SL-82 / World Effects

Reactive Fog

The person edits the effect: fog parts at the shins and settles after.

The brief

Low fog that opens in a wake as a body moves through it, curls into vortices off the trailing leg, and takes seconds to slump back level.

Why it's hard

Generated fog is a uniform layer sliding across the frame, completely untouched by the person supposedly walking through it.

The craft key

The effect must be downstream of the body. Specify the wake, the vortices and the settling time.

Skill Tests

03 / 28
Animal anatomy Human anatomy Biomechanics Physics & mass Water simulation Crowd dynamics Multi-shot continuity Face consistency Camera movement Unbroken take Motivated lighting Cutting rhythm Hands & fingers Hair & fabric Reflection & refraction Scale & depth Impossible geometry Period accuracy Music sync Aging & time Natural asynchrony Eye-lines & gaze Particle behaviour Motivated light source Consequence & persistence Time manipulation Graphic-layer discipline Colour as storytelling

Every challenge is scored against the same vocabulary, so you can compare them. Lit cells are what this one tests.

Starter prompt

Built with the CEMI MediaMax system for Google Veo 3.1. Prompts stay in English — that is the language these models take instructions in. Treat it as a starting point and start varying it.

reactive-fog
Slow lateral tracking shot on a shoulder rig, 35mm anamorphic at f/2.8, a river meadow before sunrise with ground fog lying knee-deep and level as milk. Wet reed heads sweep through the extreme foreground, streaking the frame. A figure in oilskin and rubber boots walks left to right through the fog bank: the fog parts in a clean wake at their shins, curls into twin vortices spinning off the trailing leg, and takes three or four seconds to slump back to a level surface — the body edits the effect, and the meadow briefly remembers where they walked. The fog stays below the waist; the air above stays clear. Christopher Doyle's saturated pre-dawn blues and hand-carried instability. The operator's footfalls read as vertical bounce. Oval bokeh, barrel distortion at the edges, focus breathing as the figure passes.

Derived from the CEMI MediaMax production canon — cemi.media

Style reference: Christopher Doyle

Why it's built this way

Reactive fog is the clearest test of diegetic discipline: the effect must be downstream of the body, not layered over it. Specifying the wake, the counter-rotating vortices off the trailing leg, and a settling time gives the model a causal chain instead of a texture. Holding the fog below the waist keeps a hard physical ceiling that proves it is a fluid sitting in cold air, not an overlay.

Watch for

A uniform fog layer that slides across the whole frame untouched by the walker — no wake, no vortices, and no settle after they pass.

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