detonates on the crest, calm lagoon inside with sand tongues and patch reefs, then a blue drop‑off.

Final checklist

  • Do wave period, height, and breaker type match the shoreline slope and wind state?
  • Are foam, color, and translucency changing with energy and water depth?
  • Do refraction and longshore drift organize beach shape and sediment cues?
  • Do tide zones and bio‑bands sit at consistent elevations with believable exposure times?
  • Are shoreline interactions (swash, wet sand, wrack) animated and leaving memory in the scene?

Let waves write the rhythm, foam trace the impact, color reveal the depth, and tides turn the pages. When each of these systems talks to the others, your ocean scenes will feel unforced, legible, and alive.