Heat Shimmer

Distortion Amount is the “how much” dial, and it decides whether you’re doing photography or graphics. The default Distortion Amount = 10 is visible on a locked-off shot without announcing itself as an effect; Distortion Amount 5–15 covers pavement, exhaust, and candle flames; by Distortion Amount = 20 the bend has stopped reading as air and started reading as a force field. The slider stops at 50 and the hard range runs to 100 — that upper country is for stylized fields, not for plates. Judge it with Render set to Displacement, where nothing else is covering for it.

The heat pass is what separates this from a wobble. Heat Amount sets how much detail the most distorted regions lose: at the default Heat Amount = 50 the hot regions visibly soften while the calm parts of the frame stay sharp, and Heat Amount = 0 turns the stage off entirely. Heat Bias decides how much of the frame the softening covers: lower it and the blur spreads wide, raise it and it retreats to the strongest pockets of the field. Start from the default Heat Bias = 0.5, then move it with Render on Heat and stop where the softening sits on the regions you meant to haze — spread too wide it takes the whole frame with it, pulled too tight it reads as isolated pockets rather than atmosphere. Heat Softness then smooths the handoff between softened and untouched. At Heat Softness = 0 you can see where the blur starts and stops — each hot region gets an edge of its own; the default Heat Softness = 5 hides that on most plates, and Heat Softness 10–20 is the fix when the softened patches still read as shapes instead of as air. Balance the two amounts against each other: heavy Distortion Amount with no heat is a clean glassy warp — right for a shockwave, wrong for hot air — while a light bend with a generous Heat Amount gives the soft breathing patches of very hot, very still air seen from a distance.

Noise Pattern is the first thing to audition and the hardest thing to describe on paper. Switch Render to Field, step through Flame (the default), Smoke, and Ember on your own plate, and keep the one whose structure sits where the heat belongs — busy where the source is, quiet where it isn’t. Noise Scale sets feature size: low values give the tight fizz of air coming off hot metal, the default Noise Scale = 100 suits a mid shot of pavement, and Noise Scale 200–400 gives the fat slow masses that read as a whole atmosphere rather than a single source. Noise Complexity is the octave count — Noise Complexity 1–2 for a smooth field and cheaper renders, the default Noise Complexity = 3 for most plates, Noise Complexity 6–8 when the field should break into filigree.

Four dials shape that field before either stage reads it. Noise Gamma reshapes its distribution — the dial for how much of the frame is doing anything at all. Noise Gamma = 1 is neutral; above it the field thins toward sparse tendrils, below it fattens into a dense full-frame wash — judge the move with Render on Field. Noise Aspect stretches the field along one axis: positive pulls it into the vertical columns of convection, negative lays it into the flat layers of stratified air over a long road — and the positive side pulls harder for the same move. The default Noise Aspect = 0 is neutral, and small moves show — Noise Aspect 0.2–0.4 is already a plain stretch. Noise Offset slides the field without changing the pattern — the way to move structure off a face or onto a hot spot — and it keyframes, so a slow linear offset is an alternative to wind. Noise Seed re-rolls the field for when the structure lands badly and you want a different draw rather than a different look; two instances at different seeds give you two independent fields to stack.

Noise Speed is evolution in place: features form and dissolve without going anywhere, which is the honest motion for still hot air over a parking lot or above a candle. The default Noise Speed = 1 is a lively boil, Noise Speed 0.2–0.5 the slow heavy churn of a large heat mass, Noise Speed = 0 a frozen field. Wind Speed drifts the whole field instead and Wind Direction sets which way it goes — scrub the angle with Render on Field and stop where the drift runs the way the air should. Useful wind numbers are small, and the working band sits below the default Wind Speed = 1: Wind Speed 0.2–0.8 covers everything from a barely-moving column to a steady plume, negative values reverse it, and the slider’s outer reaches are streaming-energy territory rather than heat. A convincing plume is almost always both dials at once — wind alone reads as a texture sliding past the camera, evolution alone as a static volume of air that happens to be boiling.

Mask confines the shimmer: assign any layer and the effect follows that layer’s matte, so it fades where the matte falls off instead of stopping at a hard edge. Left at none it renders over the whole frame — the default, not a bypass. Mask Mode picks what the matte reads: Alpha for a shape layer or a rendered element with real transparency, Luma for a painted grayscale plate, usually the fastest route — a white blob over the exhaust on black, feathered wide. Inverted Alpha and Inverted Luma are for when the easier region to paint is the one you want protected.

Render is the diagnostic popup, and using it is most of what makes this effect quick to dial. All is the finished result; Displacement and Heat isolate one stage each; Field shows the noise field itself in grayscale, the fastest way to see what Noise Scale, Noise Gamma, and Noise Aspect are actually doing. Field to Alpha is a different proposition entirely: the field is written into the alpha channel, and the effect stops being a filter on a plate and becomes a generator you can composite — a boiling, drifting matte with its motion already built in. Give it a layer with real color variation to work on; there’s nothing for either stage to bend or soften in a flat solid, and you’d get the matte with a dead interior.

The four macros ride the look you already struck, and 100 is neutral on each. Master Amount multiplies Distortion Amount and Heat Amount, each on its own fold — the dial to keyframe when shimmer should build as something heats up, since bend and softening then arrive in the proportion you set by hand. Master Speed multiplies Noise Speed and Wind Speed: one value for churn and drift when a shot gets retimed, and the ratio you struck between them survives the move. Master Scale multiplies Noise Scale, resizing the field’s features and nothing else. Master Complexity multiplies Noise Complexity — take it down while you work a heavy comp, back up for the final.

Ride either the macro or the dials it folds, never both: keyframe a macro and its underlying dial at once and the scaling compounds. Master Amount = 0 zeroes both, which makes it your A/B against the untouched plate and a clean place to keyframe from when the shimmer should arrive out of nothing.