Brush dynamics
One row per parameter, a sensor on the row: how pressure, speed, tilt, stroke direction, barrel rotation and randomness push a brush around as you paint, and how to reshape the response behind each one.
Brush Studio ▸ Dynamics is a list of the twelve things a sensor can drive. Every row is the same: the parameter's name, a signed amount, a sensor dropdown and a curve button. The sensor is what switches the row on: at None the row is inert and the base value passes straight through.
All of it lives on the preset, so it travels with the brush.
The twelve rows
| Row | What the sensor drives |
|---|---|
| Size | Dab diameter |
| Accumulation | The stroke's tone ceiling |
| Flow | How much paint each dab lays down |
| Rotation | The tip's angle. This one row is angle jitter, direction-follow, tilt-follow and barrel-follow at once: which of them you get is simply which sensor you pick |
| Scatter X | Offset along the stroke's direction |
| Scatter Y | Offset across it |
| Hardness | Tip edge softness. Procedural tip only |
| Shape | Roundness of the procedural tip. Procedural tip only |
| Hue | Per-dab hue shift |
| Saturation | Per-dab saturation shift |
| Luminosity | Per-dab brightness shift |
| Impasto | How thickly paint is deposited. Only alive on a Paint behaviour |
The nine sensors
| Sensor | What it reads |
|---|---|
| None | Nothing. The row is off |
| Pressure | Stylus pressure, 0 at no contact to 1 at a full press. A mouse or a finger with no pressure sensor reads as a full press |
| Velocity | How fast the pen is moving across the canvas, normalised |
| Tilt | How far the pen is leaning, in any direction |
| Direction | The stroke's heading, running 0 to 1 over a full turn |
| Random | A fresh value per dab, hashed from the dab's position so the same stroke re-renders identically instead of shimmering on every redraw |
| Fade | Ramps from 0 to 1 over the first stretch of the stroke, then holds. How long that stretch is comes from Fade Length |
| Random (stroke) | One random value for the whole stroke instead of one per dab, so each stroke differs from the next but stays even along its length |
| Barrel rotation | How far you have rolled the pen in your fingers, running 0 to 1 over a full turn. Only pens with a rotating barrel report it. On any other pen the value stays at 0 |
Fade Length appears in the General tab as soon as any row uses Fade. It is measured in brush widths, from 1 to 200, so the same number gives the same ramp on a 4 px pencil and on a 200 px wash.
On the Rotation row, Direction, Tilt and Barrel rotation rotate the tip BY the sensor itself rather than multiplying something by it. That is what keeps a flat nib perpendicular to the stroke, lying over with the pen, or turning as you roll the pen. A pen that reports no barrel rotation leaves the tip where it is. The curve there only shapes how strongly.
The amount is signed
The amount runs from -100% to +100%, and the sign is the point. A positive amount can only shrink the base value, toward 1 minus the amount; a negative one can only grow it, toward 1 plus its size. Pressure thinning a dab and tilt widening one are therefore the same control with opposite signs, rather than two separate settings.
An amount of 0 contributes nothing whatever the sensor says, which is a normal thing to want while you are tuning.
The curve
The button at the right of each row opens the response curve. A Linear tick at the top bypasses it entirely: the sensor maps straight onto the parameter. Untick it and the curve you draw shapes the response instead.
Under the curve sits a strip of ready-made profiles, Linear, Ease In, Ease Out, S-Curve, Sharp and Flat, so a shape is one click rather than a drag-the-points exercise. Picking Linear from the strip also re-ticks the Linear box.
Click empty space inside the curve to add a point, drag a point to move it, right-click an interior point to remove it. The two end points are locked to the left and right edges. The line drawn through your points is monotone, so it can never overshoot and double back between two points you placed.
Stacking a second sensor on one parameter
A parameter can be driven by two sensors at once. Right-click a row and choose Second layer: a second row unfolds under it, starting on Pressure at 25%, and you can point it at any other sensor. The pencils rotate the tip by stroke direction AND pen tilt together, which one row cannot say. Right-click again and choose Remove to take it away.
Layers compose by product, so two sensors both shrinking a dab multiply rather than fight.