Stroke engines (Paint)

Pick how your strokes are computed: Analytic for clean, unbounded, cheap strokes; Sequential for wet effects — smudge, rub and contrast — where every dab sees what the previous dabs painted; Stamp to paint with a captured region of the canvas as the brush footprint.

The engines

The engine picker sits directly under the stroke-operation buttons at the top of the Brush panel.

The engine picker row: Analytic | Sequential.

Analytic — the default. Strokes are computed in one closed form, so they are seam-free at any length and cost the least. The parameter grid shows only the parameters this engine uses.
Sequential — strokes are simulated dab by dab in order. That order-dependence is what makes self-referential effects possible, and it unlocks four extra parameter rows: Wetness, Trail, Rub and Contrast.

The parameter grid with the Analytic engine active — only the analytic rows show.

The same grid with Sequential active — Wetness, Trail, Rub and Contrast join the set.

Switching engines swaps the parameter grid's rows (each engine remembers its own row order), the stroke preview re-renders with the engine you picked, and saved stroke presets remember which engine they were made with.

Wetness and Trail (the wet brush)

On the Sequential engine the brush carries a reservoir — the color it is about to deposit. Two rows control it:

Wetness — how much of the stamp color comes from the canvas under the brush vs from your picked ink. 0 = pure ink (a dry brush); 1 = pure canvas pickup (a smudge tool that adds no ink of its own); 0.5 = an even mix. It is a share, not a rate — 0.01 really is a barely-there tint.
Trail — how long picked-up color smears after the brush leaves it. Low trail: the reservoir follows the canvas almost instantly. High trail: color you crossed several brush-widths ago still tints the stroke.

The pickup samples the whole brush footprint, weighted by the brush's own hardness profile — a soft rim drinks less than the hard core — and transparency counts: with Wetness at 1, stroking across empty canvas deposits nothing until you cross paint, then the paint smears out over the trail length.

A red wetness stroke (Wetness 0.85, Trail 0.7) crossing a blue band: the stroke drinks blue while inside the band and the picked-up violet fades out over the trail length below it.

The reservoir swatch in the Color section shows the carried color live while you stroke. Persist reservoir across strokes, in the Stroke category of the paint settings, keeps it loaded between strokes instead of re-inking at pen-down. Reset reservoir now, in the same category, re-inks it immediately.

Stamp — paint with a captured region

The third engine paints with the stamp bin's current stamp as the brush footprint — grab a region of your canvas in Stamp mode, activate it in the bin, pick the Stamp engine, and every deposit is that image, scaled so its longest edge equals Diameter. Edges come from the stamp's own coverage, so the Hardness row hides; the grid shows Diameter, Opacity, Spacing and Blend X. See Selection & stamps for capturing and the full behaviour.

The preview follows the engine

The stroke preview renders with the ACTIVE engine — with Sequential selected, enable a background pattern (Options ▸ Background) and the preview shows your wetness/rub/contrast settings interacting with that pattern exactly as they would with canvas paint.

The stroke preview rendering the same wet brush over the enabled background patterns.

Where did Deposit and Carry go?

They merged into this model (2026-08): Carry became Wetness (same intuition, but now a true mix share), Deposit's ink-amount role is Wetness's ink share, and coverage/transparency is what Opacity always was. The pickup blend-mode picker is gone — pickup is a straight spectral mix.